Wikipedia:Reference desk/Science

August 15

xenalights

information on xenalights as a air cooling technology —Preceding unsigned comment added by 72.222.165.50 (talk • contribs)

Xenalight makes a type of fiberoptic light. I do not know of any other product they produce. I do not know of any means of cooling with fiberoptic lights. -- Kainaw^(what?) 03:04, 15 August 2007 (UTC)

Hmm - I agree - it's a fibreoptic light. One claim for such lights is that they can deliver a lot of light without producing a lot of heat becaused the hot lamps can be placed a long way away and the light they generate carried to where you need it down the fibre bundle. So they don't cool the air, but they presumably do a great job of avoiding heating it up. SteveBaker 03:53, 15 August 2007 (UTC)

Cardio and Barfing

I have been doing a lot of intense cardio for the past 6 months, and recently I feel like barfing while running and I cant figure out why. I think its because I drink too much water before and during, but I have always drank a lot of water. Any ideas as to why I'm feeling like this? Thanks —Preceding unsigned comment added by 76.167.145.55 (talk • contribs)

... perhaps there is a difference between "intense" and "too intense" ...? something to consider ... (Joseph A. Spadaro 03:16, 15 August 2007 (UTC))

Motion sickness? Um, don't ask medical advice here, talk to your doctor. ←Ben^B4 03:44, 15 August 2007 (UTC)

I think we are getting a little too broad in our categorizing of questions under medical advice. This issue could certainly be discussed from a theoretical standpoint. Why would one feel nauseous while exercising? Mrdeath5493 04:09, 15 August 2007 (UTC)

I used to play soccer at a fairly competitive level and our coach would often make us run to the point where people would vomit. There's also anecdotal evidence linking intense cardio and vomiting with lactic acid build-up. Heat exhaustion, altitude, or simply overdoing it could also be relevant factors. Also, maybe read this [1]. The preceeding does not constitute medical advice, consult your physician, etc. -- 38.112.225.84 04:52, 15 August 2007 (UTC)

The cardio I used to do was way more intense, actually thinking about it, what I'm doing right now isn't really intense. I never really had this problem before, I think if it was motion sickness, it would have been present in the past.

I know when pushing too hard I use to get nauseous, but never when I was not pushing too hard or too long.

Same altitude in an air conditioned gym (I dont really even sweat a lot, well not excessively. Thanks for the article and everyones help.

I seriously disagree. When someone says "I'm exercising and I'm having these problems" they really need to see a doctor and we should tell them that. Discussing stuff from a 'theoretical' viewpoint in a case where someone needs to see a doctor it a very bad idea! Perhaps if the poster had said "I was speaking to a person I met in the gym and he said he was exercising a lot and..... This got me thinking, what could have caused this person's problems", then probably discussing things from a theoretical view point would be okay. (but please don't take this as an example to phrase your question so). Nil Einne 11:15, 15 August 2007 (UTC)

It could simply be a bad case of acid reflux from all that water, indeed.

This could be a brain tumor, too. Again, see a doctor. ←Ben^B4 17:49, 15 August 2007 (UTC)

You are telling us that something has changed which could have a serious cause. You really need to see a doctor so it can be checked out. Skittle 18:56, 15 August 2007 (UTC)

See this. Of course he needs to see a doctor, but that doesn't mean that the topic is off limits, does it? Are we to never mention nausea and exercise together again? Does it need a new thread? After 3 people declare that we can't give this person specific medical advice and to see a doctor, it seems perfectly acceptable to discuss this exact topic theoretically. I personally have nothing to add, because I'm not familiar with why this would happen. However, I fear that others who might be able to contribute something are being improperly discouraged.

Furthermore, if you actually read the Medical Disclaimer, you might notice that it does not prohibit such discussion. It just warns users to seek professional advice and not to rely on information submitted by users. It certainly seems to license theoretical discussion, rather than forbid it.
Mrdeath5493 19:31, 15 August 2007 (UTC)

The medical disclaimer applies to articles - the ref desk has different rules - one of which is: "The reference desk is not a place to seek professional advice on medical or legal matters, nor analyses, diagnoses or solutions to questioners' health or legal problems, and responses that could be construed as such must not be given." - so, nothing that could be construed as a diagnosis is allowed - which would obviously include "It could simply be a bad case of acid reflux". Writing a referenced article about some medical matter is OK - but issuing a diagnosis of a particular patient is to practice medicine without a license - which is illegal in many places in the world. SteveBaker 19:57, 15 August 2007 (UTC)

There must be some circumstance under which we could theoretically discuss cardio and barfing. What are the boundaries? Not under this thread? Not within so many days of the asked question? Is some sort of disclaimer at the beginning of an answer required? Or is it just off limits forever since someone asked about it in a way that seemed to be seeking medical advice (certainly not, I assume)? Don't think I'm being snarky, either. Discussing this can not be completely off limits. There just needs to be some explicit way of indicating that we are not giving medical advice. (I think the medical disclaimer is enough, but whatever.) I'm not sure anyone wants to diagnose or treat OP's that ask questions like this. These sorts of questions raise curiosity (at least they do in me) and I would like to see some sort of educated response. I think that people that are capable of answering such questions (from a standpoint that in no way diagnoses or treats the OP) are being unjustly discouraged

Mrdeath5493 00:19, 17 August 2007 (UTC)

I think the rules are pretty clear. Here on the reference desk, we are answering one specific person's question - and the advice we give could therefore be interpreted (by some blood-sucking lawyer) as diagnosing that persons medical condition. That's a no-no. Over in article space, we are not talking to a specific individual - we're obviously talking in general terms which means that we haven't heard a specific individuals list of symptoms and we can't possibly be said to be diagnosing that individual. A disclaimer that tells people who read that article that it's not specifically talking about them is legally defensible (we hope!) - but that disclaimer simply can't work here where we most definitely are giving medical advice to someone who came here to ask about their symptoms. So here on the ref desks - GIVE NO MEDICAL OR LEGAL ADVICE. It's a rule - it's a really simple rule. I think it's quite impossible to talk about cardio & barfing "in general terms" when we're responding to a particular person who claims to have those exact symptoms. Like it or not, what you say COULD be interpreted as offering him advice - which is flat out illegal in most places in the world. Perhaps there are some weasel-words that might get around that - but precisely because that is such a vague thing - and because Wikipedia itself could get dragged in as you get sued, we have to have a rather over-arching set of rules just to be on the safe side. So - discussing this most certainly can be off limits (and I believe it IS off limits in this case). You may think the rule is a bit over-the-top and that some improvement to it could be made - and I'm sure there is a forum where that can be discussed - but the rule is currently what the rule is, and you shouldn't break it. Look - it's only a matter of time until someone asks a medical question, someone here says "oh - this happens all the time - don't worry about it" (or something like that) - then, comforted that this is nothing, the person doesn't go to the doctor and subsequently dies. His grieving parents (or perhaps their insurance company) examine his PC's browser cache looking in desperation for anything that can explain their loss. They find the Wikipedia question - and find the answer given here - and in a fit of grief-stricken rage (or profit-driven search for a way to weasel out of a $5,000,000 payment) decide to sue Wikipedia. Wikipedias lawyers examine the situation and discovered that you violated the ref-desk's rules - as clearly laid out and often discussed here. Now the lawyers of (the insurers of) the parents of the dead kid turn on you - and in whatever state you and they live in, there is a law that says it's illegal to perform medicine without a license. Now YOU, PERSONALLY are being held liable to the kid's death - that's involantary manslaughter - you spend a large fraction of the rest of your life in jail and the accompanying fine bankrupts your wife and kids. Yeah - that's how serious this is! So - by all means campaign for a change in the rules (I'll be strenuously opposing you - so will others - which means you won't get a consensus for a change - so it won't happen). But right now, you have to obey the rules. I think we should take this more seriously - I think we need an admin to start handing out 24 hour bans to people who violate the rule so it's taken more seriously. SteveBaker 03:16, 17 August 2007 (UTC)

Well, at least I made my point clear. From the standpoint of practicality, you have swayed me. Although the situation you described is highly unlikely, it is totally possible. For it not to happen, I guess the structure of the rule in question should be overprotective. In a risk/reward analysis, there is comparatively little to gain and too much to lose.

On a side note, I got my undergraduate in Philosophy. Excellent argument. Too bad your not a lawyer...

Mrdeath5493 05:35, 17 August 2007 (UTC)

Journal Cell Publication Period

Is the journal "Cell" published biweekly or bimonthly? The disambiguation page for the word "cell" says it is bimonthly, but I understand it to be biweekly, which is what the main article says. Is there a difference I am missing, or can I change this? 131.215.240.27 03:28, 15 August 2007 (UTC)

It's published biweekly (every two weeks). I'll change the disambiguation page. Flyguy649 ^talk _contribs 03:32, 15 August 2007 (UTC)

There is general confusion over bi-, some people using it as "twice-" and some using it as "every two". There is a similar confusion over semi-. It might be worth avoiding using these prefixes where possible. Capuchin 08:16, 15 August 2007 (UTC)

For biweekly you could use fortnightly I guess but what about bimonthly? Every two months? Bimestrial is probably more confusing. The confusion may partial arise from biennially I guess Nil Einne 11:06, 15 August 2007 (UTC)

Glazing

what is segar formula,please elaborate —Preceding unsigned comment added by Naray2007 (talk • contribs)

Do you mean agar? Lanfear's Bane

Or sugar? Capuchin 11:49, 15 August 2007 (UTC)

A quick google turns up that it's something to do with the chemical composition of pottery glazes. Nothing stands out as being particularly enlightening, though. 147.197.230.174 11:58, 15 August 2007 (UTC)

According to [2]:

Segar Blue Glaze - cone 9-10

(KPG)

3360 G-200 feldspar

1440 whiting

1040 ball clay

2160 flint

240 rutile

320 red iron oxide

----------------------------------------------

8560

(I hope this means more to our OP than it does to me!)

SteveBaker 12:42, 15 August 2007 (UTC)

I was thinking more of glazed doughnuts (mmmmmm). Capuchin 13:09, 15 August 2007 (UTC)

If you like your doughnuts glazed in ground up flint and red iron oxide...go ahead. If you're hungry, I think there is still some of that cookie left - about five posts up from here. SteveBaker 13:13, 15 August 2007 (UTC)

READING BURRETTES IN TITRATION

Assuming you are given a 50litres burrate which are not callibrated stepwiselly i.e each location isnt labeeled, can u take the burrete reading in the opposite direction knowing well that you will arrive at thesame answer. i.e

INITIAL READING 50.00 35.00

FINAL READING 35.00 15.00

Knowing well that the reading of a callibrated burette is

00.00 15.00

15.00 30.00

BUT IT IS STILL THEASME VALUE OF ANSWER.

OKEWOLE OLUWASEYI

—Preceding unsigned comment added by 80.88.140.24 (talk • contribs) 10:51, 15 August 2007

If you mean what I think you do, yes, it's the difference between the values that's the titre. (Also, a 50 litre burette?) 147.197.230.174 10:57, 15 August 2007 (UTC)

I somehow think a mili was missing from somewhere. Nil Einne 11:00, 15 August 2007 (UTC)

Wow! A coral atoll (click on the link) was missing? Maybe you mean a milli...? :-) Carcharoth 16:22, 15 August 2007 (UTC)

One half of a lip-synching vocal duo? Edison 17:59, 15 August 2007 (UTC)

Internet in Africa

I'm looking for a map that shows the distribution of internet access (or something along those lines) in Africa. My dream would be to find something about cross-border internet connections in Africa (who's communicating with whom, etc.), but I doubt there's anything about this topic in particular. So any type of map in that direction would be interesting: Internet access, internet usage, possibly the most important internet cables (i.e. hardware), you name it.

Do you have any idea where to find that kind of materials? Thanks, Ibn Battuta 16:55, 15 August 2007 (UTC)

PS: I'd rather use materials that do not just display information for each country; if possible, I'd like to prevent using political borders as sorting criteria. Thanks, Ibn Battuta 17:02, 15 August 2007 (UTC)

Many areas in Africa are not well served by terrestrial Internet, but there are at least ten separate providers of satellite IP service taht covers all of Africa. When you use satellite service, each terminal is topologically "closer" to the hub and the the Internet core than they are to each other: the ping time from such a terminal to Wikipedia is approximately half the ping time to a terminal in a village 20 km away, and the IP addresses reflect the IP address space of the hub, not the African country. Each ISP's hub can be anywhere that is visible to the satellite, e.g. in Europe. Of course, much of the population will be in larger towns and cities with terrestrial internet connections ranging from poor to excellent. -Arch dude 17:21, 15 August 2007 (UTC)

The Internet isn't like the telephone network. You can't tell who is talking to whom by looking at a wiring map of the Internet - there is no way to know whether the bulk of the traffic from (say) South Africa is going to Wikipedia's servers or in local communications or in communications with users in (say) Kenya. Even if people in Kenya and South Africa were talking to each other in great numbers, the odds are good that they'd be using Gmail or MySpace to do it - so the actual communication pathways would probably still go to big servers outside of the African continent even if two people in the same town were talking to each other. For example - my sister and I use the same mail server (my Webhosting company gives me 700 free email accounts - so why not?) - but she lives in UK and I live in USA. When she emails her neighbour, the email travels from UK to USA, where it sits on the server and is then sent off to the neighbour in UK - how could you possibly tell the difference between a communication between two people in the UK and a communication to a location in the USA? You are asking a question that cannot be answered - even in principle. SteveBaker 17:37, 15 August 2007 (UTC)

Maybe I didn't express myself clearly enough: I'm looking for maps, not just general information. :o) And yes, I'm very aware that the internet doesn't work like the phone, that's why I said the information is probably not available. (It would require extensive surveys, which are probably not even available for industrialized nations.) So the other option are maps of 1.) hardware (e.g., those hubs -- are there maps about their distribution? Else I've found so far only this map) or 2.) statistics (how many households use the internet, how many hours/week or /month do people spend online on average etc.). Thanks, Ibn Battuta 18:18, 15 August 2007 (UTC)

Hole in a spacesuit

An astronaut doing a spacewalk had to return to the shuttle early today because of a tiny hole in the outer layer of his glove. That got me thinking -- just what would happen if that tiny hole had penetrated through all the layers of the glove? Would the astronaut had suffocated (as would happen with no spacesuit at all)? -- Mwalcoff 22:46, 15 August 2007 (UTC)

A micrometeorite, a sharp edge from a broken piece of metal or a tool, or even the end of a piece of wire could cause a puncture. The NASA Extravehicular Mobility Unit, the space suit used on extravehicular activities is apparently one large pressurized system, and a leak anywhere would soon bleed away the oxygen needed to sustain life.[3] The life support system would release stored oxygen, so the size of the hole which cause a leak would be an important factor. A pinhole would lead to a sudden end to an EVA and a race for the airlock. A large cut might be catastrophic. In sci fi stories, there were devices such as pressure cuffs in space suits which could be suddenly inflated to seal off the hand, foot, arm or leg which had the leak, preserving life at the cost of injury to or loss of the isolated part. Again, time would be of the essence. The suit reportedly has only 4.7 pounds per square inch, less than 1/3 of normal Earth air pressure, so direct pressure on a puncture would slow the leak. A sticky patch (think NASA quality duct tape) held on with pressure could seal many leaks, but I have not seen that they have that readily available. They do have a rule to inspect the gloves every half hour because of tears found in the past which penetrated the outer layer. Self sealing suit and glove materials have been developed which have in the lab sealed 2 mm holes, with research ongoing to extend the capability to 4 mm holes [4]. This self-sealing capability would add 15 pounds or 5% to the EMU mass, an would increase the mass much less if only applied to the gloves, but making the gloves thicker without losing dexterity might be a challenge. I would at least go with Space Duct Tape. Edison 23:11, 15 August 2007 (UTC)

Michael L. Gernhardt was aked this question. [5] His response:

"If we got a small hole [in our spacesuit], our oxygen would start coming out of the spacesuit, and the pressure would start to drop. If the pressure drops too far, then you'll get the bends, and if it drops below about 2.5 psi, then you don't have enough oxygen to maintain useful consciousness. Now, we have a device called the Secondary Oxygen Pack on the back of our backpack, and it's got a whole lot of oxygen in it, and it would be able to support a small leak for—depends on how small it is—but for at least 30 minutes. So for a small leak, we'd have our secondary-oxygen system kick in, and we'd be heading back to the airlock and repressurizing, and we'd be fine. A big leak—like a big hole in the suit, say a half-inch hole or something like that, or if your glove blew off—would pretty much be a real bad day for you." Rockpocket 23:15, 15 August 2007 (UTC)

I'm sure I remember reading that very small holes to appear in suits and they are not noticed until returning to the space craft, because they are too small (i mean bordering microscopit) to notice or to have much effect. SGGH ^speak! 00:17, 16 August 2007 (UTC)

I'm not answering the initial question here but you may want to google self healing polymers which can potentially heal damage to their structure many times... try [6] for a bit of interesting info. --Cosmic joker 00:47, 16 August 2007 (UTC)

In the movie Event Horizon, one of the crew members goes into an airlock and floats out into space without a suit. Blood comes out of his eyes and stuff. They get him back and he survives. Is that survival realistic? --Seans Potato Business 00:36, 16 August 2007 (UTC)

See Vacuum#Effects_on_humans_and_animals, Human_adaptation_to_space#Effects_on_humans and Explosive decompression. Exxolon 00:50, 16 August 2007 (UTC)

Something similar happens in various moments throughout the Gundam franchise, Generally someone closes their eyes and covers their ears, opens something suddenly enough that the oxygen rushes out and 'manages to survive' by staying within the oxygen stream until they get to whatever they were jumping to (which generally is only a few seconds) --Lucid 02:35, 16 August 2007 (UTC)

So the aptly named scientist Robert Boyle put small animals in a vacuum and observed the effects. Perhaps they felt "ebullient." The scene from "2001 Space Oddesy" is plausible, in which a man survives brief vacuum exposure. Edison 04:04, 16 August 2007 (UTC)

You would think that NASA could just have astronauts wear a standard high altitude type masks insider their helmets. Then even if there suite was punctured they’d still get oxygen. Yes, the person might suffer decompression sickness and might eventually freeze to death after a long while, but they would have a much greater chance of making it back to the lock or being rescued. --S.dedalus 06:19, 16 August 2007 (UTC)

S.dedalus, that's exactly what I'm wondering: Can you survive in vacuum as long as you can breath and don't freeze to death? If so, I really don't understand why they don't have a two-part suit, with a mask for oxygen, and mere heating for the rest (plus a bit of pressure as long as necessary). I'm sure that NASA debated that at some point and apparently rejected the idea. So is a vacuum just below the pressure that a human body can survive? Or what is the problem? --Ibn Battuta 07:53, 16 August 2007 (UTC)

The standard NASA and Russian suits have been filled throughout with one zone of breathable gas, pure oxygen at relatively low pressure. The low pressure may make it easier to move around, since the curse of space suit design has been that if bending reduces the total volume, the gas pressure resists the movement. A lot of cleverness has gone into making joints such that bending the arm or leg does not cause a volume change. A new proposal, "skin tight suits" is discussed in Space suit. These would have a skin tight pressure garment (with heating or cooling, naturally) surrounding the body with a gas supply only to the face. That way, movement would not be opposed by the gas pressure. If such a suit were punctured, there could be tissue damage from fluid exposed to the vacuum boiling, or from simple blood loss accelerated by the lack of external air pressure, but see the "space duct tape" notion above for possible repairs. There are sharp edges from rocks on the moon and mars as well as when working with equipment in extravehicular activities. If there is ever conflict in space, it would be useful to not have an impact from a small projectile not be inevitably quickly fatal. A Mars explorer with a hole in the arm of the skintight suit (which did not threaten the continuity of the breathing air supply) could rescue himself much more easily than if the oxygen were rushing out at a rate which dropped the breathing supply to too low a pressure to sustain life, or which quickly used up the supply in the tank. Such a suit would have to have a moisture absorbing layer, to allow the skin itself to "breath" by expelling moisture. The present suits have a life supprt system which absorbs this moisture. Edison 16:10, 16 August 2007 (UTC)

The only known suit puncture was partly sealed by the astronaut's own blood (on STS-37 [7]). And wasn't noticed until examination back on Earth so a puncture need not be catastrophic. Rmhermen 01:18, 17 August 2007 (UTC)[8] Rmhermen 01:18, 17 August 2007 (UTC)

August 16

Stupid pharmaceutical names..

Where do the ridiculous names like 'Gemtuzumab ozogamicin' come from? It it's a Calicheamicin-(another one!)-bound anti-CD33 antibody then call it that! Don't tell me that Gemtuzumab ozogamicin is less cumbersome! --Seans Potato Business 00:30, 16 August 2007 (UTC)

Monoclonal antibodies for therapeutic use have a specific nomenclature. See Nomenclature of monoclonal antibodies. I agree it looks crazy, but the name is actually quite inforamative. I imagine IUPAC has rules for naming other compounds, but I'm not sure. Flyguy649 ^talk _contribs 00:40, 16 August 2007 (UTC)

Full IUPAC names would be a terrible mess for drugs—while they would describe the drug structure completely, they'd never fit on the label for any but the very simplest molecules. Instead, standardized generic names are created based on a set of standardized stems, prefixes, and suffixes to create International Nonproprietary Names and United States Adopted Names. TenOfAllTrades(talk) 01:25, 16 August 2007 (UTC)

Wikipedia has an article List of chemical compounds with unusual names about real chemicals with funny names, such as "curious chloride," "traumatic acid," "moronic acid," and "draculin, an anticoagulant found in the saliva of vampire bats." There was a strange scientific paper which sought to determine "Is an Arsole aromatic?" Edison 04:17, 16 August 2007 (UTC)

The names are choosen to be stupid and long and hard to remember! The producer with patent for the medicament (chemical substance) is allowed to choose two names, one for the own business, mostly easy to remember, and than an second name used for the other producers after the patend has run out or the product is licenced to somebody else.--Stone 09:37, 16 August 2007 (UTC)

How long would you retain consciousness/awareness if your head was cut off?

Simple enough question. If your head was severed from your body, (for the sake of argument lets say this is almost instantly), how long would a person retain consciousness/awareness (assuming the shock didn't kill them instantly). Could someone cut your head off and show your headless body to you before you lost consciousness for instance? Exxolon 00:46, 16 August 2007 (UTC)

Have a read of the articles decapitation and guillotine, they answer those questions. Since the effectt is always quickly fatal, there is no real way of knowing, movement and supposed reaction has been observed in severed heads immediately after the act, but no one can tell if they were purely physical/reflex or conscious movement. For quite obviousl reasons there has been a lack of research in this specific field. Vespine 00:57, 16 August 2007 (UTC)

au contraire our fascination with death has, in fact, lead to some experimentation on the subject. Plasticup ^T/C 13:47, 16 August 2007 (UTC)

I think this more a humanities question but there have been arguments about how long it takes for brain death to REALLY occur when oxygen is cut off from the brain for a long time. If your head is cut off I'd guess you would lose 'consciousness/awareness' as opposed to brain death in fractions of a second of the spinal cord being severed. If you've ever had a really nasty knock/shock you lose all awareness. When I was a child I fell off a roof and was knocked unconscious (big surprise) so I had no awareness, I could have died that day and would have had no awareness that I was lying starfished on the ground so my awareness would have ended when I hit the ground. But (and I said this was a humanities question) the perception of how long it takes you to lose awareness may be very different. --Cosmic joker 01:13, 16 August 2007 (UTC)

Part of this question borders on a sort of philosophical / semantic debate about what it means to be conscious. To simplify the issue, we could define a standardized test for responsiveness of some type. Then, simply perform that test on the head. Such a test might need to be specifically crafted given the uniquely limited communications capabilities of a severed head. Nimur 01:48, 16 August 2007 (UTC)

Henri Languille responsiveness was measured by his opening and closing and focusing his eyes. Carcharoth 03:29, 16 August 2007 (UTC)

Nobody has yet mentioned Mike the Headless Chicken?! For shame! You should all have your Wikipedia editing privileges revoked D: --Lucid 02:04, 16 August 2007 (UTC)

The question has also been covered by the great Cecil, briefly in this article and more extensively in this followup. —Steve Summit (talk) 02:15, 16 August 2007 (UTC)

Ooh. That last story is horrible! It should be possible to carefully decapitate without using a large impact that would render someone unconscious, but then you get into the realms of science fiction and 'heads in a jar' type things. Carcharoth 03:37, 16 August 2007 (UTC)

More specifically, don't miss Guillotine#Living heads! :-) Carcharoth 03:37, 16 August 2007 (UTC)

nickle silver alloy

nickle silver alloy combination is 55% CU 27% ZN 18% NI my question is what is the withstand temperature of this alloy (that is in which temperature itss colour will be change

Does Nature utilize prime numbers (qua prime) for any reason?

I know that the American periodical cicada has two sub-species, one which resides underground for 13 years and the other for 17. Apparently, these numbers were selected by evolution because, being prime, they make it difficult for any predator species to correlate their own life cycles to those of the cicada. For example, had the cicada’s periodicity been 12 years, then any predator species having cycles of 2, 4, or 6 years could prey on them. I am wondering if this is the only example of prime number utilization in Nature, whether it is in the organic or inorganic domains. Humans now use primes in encryption, a practice broadly analogous with that of the cicadas. But, before computers, was there any practical use for primes. Myles325a 04:25, 16 August 2007 (UTC)

Could predators could evolve to be in sync with one of the sub-species and thus have a predictable food supply? An alternative explanation I've heard is that having several reasonable-sized prime-number periods keeps more than one of the sub-species from appearing at the same time, thus preventing them from competing with each other for food or territory or whatever resources the noisy critters use. DMacks 04:36, 16 August 2007 (UTC) Meh, off-topic...scientists have apparently been arguing about the evolutionary reason for the length and primeness for a long time and don't appear to have good consensus. DMacks 04:46, 16 August 2007 (UTC)

If you count the number of seeds in a circle around a pineapple you will get a prime number. Also look at the sunflower seed head. This sort of thing happens when things are arranged in a spiral growth pattern on a plant. Frequetly the prime mumber is 2, or 5 but the large plant objects like fruit or flower heads could have larger prime numbers in use. Graeme Bartlett 05:56, 16 August 2007 (UTC)

OP myles325 back. Yep, Graeme, that's interesting, but I did specify "prime(qua prime)", in other words prime numbers BY VIRTUE of their primemess. Now, is this the case here? Do we find primes in spiralling entities, and if so why? Myles325a 06:14, 16 August 2007 (UTC)

Actually, I think in the case of natural spirals the tendency is more towards Fibonnaci numbers, it's just that four of the 6 smallest of them happen to be prime (counting the repeated 1 only once), and then after that the numbers are getting too big to be particularly likely to occur naturally. Confusing Manifestation 06:26, 16 August 2007 (UTC)

Yup, the Fibonacci number page (note spelling:) has some examples from nature. DMacks 06:35, 16 August 2007 (UTC)

The OP's example sounds like one given by Marcus du Sautoy in The Music of the Primes, and his Royal Society Christmas lectures. You may have access to this already and have got the example from there, but if not, it may well have more details. Cyta 07:18, 16 August 2007 (UTC)

OP myles325 back. No, Cytal, I was not aware of this site, but thanks, I have checked it, and the ONLY example it gives of "primes from nature" is this one of the periodical cicada, which you can find [|here]. Surprisingly, it is quite badly written. It appears that Nature makes abundant use of Fibonnaci numbers, but the humble cicada is the only organism to utilize the power of the prime. Nothing on primes in geology, physics, cosmology etc either, although there might be something in du Sautoy's book. Myles325a 04:46, 18 August 2007 (UTC)

Interesting thought (which does not answer your question): If a lifeform uses a prime/fibonacci number by virtue of it's prime/fibonacciness then that suggests that nature does maths. If it just a reaction to other lifeforms not using them, then the evolution of that would require doing maths. Whichever way around, nature selects numbers. So if nature does maths, then we are not unique in that ability. Another 'human uniqueness' down the drain. :) DirkvdM 07:23, 19 August 2007 (UTC)

Hibiscus

How is hibiscus distributed?

It is normally proagated by taking a cutting and sticking it in the ground with rooting hormone. Graeme Bartlett 06:09, 16 August 2007 (UTC)

Source of non-copyrighted image of plants

Could someone help me to find a non-copyrighted picture of guar bean and processed guar gum? E.g. are there any federal institutions having photos of plants? Thank you in advance, Timur lenk 06:13, 16 August 2007 (UTC)

Can you fault my logical and scientific proof for personal immortality?

It’s based on the Schrödinger’s Cat thought experiment. Suppose you have a person in that box instead of a cat. ( “Schrödinger’s Friend”). As before, random events determine whether the box is flooded with poison gas or not. As before, Quantum Theory says that BOTH possibilities exist until an observer looks at it, and then it snaps into one option or the other. Suppose YOU are the guy in the box, and you are recording what happens. You notice an INCREDIBLE THING! Each time the random event occurs, it always comes out in your FAVOUR! It’s like betting Heads on a coin toss a hundred times in a row and never losing once. That’s becoz it is logically impossible for you to observe and record your own extinction. The scenario where you live is the one you will always experience. Thus, if quantum theory is true, and it appears to be rock solid, I will ALWAYS and forever be observing and recording my own continued existence. I will see everybody else die, but never myself.

And what goes for me goes for all the other people too. In the Universe they end up in, they will see me die, but never themselves. Can anyone put a hole in this? You will need to know a little about Copenhagen Interpretation of Quantum Theory.

It’s a bit like the basic idea in the film “The Prestige”. SPOILER ALERT! When the magician gets access to a cloning machine, he makes a clone of himself each night as part of his act, and destroys the clone during the act. Now, the two versions of the magician are identical, but each night one of them dies. Nevertheless, the magician’s life and memory carry on unimpeded, because there is always ONE of him left over. Now think of the man in Schrödinger’s box. He would see the experiment that has a 50/50 chance of killing him played over and over, and yet each time he finds himself alive. Like tossing a coin hundreds of times and always coming up heads. In the wider reality, a version of him perishes each time the experiment is done. The existential reality of his life has continuity because if is carried forward by the surviving copy. Myles325a 06:46, 16 August 2007 (UTC)

Sounds something like Wigner's friend. DMacks 06:53, 16 August 2007 (UTC)

Take a look at quantum immortality. It all depends on how you interpret quantum mechanics. It's a clever idea, by the way, even though other people have thought of it before. --Reuben 07:03, 16 August 2007 (UTC)

Actually sounds more like Russian Roulette. You can play and write down whether you live or die. You will never write down that you are dead. But that doesn't mean you live. Plus, you treat death as a single event rather than a sequence of discrete failures of body systems. What you will see in your scenario is your body and brain failing in sequence on a march until death (i.e. heart fails, levier fails, muscles fail, stomach fails, etc). Your scenarios is most likely a fate worse than death as you continue to live in a less and less capable shell. --Tbeatty 07:06, 16 August 2007 (UTC)

I don't know about the quantum mechanics aspect, but one thing seems hard to deny, "I will see everybody else die, but never myself." Still, never seeing yourself die doesn't necessarily mean "I will ALWAYS and forever be observing and recording my own continued existence." As an analogy, consider falling asleep. Replace "dying" in this thougt experience with "falling asleep". Does it follow that not observing your own falling asleep means you are forever awake? Pfly 07:20, 16 August 2007 (UTC)

You might also be interested in solipsism. It's perfectly rational that I am immortal --Lucid 11:23, 16 August 2007 (UTC)

I've thought a lot about this - and certainly what you describe seems possible within our present understanding of quantum mechanics. There are other interpretations of what we know that says it isn't true - but I'm not aware of any science that says it's impossible. A way to have personal immortality without messing around with all that religious stuff about after-lives initially seems very attractive and comforting. But remember that the 'anthropic principle' is the only thing that ensures that "you" always end up in the universe where you are still alive. But you only have to be sufficiently alive to "observe" events - and things around you would go on as normal. This principle won't prevent non-fatal injury so expect to lose arms and legs in car accidents - but to somehow always survive. You can lose your eyesight - your hearing - your sense of smell and touch. Everyone and everything around you can fizzle out. So you could be the only thing left alive in the universe - with just a portion of your brain operating and essentially nothing else - you could be in continual anguished pain and have no way to end it because anything you could possibly do to kill yourself will always fail. You're being kept alive by a continual series of increasingly unlikely coincidences - you can be starving and on the point of dying of thirst - and every thousandth of a second (say) just enough nutrition and water will appear (somehow) to just keep you alive for another thousandth of a second. After a couple of hundred years of life - you are going to be in the most terrible state imaginable. This is more like the classical vision of a personal hell than it is of immortality "the good way". We'd all better hope this isn't true. But read quantum immortality, quantum suicide, Final anthropic principle for more information. SteveBaker 11:44, 16 August 2007 (UTC)

Well, that's obviously wrong, your claiming its impossible to die if nobody is recording it. Also, you'll die of natural causes anyway, even if the box doesn't kill you you'll still die. ΦΙΛ Κ 18:20, 16 August 2007 (UTC)

No - you can't hand-wave this theory away so easily. Quantum theory shows that at the very lowest level of matter, events that can come out two ways don't just randomly come out one way or the other - both ways happen at the same time - and it's only when we try to measure the outcome that things settle down to one or the other answer. There are at least two ways to interpret what's happening - one of which is the 'Many-worlds interpretation' that says that when the quantum event happened, a complete parallel universe was spawned - one result happens in "our" universe - the other result happens in the other. Thus, there are infinitely large numbers of parallel universes in which every possible outcome of every possible event down to the subatomic level are played out. It follows that if there is even a billion-trillion to one odds of you surviving that car crash, then somewhere with the multiverse, you'll still be alive. In fact, in an infinite number of the infinite universes you'll survive and in another infinite number, you're dead. Now comes the tricky part: Which of those sets of universes are "you" in? Well, the strong anthropic principle (which is another controversial - but possible theory) says that since you're here talking to us now, you must be in one of the ones where you survived. In some set of those universes, you'll miraculously survive every possible terrible event - even millions of years from now, insanely unlikely coincidences will keep you alive...and that's the universe you must perceive yourself as being in. Of course in versions of the universe that I survive in - you'll be dead and I'll survive. This seems strange - but nothing in science says it can't be true - and the parallel worlds version of what happens when quantum events occur is actually rather well accepted (although by no means universally). Dying "of natural causes" is just another random event - you can die because your heart stops - or a random fast-moving set of cosmic rays can just happen to strike it in just the right way to jolt it back into action...and if it fails again two minutes later - something else utterly miraculous will save you. Maybe the wonderous immortality drug is invented in your lifetime in some universes. Maybe aliens in other universes have selected you to be the representative of humanity who is saved when some global catastrophy wipes out the Earth. Sure, that's astronomically unlikely to happen - but we have a literally infinite number of parallel universes in which the event can just happen to come out right for you to survive - so not only is it POSSIBLE for you to survive in some of them - it's absolutely certain that you'll survive in an infinite number of them...if the many worlds hypothesis is true (which it may not be) and if the strong anthropic principle is true (which it may not be). The trouble is that most of the other hypotheses to explain the Schrodinger's cat thought experiment are every bit as weird and unlikely-seeming as this one. SteveBaker 02:42, 17 August 2007 (UTC)

That,s why I stick with the Copenhagen interpretation. In this situation, in the time between the potential nucleus decay and your reaction the wave function propagates, and then when you record either the poison release, or converse, it collapses into either the poison releasing and you dying, or it not releasing and the process continuing. I don't see how anything has been achieved here. ΦΙΛ Κ 16:22, 17 August 2007 (UTC)

OP myles325 back. Well, thanks to all for what was an impressive and high value response to Q. In line with my policy of talking right back, here goes:

1. DMacks. I looked up Wigner’s friend article, and ended up rewriting it, mainly for stylistic reasons, and then putting some queries / thoughts in the talk page there. You are welcome to look at it and see if I’m onto something, or up the wrong tree. In any case, Wigner’s friend bears on the topic, but not directly.

2.Reuben. You were one of several who pointed me to quantum immortality. I now see what I should have immediately known at the outset. And idea like this would have been chewed over many times before now.

3. TBeatty was one of several who pointed out that even if the reasoning was sound, it guaranteed immortality, but not any kind of health, which would ensure I would become even more decrepit than I am now. No one alluded to the ancient story of the man who asks the gods for immortality, and being granted it, now longs for death as he had not thought to insist on eternal youth as well.

4. PFly dropped a particularly robust fly in the ointment with his analogy of sleep. I can’t fault it as of now, though I sense there may be an out. But certainly, in sleep we lose consciousness, as we must do in death. Could I say that I will never experience sleep because at the moment of lapsing into unconsciousness, it would be that reality that included an “awake” version of myself which would inherit the continuity of my life? I don’t know.

5. SteveBaker was however, and again, the standout here. And his considered arguments, and links to various sites were illuminating and useful. Thanks Steve. Some thoughts. If there is literally NO chance of survival in ANY scenario whatsoever, like surviving a nuclear blast while being strapped to the bomb, then perhaps there is no alternative reality in which I live, and therefore I can then die. But perhaps in such a situation, the continuity of my life would demand that we go back down the tree structure of choices and alternatives that LED to the strapped to bomb situation, and adopt a branch that does not go there. Now THAT does make my brain hurt. Also, the idea of a conscious organism that continues to decay but never dies, has some compelling analogues. Perhaps, this process would lead to me becoming a sort of devolved form of life, eventually turning into some kind of organic soup, keeping only the most rudimentary apparatus allowing for consciousness. Would I ever be allowed to become unconscious and die in this way? Or would I be like a light ray that becomes so weak that its wave length is light years long, and it can no longer interact with matter, but it still perseveres, crossing the universe with its ghostly message? Myles325a 06:13, 17 August 2007 (UTC)

User:Myles325a deleted the question I asked on this thread. I was truly curious about it. Why the deletion? Pfly 07:31, 17 August 2007 (UTC)

Looks like it was an editing accident - I've added your question back into the question stream right at the bottom. SteveBaker 15:06, 17 August 2007 (UTC)

In answer to the question of "NO chance of survival in ANY scenario whatsoever, like surviving a nuclear blast while being strapped to the bomb" - I sense that you lack the true sense of what it means for there to be an INFINITY of possible parallel universes in which EVERY outcome is played out an INFINITE number of times. So:

• A cosmic ray hits the bomb timer and changes a 0 to a 1 in the computer chip instructing it not to detonate.
• It detonates and by a billion-trillion-quadrillion to one chance caused by a microscopic flaw in the shape of the plutonium in the bomb you are flung away from the bomb and land unscathed in a tree 100 miles from ground zero with nothing more than a small scratch on your left thumb.
• You are indeed blasted into atoms - but by a googol-to-one chance, your atoms happen to land in a pile that is exactly the same as you before the explosion and you carry on living as if nothing had happened.
• The Starship Enterprise (complete with crew from the first series) forms spontaneously from an amazingly coincidental set of virtual particle/antiparticle pairs. In his surprise at suddenly forming from the nothingness of space, and concerned about the 'anti-particle' version of himself - Spock accidentally sits on the transporter controls 2 seconds before the bomb goes off and by virtue of the incorrect settings of the Hisenberg compensator, it winds up being transported into the transporter bay - the bomb goes off and returns all of the particles of the Enterprise to annihilate with their anti-particles, returning space to how it was just moments before any of this happened. All that is left from the molecules of the atom bomb is a rather confused sperm whale and a bowl of petunias (who are thinking "Oh no, not again").

Yes, these things are ASTRONOMICALLY unlikely - but they aren't INFINITELY unlikely - they are so unlikely that the odds are incalculably tiny - but at the subatomic level, everything is random - so everything you could possibly imagine CAN happen...and indeed MUST happen. If it can happen at all - it'll happen an infinite number of times (in some of them, it's Scotty that sits on the transporter controls).

So yes - if we believe this theory then you can (and will) survive the worst death you can come up with. SteveBaker 14:30, 17 August 2007 (UTC)

In the search of balance I'd like to add that these statements are only defendable if the many worlds interpretation can be taken as fact, which is an audacious and somewhat contentious thing to do, seeing as there are many other interpretations. So though it may be an educated opinion, supported by the proponents of its underlying theorem, we must not deviate from the fact that it is just that, an opinion. Not fact. ΦΙΛ Κ 18:46, 17 August 2007 (UTC)

Yes, absolutely. There are at least a couple of other interpretations that don't entail parallel universes. Nobody yet knows which is true. You also have to be a proponent of the strong anthropic principle - which is just as contentious. I doubt that one in three experts in quantum theory would support many-worlds - and probably less than one in ten scientists are comfortable with the strong anthropic principle - so perhaps only a few percent of experts in the field would remotely consider quantum immortality to be possible - and even then, the idea that you can be arbitarily close to death and still be considered to be an active observer may well mean that even if both principles turn out to be true, the quantum immortality thing may be nothing. I sure hope so - because I can't imagine a worse way to exist. SteveBaker 19:33, 17 August 2007 (UTC)

Touche. But also if believing that we see the universe the way it is because if it were different we would not be here to observe it is being anthropic, then yes I am. But with many worlds, you do have to consider that even if all possible paths are considered not all outcomes are possible. ΦΙΛ Κ 23:31, 17 August 2007 (UTC)

Closed Time-Like Loops

Hypothesized to exist philosphically/physically when the big bang(big crunch) creates(destroys) time due to the nature of anything leading up to the big bang not affecting our current universe, and in the negative radius of of a spinning black hole's circular singularity, closed time-like loops go-on and reapeat to infinity. If relative time, or true time, were to play back a "recorded version" of a seemingly infinite loop, one would find a beginning other than the one seen repeated infinitely in the loop. As in the case of the black hole, it would be the infalling energy or space in our real universe outside the horizon. My question is, in the case of the universe, what would I find? Borahborah 10:15, 16 August 2007 (UTC)

Since this is all hypothetical there may be no particular answer. However you may be able to use topology to describe possibilities. Can I rephrase your question as whether linear time and loop time could exist in the same universe? One possibility I can think of is a wormhole that goes back into the past. A time line could travel through the wormhole and back to it again. This may repeat forever. Otherwise perhaps the whole universe is in a time loop and the big crunch returns as a big bang. Graeme Bartlett 02:08, 18 August 2007 (UTC)

Iron pentacarbonyl

What technique is used to detect trace level of Iron pentacarbonyl in gases ? 71.199.170.8 10:53, 16 August 2007 (UTC)

Mass spectroscopy might be a easy one.--Stone 11:01, 16 August 2007 (UTC)

FT-IR is another.87.102.66.173 12:05, 16 August 2007 (UTC)

Depends how trace is "trace", what else is in the gas, whether it needs to be on-line or can be an off-line sample, whether it can be destructive testing, etc. Googling for "iron pentacarbonyl" detection gives some good refs for some applications. DMacks 15:06, 16 August 2007 (UTC)

cities

which is the worlds most technologically advanced city —Preceding unsigned comment added by 41.207.68.129 (talk • contribs) 12:05, 16 August 2007

Tehachapi, California.

(That's a wrong answer, btw, but it's not much more wrong than any of the "right" answers you're likely to get. The question is impossible, of course; there's no one right answer. We can't even say what the world's longest or tallest bridge is; how can we possibly determine the "most technologically advanced" city?

What do people think they're looking for when they ask these questions? There's an implicit notion that any attribute of any entity can be reduced to a simple, objective, linear scale. It's at best a goofball, and at worst a dangerously misguided notion -- why is it so prevalent?)

—Steve Summit (talk) 12:30, 16 August 2007 (UTC)

It's prevalent because most mainstream educational systems are very effective at destroying the capacity for original thought, and insist on a single "right" answer for any question. DuncanHill 12:43, 16 August 2007 (UTC)

Is this a reference desk or a pie throwing contest? Bendž|Ť 14:56, 16 August 2007 (UTC)

...KERSPLAT!!! - gotcha! Hehehehehe! SteveBaker 16:37, 16 August 2007 (UTC)

There are things for which a simple one-dimensional scale is possible - but this isn't one of them. It's not even clear what the question is. For example, are we asking which city produces the most advanced technology - or the city that uses most? Are we looking for the most widespread use of technology (measured, say by the city with the highest cellphone usage) - or the single most advanced single use (eg: Which city has the most advanced Particle accelerator)? It's really not a very answerable question. SteveBaker 16:37, 16 August 2007 (UTC)

While I agree with the above, about never being able to answer the question fully, since we don't know what that even means [9], I'm going to have a go at offering some examples.

• According to the BBC, Tallinn appears to be among the most technologically advanced cities in Europe. [10], While Birmingham ranked top for "eGovernment" [11]
• Popular Science "weighed dozens of variables, from the number of homes with wireless internet to the number of robotic surgeries performed at local hospitals, to rank U.S. cities by tech quotient". Their overall ranking was [12]:

1. Minneapolis-St. Paul
2. Atlanta
3. Washington D.C.
4. Boston/Cambridge
5. San Diego

• Some magazine list Shanghai or Tokyo as the most advanced, wile others cite purpose built "cities" (although most of them are really towns or suburbs, certainly much smaller than a regular city) like New Songdo City and Cyberjaya. Rockpocket 18:39, 16 August 2007 (UTC)

Redmond, it has Microsoft. :-) --S.dedalus 22:27, 16 August 2007 (UTC)

While you're at it guys, which is the most beautiful city, and which city is the happiest? Capuchin 08:05, 17 August 2007 (UTC)

If you mean natural beauty, then Rio de Janeiro and Cape Town are often mentioned. No idea about the happiest city. Rockpocket 18:04, 17 August 2007 (UTC)

As for the most technologically advanced city, that would most likely be in a rich country. And it would probably be a new city (as a city) because old infrastructure can hold back new developments. As for the Internet connectivity, the Netherlands is one of the top ranking countries. In the Netherlands, Eindhoven is a very new city. And it's the home of Philips, a rather innovative automobile industry, a University of Technology and ASML, one of just three companies in the world that make the machines that make the machines on which our society runs. Of course there's no definite answer to the question, but Eindhoven would probably be fairly high on the list. As for beauty, well, it's butt-ugly. I know this because I have studied there for four years. As for happiness, the Netherlands usually scores rather high on international polls in which people are asked how happy they are. Not that I put a lot of faith in those polls, but it should help that the Netherlands is one of the richest countries in the world (per capita) in exchange for a normal working week of just over 30 hours, combined with a very low income inequality, insuring everyone can enjoy the wealth. DirkvdM 07:58, 19 August 2007 (UTC)

Dream question

I remember a little bit of a dream I had last night in which I was going to say the name of a running back who plays for the Chiefs (I would explain why, but it would make even less sense) and another guy in the dream said "Priest Holmes!" before I could think of his name. And that's who it was! I kind of assume that my thoughts in dreams are at a more conscious level than whatever it is that is making all of the other stuff (other people, places, events, etc.). Is that a good assumption to make? If so, how did my subconscious know before I did? Are there Wikipedia articles that address the difference between "self" and "other" in dreams? Recury 13:39, 16 August 2007 (UTC)

I think that's a really good question. Dream_interpretation says that Jung considered others in dreams to represent parts of the self. But I'm not aware of any discussion about how the brain seems able to simulate multiple others with enough complexity as to seem conscious and with access to memory, all without these others sharing the consciousness of the dreaming person. --Allen 14:47, 16 August 2007 (UTC)

Unless of course Recury knows the other guy in real life, which means his brain would not have needed to create too much SGGH ^speak! 19:44, 16 August 2007 (UTC)

Inhibited self control is a common dream issue. It is usually an inability to walk. It can also be an inability to do things such as open a door or start a car. Similarly, it can be an inability to speak. When this occurs, it is normal for other entities in the dream to continue as normal. Therefore, you had an inability to think of a name while another entity in the dream could think of the name normally. All in all, it is a normal dream. As for what it means, that is debatable. I've usually heard it interpreted as a lack of self esteem. -- Kainaw^(what?) 19:12, 16 August 2007 (UTC)

No, no, no. This was a very small part of the dream and I'm quite sure it "meant" nothing. We were even having the conversation while we were doing something else (travelling somewhere as part of a large group). I really don't remember much else but there were a lot of other things that happened before it. To answer your question SGGH, we were friends in the dream, but he wasn't anyone I knew in real life. It wasn't as if I was having serious trouble remember the name either, he just kind of interrupted me while I was pausing or saying "um" to interject. But I'm not really interested in the meaning or content of the dream as such, just how that specific part of it was created. Recury 02:11, 17 August 2007 (UTC)

Dreams are all about the subconscious, it controls everything in your dream. Unless of course you take over. Your subconscious knew because it's the part of the mind that's doing *everything*. Anyway, look into Lucid Dreaming, it will explain a lot about how dreams works, and it's the most fun you can have without being imprisoned. Plus, you can show your subconscious who's boss-- there's not much you can't control in lucid dreams. Although the "people" there are odd... --Lucid 19:46, 17 August 2007 (UTC)

Nero mammoths

These beasts appear in the Prehistory section of two articles, History of Kansas and History of Arizona, and seem to have sprung from the same source. Would anyone have any idea what "Nero" refers to? (The answer may have nothing to do with any kind of science, in which case I apologize for the intrusion on this reference desk.) - Mu 15:52, 16 August 2007 (UTC)

No idea; the only google links are Wikipedia. Probably should be removed. Geologyguy 16:06, 16 August 2007 (UTC)

The phrase was added to the Kansas article on September 27, 2005 by User:Reddi, who is a major contributor. I will remove the instances in both articles, and leave a note for Reddi. Flyguy649 ^talk _contribs 16:20, 16 August 2007 (UTC)

"Sashimi Grade" fish, and parasites and other nasties

About once a week I go past a prominent fish-shop and ask them if they have any "Sashimi Grade" salmon or tuna- and when they say they have stock, I order, and they go into the back and come back with my order. However, what is totally killing the fantastic sashimi experience, is my paranoia over parasites and other nasties.
Some questions not addressed in the sashimi article:

• If something is "sashimi grade" fish, does that sort of guarantee that it's been frozen, or just that the fish is of a high quality? Or does it only refer to the "cut" of fish - the part of the fillet with the most oil (as one fishmonger I spoke to claimed "It's just about the cut")?
• After buying "sashimi grade" fish, are you still expeced to thoroughly check the meet for any sign of parasites?
• Is there some resource that I can use to educate myself on all the possible little things to look out for?
  

Any knowledgeable answers would be appreciated.
Rfwoolf 17:36, 16 August 2007 (UTC)

According to this, it looks as if there is no governmentally enforced standard involving "sushi" or "sashimi grade" fish in the U.S.
Here is some advice from the FDA for selecting fresh, safe seafood, and here is an overview of the FDA's seafood regulatory program.
If you want a definitive answer, you could cal 1-888-SEAFOOD (not a joke, btw).
Mrdeath5493 05:50, 17 August 2007 (UTC)

Wouldn't uncooked fish, even if previously frozen, be capable of introducing parasites into the body of the person consuming it? Edison 15:47, 17 August 2007 (UTC)

Freezing an organism will kill it. Some organisms have freezing points significantly lower than water, but to my knowledge, these are only organisms that hibernate at temperatures below freezing. Freezing the fish will kill anything in it just as effectively as boiling it. — Daniel 04:18, 18 August 2007 (UTC)

But freezing fish changes the texture. So high-end sushi and sashimi is prepared from never-frozen fish. There was a huge row about this here in 2004. The provicial government (Ontario, if you care) ruled that all fish had to be frozen prior to use in sushi and sashimi. There was a huge outcry, and it was recinded. There's more info about freezing fish in this PDF. I guess part of the training for sushi chefs is recognizing whether the fish has parasites. Flyguy649 ^talk _contribs 04:31, 18 August 2007 (UTC)

Banana skins

I would like to know why banana's are typically eaten without their skins, as I prefer to eat them whole, as I don't like the mushiness/softness of them without the hard skin to contain them. Could anybody tell me why the skins are not eaten? Thanks 81.110.75.212 17:48, 16 August 2007 (UTC)Steven

This may vary with both the eater and the variety of banana - I personally have tasted banana skin and found it bitter. DuncanHill 17:53, 16 August 2007 (UTC)

Thanks, so it's just a matter of taste rather than there being anything poisonous to humans in them?81.110.75.212 20:44, 16 August 2007 (UTC)Steven

Just make sure to wash them thoroughly. Since the skin isn't generally eaten, I suspect handlers and vendors are less concerned about cleaning the fruit than might otherwise be the case. But then, washing fruit before eating is always a good idea :) GeeJo ^(t)⁄_(c) • 22:15, 16 August 2007 (UTC)

I seem to remember that in any pictures I've seen of other great apes, such as chimpanzees and gorillas, eating bananas they usually peel them as well. As far as I know there's nothing dangerous about eating the skins per se. Most people I think would find them pretty bitter as Duncan said, and also very tough and unappealing in general texture and mouth-feel. But maybe it's just a matter of taste. --jjron 09:57, 17 August 2007 (UTC)

If banana skins were poisonous, believe me, we'd know about it.

• The only part of a commonly-eaten plant that's truly poisonous is the leaf of the rhubarb. Usually, when you buy rhubarb, the leaves have all been carefully stripped off, to protect you in case you don't know to.
• The only parts of commonly-eaten plants that are microscopically poisonous are the seeds of apples, peaches, and a few other stone fruit; these all contain trace (and unharmful) quantities of cyanide.
• A plant that was once thought to be poisonous, but is commonly eaten today, is the potato, which is related to deadly nightshade, although not, as we now know, closely enough to be poisonous itself.

As you can see, this is a very short list. No bananas in sight. —Steve Summit (talk) 13:19, 17 August 2007 (UTC)

Our article on the Tomato says that the leaves and stems of that plant are poisonous - so it's not just the rhubarb. Whilst the potato isn't poisonous as such, the 'eyes' in old potatoes are a risk to unborn babies - pregnant women must not eat potatoes that have started to sprout like that. Also, uncooked potatoes - whilst not poisonous - will make you quite sick because of the way humans digest starches. Chimpanzees and Orangutans always eat the entire banana (unless they've been trained not to) - they are sufficiently closely related to us that we can deduce that we can eat the banana skins too. SteveBaker 14:08, 17 August 2007 (UTC)

Cashew nuts are also poisonous but fairly harmless once cooked. Tapioca (cassava) is also poisonious altho again fairly harmless if processed properly. Bamboo shoots also have cynageous compounds altho generally not in sufficient concentrations to be harmful [13]. Also see cyanide. As for Oxalic acid, it's also present in star fruit and other commonly consumed plant parts. Nil Einne 14:30, 18 August 2007 (UTC)

This calls to mind Nerval's poem Delfica

Reconnais-tu le Temple au péristyle immense,

Et les citrons amers où s'imprimaient tes dents,

Et la grotte, fatale aux hôtes imprudents,

Où du dragon vaincu dort l'antique semence?...

(Among other things, he remembers his girlfriend biting into bitter lemons) Xn4 00:47, 19 August 2007 (UTC)

cytochrome c measurement

Hi, my question is related with the measurement of cytochrome c from canine blood. So far we have tried using HPLC but because of the high amount of proteins on it the life time of the columns gets short. Besides the results are variables and so the standar peaks. ELISA would be a good idea but seemenly there are some proteins binded to cytochrome c and its use could not be meaningful. according with some papers we should have to dilute the samples and at the same time dilute the cytochrome c. What do you advice me? Thank you very much,

Pedro Vargas —Preceding unsigned comment added by Pitvarpin (talk • contribs)

HPLC of unmodified blood will probably not produce any reliable results due to the rapid deterioration of the column. This would also be quit expensive. When a column changes that much from calibration to testing, the results will be questioned. I can't be too specific here, but the general strategy would be to get blood with the least amount of extra stuff in it as well as cytochrome c. Can you add anything to the blood that will make unwanted compounds precipitate out? How would a centrifuge affect unmodified blood? Could you centrifuge the blood, extract only the layer where you would expect to find Cyto-c, lyse the remainder, and then run the HPLC (hoping to improve column life)?
There are companies that do stuff like this and patent the column so they can sell it;they usually provide some sort of standardized method for whatever you want to do, but it necessitates the use of their column.
Most of what I said was very speculative: Mrdeath5493 06:08, 17 August 2007 (UTC)

troubleshooting

i would like to now hints on how to troubleshoot an electrical line.≠41.219.216.183 21:17, 16 August 2007 (UTC)

Very carefully. You should probably not troubleshoot an electric power line if you are not a trained electrician because high voltages and currents in electric power lines can kill you. Call an electrician. If you are seeking a long-term solution, you might consider one of the various engineering disciplines or a vocational training as an electrical technician. Nimur 21:34, 16 August 2007 (UTC)

You may wish to document carefully what is the problem - eg no power form a power point - which ones, circuit breaker popping, lights too dim, overheating in part of the line. You can unplug all your appliances from power points and then plug in one by one to see when the problem appears. (Divide and conquer algorithm) What kind of electrical line are you talking about? Graeme Bartlett 23:37, 16 August 2007 (UTC)

Most stores (Walmart, KMart, Target, Home Depot, Lowes...) sell a device that looks like a pen. When AC current is near the tip, it will flash and beep. This is handy (and relatively safe) for non-technicians to use. Buy one (they are not expensive). Put it near an outlet that has power. Notice that it beeps. Now, go to an outlet that you don't think works. If it beeps, the outlet is working - it is some other problem (perhaps the outlet is wired wrong). If it doesn't beep, go to the switch for the outlet. Does it beep? If so, the switch is most likely bad. If not, follow the line to the next part - usually the breaker box. Note that this can also be used to see if there are power lines behind the wall. You can follow a live line by tracing the beep along the wall. Since you never actually touch a wire, it isn't too dangerous. -- Kainaw^(what?) 23:47, 16 August 2007 (UTC)

There are different ways for different kinds of electrical lines. What is appropriate for a 15 amp circuit in the walls of your house would not be appropriate for a 12000 volt underground cable or a 345,000 volt overhead line or a 120 volt DC control cable in a piece of equipment. Edison 15:45, 17 August 2007 (UTC)

Birth of a seagull

Does anyone know where I can find a video of a seagull egg hatching? --84.65.110.20 22:36, 16 August 2007 (UTC)

Youtube here [14] DuncanHill 22:45, 16 August 2007 (UTC)

Man, I was looking on YouTube for more gull hatching vids and I found this one. That's just pure evil. Why the hell would someone do that - *and* be stupid enough to post it online? Does anyone live in Gibraltar here? The person who made that video should be reported to the local police. F-ing dirtbags. --Kurt Shaped Box 23:19, 16 August 2007 (UTC)

I too found that one. I reported it to Youtube as inappropriate. Was really rather vile. DuncanHill 23:23, 16 August 2007 (UTC)

I'm honestly shocked. I mean, what was the point of that? Those kids belong in a detention home. If those were British kids, I'd be forwarding that video to the authorities - people have gone to jail here for doing that sort of thing. --Kurt Shaped Box 23:29, 16 August 2007 (UTC)

They appear to be breaking Section 3 of the Nature Protection Act 1991. [15] DuncanHill 00:45, 17 August 2007 (UTC)

And the Royal Gibraltar Police have now been notified. DuncanHill 00:54, 17 August 2007 (UTC)

Damn right. See my post on your talk... --Kurt Shaped Box 01:03, 17 August 2007 (UTC)

That is completely and utterly vile. Those brats are lucky that I wasn't there when they were torturing that chick. If I'd caught them at it, they'd be drinking their food through a straw and wouldn't be having kids of their own - ever. I hope the Gibraltar cops throw the book at them (they still birch criminals in Gibraltar, don't they?). Beneath contempt. Takes a real big, tough man to take on a baby bird still in the egg, huh? --84.66.252.78 18:37, 17 August 2007 (UTC)

August 17

Dangerous love

Is there any evidence of a link between sexual/romantic activity and immanent physical danger in humans? Judging from books like “For Whom the Bell Tolls” there is a positive link. Are there any real world examples of, for instance, a surge in marriages during The blitz, or a surge in sexual activity in people suffering from the early stages of terminal diseases? Last question, does Wikipedia have an article on this, and if not what could it be called? Thanks! --S.dedalus 00:35, 17 August 2007 (UTC)

Anthony Burgess touches on this idea repeatedly in many of his novels, but I don't know if there is a formal term or even if there has been any scholarly research. DuncanHill 01:53, 17 August 2007 (UTC)

"A British novelist, critic, composer. . . librettist, poet, pianist, playwright, screenwriter, journalist, essayist, travel writer, broadcaster, translator, linguist and educationalist." Wow, quite a guy! --S.dedalus 02:21, 17 August 2007 (UTC)

I am something of a fan, and if as I seem to recall (your username is something of a giveaway) you are a Joyce fan, you may well find him of interest. He wrote a book (Here Comes Everybody - a Guide to Joyce) which I find very helpful, and clearly was a great admirer of Joyce's use of language. I think he even included Joyce as a character in a few stories, which I'll try to look out for you. DuncanHill 02:32, 17 August 2007 (UTC)

Of course we have the Post-World War II baby boom - caused by a huge increase in sexual activity immediately following the end of WWII - but that was from a release of imminent danger rather than the onset of it. SteveBaker 15:00, 17 August 2007 (UTC)

More fiction, I'm afraid, but the one lesson I learned from a childhood of watching horror movies is that if teenagers have sex in the woods, they're going to be subject to a bit of the old ultraviolence. --Sean 15:06, 17 August 2007 (UTC)

Well, it makes sense to me, at least from a male genetic perspective, to try to scatter your genes as widely as possible before your death. I wouldn’t think the same logic would hold true for a female though. This seems to be one of these phenomena that is often depicted in fiction and take for granted to be true. --S.dedalus 21:36, 17 August 2007 (UTC)

The original question was about "immanent physical danger". I think we can all agree that sexual activity comports inherent physical danger, though the danger can be reduced with prudent measures. This is not the most usual usage of immanent, a term that tends to be seen largely in theological contexts, but it does seem to fit the dictionary definition, anyway. --Trovatore 21:55, 17 August 2007 (UTC)

That’s true. However, I was thinking more in terms of an evolutionary or psychological phenomenon, which would be unlikely to be influenced by such considerations. So no one knows of any research that has been done on this? --S.dedalus 22:55, 17 August 2007 (UTC)

I think you missed my (not all that) subtle point. --Trovatore 22:57, 17 August 2007 (UTC)

That’s always a possibility. My understanding was that you are pointing out the danger inherent in sex. However, this would create a circular logic problem if we assume the “Dangerous love” phenomenon is true. --S.dedalus 23:52, 17 August 2007 (UTC)

What I was pointing out was that "immanent" is a perfectly fine word, but I do not think it means what you think it means. --Trovatore 00:03, 18 August 2007 (UTC)

Oh, ha ha, imminent then if you prefer. You can probably guess that spelling is not my strong suit. --S.dedalus 00:42, 18 August 2007 (UTC)

There's also the rickety bridge experiment. --136.186.1.191 07:31, 22 August 2007 (UTC)

Shape of the eye

I was told that prolonged wearing of glasses would cause the eye to bulge due to the eye's adaptation to the peripherial lenses. However, there is this thing I don't get. Glasses are supposed to fit your degree of near/far-sightedness, and should not require your eyes to deform to achieve focus. What's more is that (well, this I base on a speculation) if the eyes deform due to their seeking for the focus, people who are near/far-sighted and who don't wear glasses should have more or less the same problem shouldn't they?

Uh... I think whoever told you that is probably wrong. Sometimes people's poor vision is caused by bulging eyes, but I'm pretty sure that glasses themselves don't make the eyes bulge. --24.147.86.187 01:45, 17 August 2007 (UTC)

Assuming you've got the right prescription..Wearing the wrong glasses might have that effect.87.102.14.51 08:24, 17 August 2007 (UTC)

Sounds like an urban myth to me. Ask for some references to reputable sources. --jjron 09:50, 17 August 2007 (UTC)

I totally agree it's an urban myth. There is very strong evidence that, with potential side effects, contact lenses can reshape the cornea via Orthokeratology but if it were true that spectacles that could reshape the eye wouldn't we be using them to correct vision rather than permanent specs, contact lenses and laser surgery? Maybe there's more truth to the notion that wearing glasses weakens the cornea's ability to regenerate, any evidence on that? --82.12.235.69 20:29, 17 August 2007 (UTC)

Chemistry and Botany

Dear Wikipedia, —Preceding unsigned comment added by 61.95.55.2 (talk • contribs)

To the questioner about Chemistry & Botany who started with such charming good manners - Your question seems to have got lost - please try posting it again, thank you. DuncanHill 02:12, 17 August 2007 (UTC)

The article on Urticaria regarding treatement and cause is incomplete

I'm a victim of Utricia myself and it is a rashes from hell...very very extremely torturous.

I developed many sympthom similar to the cold/hot and other type of Urticaria. However later the actual caseu of my chronic Urticaria is actually identify by a doctor. It is due to parasite in my stomach from eating raw fish. My suffering duration was 1 year but was treated within 1 day by taking any parasite killing pill.

Hence i really hope my piece of information will be publish to share to end suffering of many in same shoes

Thanks for your information, but:

1. This appears to be a personal piece of information, not a question - the Reference Desk is for asking questions.
2. WIKIPEDIA DOES NOT GIVE MEDICAL ADVICE.
3. If you have referenced information from reputable sources that would support this treatment you are able to add it to the appropriate article yourself and cite the references. As is, it would be termed anecdotal evidence and would also be considered original research. So, while I'm glad you have recovered from your illness, for these reasons this would not be appropriate to be added to the article. --jjron 09:44, 17 August 2007 (UTC)

Dear 61.95.55.2, can you find a published source that describes what you experienced? In this case you may be able to update the article with your summary of the paper or book. Graeme Bartlett 02:11, 18 August 2007 (UTC)

Stroboscopic Effect again

Sorry that I couldn't get the track of discussion that day..As you have mentioned clearly that the effect is called stroboscopic effect or temporal aliasing (as steve baker said), which is only due to some tv replays or movies and also couldbe due to reflection, but I belive it's not true so...I have noticed this effect simply when the ceiling fan(for eg) rotating at high speed or a DC servo motor(with wings) speeding up\down also creates this effect in our eyes...How is this?..This is a real vision and our eye captures lively the action.Though i didn't see it under sunlight, but sure inside my physics lab light.Also what's the big difference between the daytime and nighttime's role in this?..You can give a try by looking at your cooling or exhaust fan...Thanks

Your lab light is strobing, at night, certain street lights (such as those in tunnels) are also strobing. This produces the effect. You should be able to move yoru finger left to right (fairly quickly) infront of your light and see several distinct impressions of the finger on your vision as you move it. Each of those impressions is due to a single strobe. If you are in natural sunlight, you don't see that effect, it will look like more of a blur. This should confirm that your light is strobing.

Please sign your posts with four tildes (~) Capuchin 10:18, 17 August 2007 (UTC)

OK - let's try again with a simpler explanation. Let's suppose your ceiling fan has four blades - set 90 degrees apart - and let's suppose you live here in the USA where the mains power is 60Hz - the voltage provided by the wall socket goes up and down 60 times a second. The brightness of your room lights depend on that voltage so they get brighter and dimmer 60 times a second. (Someone is going to complain that this isn't exactly true - but it's true enough for this simple explanation so we're going to ignore them!)

In a sense, the room goes dark and you can't see a thing - then 1/60th second later, the lights come on and you can see - then 1/60th second later it goes dark again - 1/60th second later and they are back on again. This is far too fast for you to consciously notice it - but your eyes are still seeing it.

Now - as for the fan: If the fan has four blades which look exactly alike, then it looks no different when it's rotated zero degrees than it does when it's rotated 90 degrees, 180 degrees or 270 degrees. It has rotational symmetry.

Alright - so let's suppose the fan is spinning at exactly 15 revolutions per second. That means it's turning 15x360 degrees per second - 5400 degrees per second - which means that it turns 5400/60 degrees between the time the room lights go on, then off, then back on again. So (by an amazing coincidence brought about by my choice of numbers!) that's 90 degrees of fan rotation between the individual 60Hz flashes of light. But remember that the fan looks exactly the same when it's rotated by 90 degrees - so whenever the light is on, you always see the fan with the blades in the exact same position. It looks to you like it's not moving at all! This is the crux of the thing - when the fan blades rotate by exactly 90 degrees between light flashes - it looks like it's not moving at all because the only time you have enough light to see them by - they always look like they are pointing in the exact same direction.

Now - in sunlight, there is no 1/60th second flashing - the sun doesn't turn on and off - you get continuous light. So now, your eyes can see the blades of the fan all the time and nothing special happens - you just see a lot of blurry fan blades. The 'strobe' effect doesn't happen because there is nothing flashing on and off to block your vision of the times when the fan has rotated 10 degrees or 11 degrees or 12 degrees or whatever.

When you film the same fan blades using a television camera (which just happens to take 60 pictures per second) - you get the exact same phenomena - the fan blades move exactly 90 degrees between each TV picture - and they look as if they have stopped moving.

Now - it's unlikely (well, maybe not...) that the fan is really going to rotate at exactly 15 revolutions per second. Suppose it only rotates at 14.9 revolutions per second? Well now, instead of 5400 degrees per second (or 90 degrees per flash of the room lights), it only rotates 5364 degrees per second - so between each flash of light, it turned 5364/60 degrees - or about 89 degrees between each flash of light. Well, now - what do you see in this situation? You don't see the fan blades in exactly the same position each flash - the fan only rotated 89 degrees between flashes. But if the fan looks exactly the same when rotated by 90 degrees - there are two possible explanations for what you are seeing - either the fan is spinning at 89 degrees per flash - OR it's spinning backwards at 1 degree per light flash. Sadly, our stupid brains get it wrong and guess that it's spinning very slowly backwards at 1 degree per light flash or 60 degrees per second. This is why, as the fan spins slowly faster and faster, it seems to go faster and faster until it's turning just a little bit less than 45 degrees per flash - but when it's spinning at 46 degrees per flash, your brain starts insisting that it's going backwards at 44 degrees instead. So you get that weird situation, where the fan seems to speed up - then abruptly reverse direction, slow down and eventually stop - then start going forwards again.

The effect works with anything that has some kind of symmetry that's moving just right.

There are lots of other complications - but that's the simplest way I can come up with to explain it. If you don't understand it now - re-read what I just wrote! SteveBaker 13:28, 17 August 2007 (UTC)

Once again: there are 120 flashes per second, not 60. And the phases of light and darkness are shorter yet, since you have light and darkness in each 1/120 second period. So instead of 1/60 second, you need to say something like "1/240 second later it's dark, 1/240 second later it's light again". Adjust the other details accordingly; Steve describes the general idea correctly. --Anon, August 17, edited 22:00 (UTC).

And read the article :) Capuchin 13:40, 17 August 2007 (UTC)

Wow that was really an useful info explained in a clear way...Thanks you two...You really have a good knowledge on science...great

You might be interested to know how come I know so much about this. I work in computer graphics (I used to design flight simulators - now I write computer games) - and we have the same problem with wheels of cars and blades of helicopter rotors and such. We call it 'temporal aliasing'. When a car with wheels that have four spokes are driving along in a computer game, they are drawn (maybe) 60 times a second - so, once again, we see the peculiar reversing of direction and so on. This happens when the wheel rotates at one half of the angle between the spokes or faster. So for a wheel with only four spokes, the wheel can rotate up to 44.999 degrees every 1/60th second and it looks great - but the moment it hits 45 degrees per 1/60th second, we're screwed. Unfortunately, real car wheels often have more than four spokes - maybe a LOT more than four. If it has 8 spokes then it'll start to misbehave at 22.5 degrees per 1/60th second. Well, that's about 4 revolutions per second - which for a typical 24" wheel happens at a mere 17mph! Since this looks particularly weird in the 'perfect' world of computer graphics, it's necessary to blur the wheel into a more or less uniform circular 'smoosh' well before the car gets up to 17mph! Anyway - to make wheels and helicopter rotors and other things look good, it's essential to understand the horrible details of temporal aliasing. SteveBaker 03:47, 19 August 2007 (UTC)

Vertical polarization

I do know that I must've looked googling for this doubts but I don't know how to pick this idea very keenly there..So I'm posting here friends...Can anybody just tell me what do they mean by "vertical Polarization" in satellite communication?..I have seen this in the TV screen of the receiver displaying satellite number and downlink freq and so along with this...Thanks in advance

Antenna_(radio)#Polarization may be the thing to read - (I can't say I understood it myself so please do not blaim me if info is wrong)87.102.14.51 10:56, 17 August 2007 (UTC)

Essentially, you can think of radio waves as vibrating "in just one plane". That plane can exist at any angle, but the cool part is that if you have one radio wave vibrating in one plane (that's oriented, say, vertically, so vertically polarized), and another radio wave that's vibrating in a plane that's rotated 90 degrees (in other words, is at a right angle to the other plane, so say, oriented horizontally, so horizontally polarized), a radio antenna can sort these two signals out. The angle of the signal (and the vibration plane) is referred to as the signal's polarization. So any given frequency can be used to carry two different signals: one polarized vertically and one polarized horizontally. So your satellite company only needs half as many channels as they might otherwise need and they need to tell you that you want to receive, say, the vertically-polarized signal that's on channel 16 (as compared to the horizontally-polarized signal that's also on channel 16).

This technique is commonly used for microwave transmissions but it's not universal. For example, FM broadcast radio stations commonly broadcast with circular polarization or elliptical polarization; these are ways to send a signal that has both sorts of polarization simultaneously. This lets their signal be received both by dipole antennas such as are commonly used at home and by whip antennas as are commonly used by cars and portable radios.

Atlant 12:35, 17 August 2007 (UTC)

Simpler (but longer) explanation: Radio waves (and also light, microwaves, etc) can vibrate in different directions - up-and-down, side-to-side, diagonally, or all directions at once - this is called the 'polarisation' of the wave. If you have a radio antenna that's set up to receive up-and-down vibrations ('vertical polarisation') - it won't pick up side-to-side vibrations ('horizontal polarisation') - and vice versa. This is a rather convenient thing for satellites because it allows them to send more than one channel out on the same frequency by sending one out with vertical polarisation and a different channel with horizontal polarization. So-called 'circular polarisation' is what you get when the signal vibrates in every possible direction at once - and these signals can be picked up by antennas set up for horizontal polarisation and those set up for vertical polarisation. You can learn more about how this stuff works by playing with the polarisation of light using polaroid sunglasses. Natural sunlight has circular polarisation - but when the light bounces off of a horizontal surface, the reflected light comes out with only horizontal polarisation. Polaroid sunglasses are set up to only allow vertically polarised light to come through - so they block horizontally polarised glare - whilst allowing ordinary circularly polarised sunlight to pass through. If you take two pairs of sunglasses and rotate the lens of one pair at right angles to the other, you notice that the two lenses block almost all of the light. That's because the first lens only allowed vertically polarised light through - and the second only horizontal - so none of the light that made it through the first lens could pass through through the second one (well, more or less - these lenses aren't 100% perfect). Similarly, if you wear a pair of polaroids and look at the reflection of sunlight from (say) a shiney car - you can change the brightness of the reflection by tipping your head to one side so that the glasses now allow horizontal polarised light through and block the vertically polarised light instead. SteveBaker 12:57, 17 August 2007 (UTC)

It's true that sunlight "vibrates" in "all directions at once", but it is not circularly polarized, which visits the directions in a predictable sequence, but rather unpolarized, which visits them randomly. (That said, what you say about polarized sunglasses is true.) For a narrow (in terms of solid angle) pencil beam of light, I believe that sunlight is spatially coherent, but that's not the same thing either. --Tardis 16:35, 17 August 2007 (UTC)

Any given geosynchronous satellite has several radio transmitters (transponders, actually) and several antennas. At any particular frequency on any particular antenna, the satellite can transmit on two polarizatons simultaneously. Most Ku-band transponders use linear polarizatoin (H and V) (Some C-band transponders use circular polarization. Circular is harder to understand but easier in some ways to implement.) One interesting thing aboutlinear polarization: "H" and "L" are relative to the earth's axis. This means that an antenna on the equator looking at a satellite on its horizon will be "turned on its side" relative to an identical antenna that is due north of a satellite on its horizon.(this would be sited above the arctic circle.) A satellite in the middle latitudes (e.g., in Kansas) and looking at a satellite that is not due south must be tilted somewhere in bewteen. -Arch dude 13:47, 17 August 2007 (UTC)

Adherence

I was looking for some information about the non-stick frying pans and why the geckos cannot stick to teflon, but I did't find a general article about the adherence (physics), nor about the sucking pads. How does it work? Can some body give me an explanation? Thanks in advance. --Micru 11:52, 17 August 2007 (UTC)

The general topic article you're looking for is called adhesion, rather than adherence—but it doesn't specifically address the gecko pads. Here is an interesting article with lots of detail and pictures (warning: PDF). This page has a shorter, press-release treatment of the mechanism. For a detailed scientific study, see this PNAS article (free) or this Nature paper (subscription required). Some of this information is in our articles on the gecko and on setae—the tiny hairs that let them stick to surfaces. TenOfAllTrades(talk) 14:44, 17 August 2007 (UTC)

Thank you for the information, it was very clarifying and interesting! I have created a disambiguation page for adherence, before it was a bit misleading. --Micru 21:15, 17 August 2007 (UTC)

clean pharmacy

how a clean pharmacy operates? —Preceding unsigned comment added by 67.188.197.242 (talk • contribs) 08:04, 17 August 2007

Is that even a question? Is a "clean" pharmacy something other than a well-maintained pharmacy? -- JSBillings 13:49, 17 August 2007 (UTC)

Cleanly, perhaps? 147.197.230.174 13:53, 17 August 2007 (UTC)

Maybe one that only sells legal drugs, or sells drugs only in entirely legal ways (using 'clean' in the same sense as, say, with 'clean athletes' being ones not using drugs or other banned substances)? Surely though most pharmacies would be clean in that sense? --jjron 15:14, 17 August 2007 (UTC)

Hmm, this has me wondering if there are special facilities for packaging meds for people without functioning immune systems. In such a case, it would be critical to avoid any bacterial, viral, or other contamination to the meds. In normal cases, they try to keep contamination to a minimum, but it isn't likely to kill anyone if a bacterium gets in now and then. StuRat 20:38, 18 August 2007 (UTC)

Quarks in the Universe

Has anybody calculated the estimted number of Quarks in the universe?

Would this be the largest number known to Humankind?

—Preceding unsigned comment added by 165.123.243.168 (talk • contribs) 12:48, 17 August 2007

In answer to the second question, no, not even close. Not even close to being close. See our article on large numbers. —Steve Summit (talk) 12:59, 17 August 2007 (UTC)

It might be the largest number you could get by counting physical things - but we humans have no problem whatever imagining vastly larger numbers than the number of quarks. For example, Shannons number - which is 10¹²⁰ - is said to be the number of possible games of chess. That is VASTLY bigger than the number of quarks. (Observable_universe#Matter_content says that there are 10⁸⁰ atoms in the observable universe - most of those atoms are hydrogen and helium - so we're probably looking at an average of no more than 10 protons, neutrons and electrons per atom - which are each made up of three quarks - so even being very generous, 10⁸² is the most quarks we can expect to find. The number of possible games of chess is therefore 10³⁸ times more than the number of quarks in the observable universe! Other sources say that there are about a googol (10¹⁰⁰) fundamental particles in the universe - but even so - that's 100,000,000,000,000,000,000 times less than the number of possible games of chess. But even Shannons number isn't really big - there are much more complicated games than chess! The game of 'Go' has about 10³⁶⁰ possible games - so if every quark in the universe had another universe inside it and every quark in THOSE universes had another universe inside them and every quark in side THOSE ungodly number of universes had a Go board inside them - there wouldn't be enough Go boards to play every possible game. That's a BIG number! SteveBaker 13:58, 17 August 2007 (UTC)

Although it doesn't affect the order-of-magnitude calculation, electrons aren't made of quarks.147.197.230.174 14:34, 17 August 2007 (UTC)

Oops! Sorry! I got carried away with the 'fundamental particles' thing. My bad! SteveBaker 14:54, 17 August 2007 (UTC)

Depending on how you choose to define countable 'things', you could count the number of photons in the Universe. According to this site, photons (mostly the cosmic microwave background) outnumber other particles by about two billion to one. They make the number of quarks look just pathetic. :D If you want to stick to things with actual mass, the cosmic neutrino background contains roughly 200 particles per cubic centimeter; that works out to about an order of magnitude less than the number of microwave photons. TenOfAllTrades(talk) 14:26, 17 August 2007 (UTC)

It's still not enough to beat the number of games of chess - nor to come even close to the number of games of Go...and as combinatorial calculations go, those are tiny problems. The number of possible pictures you can display on a computer screen (something like 2^31457280!)- or the number of possible Wikipedia articles you could write using only grammatically correct English - those just dwarf the number of possible games of Go. Once you get into combinatorial calculations, the numbers can get just insanely vast. SteveBaker 14:54, 17 August 2007 (UTC)

SteveBaker wrote: “(something like 2^31457280!)” Hmmm… Do you mean: Wow! - 2^31457280 - that’s a large number! or do you mean: 2^31457280 x (2^31457280 - 1) x (2^31457280 - 2 x (2^31457280 - 3) x ... ? Myles325a 23:58, 21 August 2007 (UTC)

It's the "Wow!" thing - sorry. (I hate that they chose '!' for factorial - anything with a factorial in it is almost always an amazingly large number - so you want to stick an exclamation after it to express surprise - and then it gets confused with the mathematical function.) SteveBaker 05:48, 22 August 2007 (UTC)

Indeed. And if the number of Wikipedia articles you can write is still too small a number for you, just take 10^{number of Wikipedia articles you can write}. Or ten to the ten to that number. Etc. Or see Graham's number, which is "often described as the largest number that has ever been seriously used in a mathematical proof". --Steve Summit (talk) 15:14, 17 August 2007 (UTC)

If you want to see large numbers, look up Ackerman's numbers. Even Ackerman(4) is insanely larger that anything mentioned above, and Ackerman(5) is incomprehensibly larger than that, ...

Largest finite number, please. Plenty of proofs have used various notions of infinity. Algebraist 16:30, 17 August 2007 (UTC)

We've all been talking about finite numbers. All of the numbers mentioned so far are huge - but definitely finite. SteveBaker 17:26, 17 August 2007 (UTC)

Hi. One thing: the "observable universe" in not the whole universe! Not even close. Space can travel faster than light, but matter can't. The matter beyond the "horizon" formed as space expanded; the energy from expansion collapsed and formed matter as soon as the boundary got past it. If the observable universe counted as the universe, we, or the sun, or the milky way, would be at the centre of this universe. It could be, for example, that 10¹²⁰ was the number of grams in the universe. Thanks. ~AH1^(TCU) 22:27, 17 August 2007 (UTC)

Yes - of course. But by definition, we can't observe anything outside of the observable universe - so if the question relates to the entire universe then we have no answer. SteveBaker 00:35, 18 August 2007 (UTC)

Well, let’s hazard a ball-park figure. Suppose we use the Planck Constant as the unit to define our smallest times and lengths. The Planck Unit is so small you could fit more of them into an atom than you could atoms in the observable universe. The smallest time is that of a light crossing from one side to the other of a Planck Unit. Now, the largest thing we got is the diameter of the observable universe, which, let us say, is 15 billion light years across (probably less, but to be on the safe side).

Now let’s employ SteveBaker’s astonishing figure for how many possible piccies you could see on a computer screen (2^31457280) and extrapolate from there. Instead of a computer screen we have a screen with the diameter the 15 billion light years across. And our pixels are a single Planck unit in size. Our universe is three dimensional, not flat, so we must imagine rotating our 2 dimensional screen universe around an axis, one Planck Unit at a time. So now we have one flat screen universe multiplied by the number of Planck units it would take to stretch 14 billion light years. This is the 3 dimensional screen universe upgrade from the flat computer screen Steve Baker uses for his calculations. I don’t know how many colours Steve has figured for each computer pixel, probably millions. In the case of how many different configurations a Plank unit can take on, this is (another) area where I don’t really have much of an idea. But recently, in articles in the Scientific American to do with speculations on the nature of quantised theory of gravity, it was suggest that the Plank Unit can take on several geometrical orientations, so let’s give them 12 possible “shapes”.

Now, we can calculate the number of possible universes (as a still “picture”) as the number of different ways you could combine the digits of a number that is calculated as follows: A: Number of Planck Units in Sphere 14 billion light years in diameter X 12.

That is for a “still picture”. Of course, with Steve’s flat computer screen example, you could have a series of still pictures at, say, 100 a second, so it is relatively easy to calculate the number of such pictures you could display in an, say, an hour. (Films are shown at about 20 frames a second). Then you just have to calculate the number of possible combinations of those pictures, and you have a figure which tells you how many TV (computer screen) shows of one hour’s length can be made. About 99.9999(add about a million 9s) of these “shows” will just be colourful static with no forms at all. An unimaginably small fraction of them will be old episodes of Columbo, and some will show copies of William Shakespeare’s lost plays against a backdrop of dinosaurs and naked women. Similarly with our 3 dimensional big universe screen, we can turn the still picture into a moving one. Firstly, let’s figure that the universe is about 15 billion years old (to be on the safe side). The Plank unit of smallest time is, as noted above, the time it takes light to cross a Plank Unit of space. How many of these Plank “seconds” are there in 15 billion years. Well, take that number and multiply it by Number A, “Number of Planck Units in Sphere 14 billion in diameter X 12).

Now take this new number and calculate how many different ways you can recombine it so that every possible permutation is covered. You will then have a complete index of all imaginable universes. Not just all physically possible ones, but all logically possible ones. There will we one that is made entirely of hamburgers, and one that is just like ours except right up to this point, whereupon it all turns into chicken fat. And how large is that number. Well, it’s bigger than 42. The strange thing is a number like that could still be written in conventional notation on a small piece of paper. You can easily invent much larger numbers, but they do not refer to anything outside themselves. The number I have just described includes everything that could possibly happen plus everything that could imaginably happen in the universe. I would argue that you cannot have a number with a real referent that is larger than this. But I will leave it to someone else to express it as a whole number with an exponent.

Btw, wanna quick way you can generate numbers much larger than this? Here’s one. The operation # is defined as follows. 2# = 2 to the power of 2, 3# = 3 to the power of 3 to the power of 3, and so on. That is, 3 is raised so that there are 3 levels overall looking at the exponents. Thus 10# is 10 to the power of 10, to the power of 10, in an ascending series of exponents, until you get 10 layers. This number (10#) is far larger than the number I have just described. Now let us say G = googolplex. Look at the number G#. With 2 short definitions of G and #, you have created a number that is far larger than anything you could ever imagine. Myles325a 05:23, 23 August 2007 (UTC)

Where do all the animals go that die???

Where do all the animals go that die??? This question has been bothering me...why dont we see a bird just drop out of the sky from old age? Why dont we see squirrels all over the place that die from natural causes (road kill is easy to find). There are many more animals that have died than that are living, yet we dont find them anywhere. Where are they buried??

Anyone with insight, please fill me in. Much apprecaited...

Non-human animals don't bury their dead, but see decomposition for why we're still not up to our ears in corpses. As for birds dropping from the sky, it happens all the time when they've been shot. Birds dying of natural causes are presumably holed up somewhere rather than flying, just as people dying of natural causes are generally in bed rather than running down the road. --Sean 15:12, 17 August 2007 (UTC)

"birds always find a quiet place to hide" - Elton John SGGH ^speak! 15:19, 17 August 2007 (UTC)

Not all non-human animals don't bury their dead elephants bury their dead.--Fang 23 23:08, 23 August 2007 (UTC)

Scavengers are also a very important cause for the cleanup of dead animals (yes, I know it is part of the decomposition process). Re the old age/natural causes issue, you'll also find that not a lot of animals actually die of natural causes. Sick, injured or old animals tend to be the ones easily picked off by predators, so more often than not are effectively cleaned up before they get the chance to die of 'natural causes'. --jjron 15:24, 17 August 2007 (UTC)

Isn't being eaten by a predator just as much a natural cause as dying from a disease? Eran of Arcadia 19:05, 17 August 2007 (UTC)

If you like, but it's a different sense of "natural". When we say "die of natural causes" we usually mean old age or illness. --Anon, August 17, 22:03 (UTC).

Yes it is a natural cause, but in the context of this question if you die of old age as a natural cause you'll leave a carcase lying around, if you are done in by a predator, then no carcase - it gets consumed effectively immediately. --jjron 04:21, 19 August 2007 (UTC)

There is a colony of turkey vultures that roosts in a power transmission line tower near me. There are probably 200 birds there, each bird wieghs about 3 pounds, they must consume lots of carrion. I can imagine that as soon as an animal dies there is a race between all the bacteria, insects, and scavengers to consume the energy in the corpse. We are repulsed by corpses but in the natural world they are an easy source of energy that other organisms can exploit. -- Diletante 15:56, 17 August 2007 (UTC)

Round here, the corvids and gulls take care of the dead (I often see them pecking at roadkill, etc.). I noticed that there was a (pretty much whole, aside from being partially flattened) dead cat in the road one night last year. When I got up the next morning, the crows and magpies were pecking at what was left of it - which wasn't that much. The black-backed gulls will happily swallow dead birds (up to about the size of a starling) whole. I don't know what happens to the dead gulls - I've heard the 'gulls fly out to sea to die' and 'gulls will ferociously devour their own dead as soon as they keel over' stories but I have no idea if they're true or not. I can only recall ever seeing one gull corpse. --Kurt Shaped Box 17:39, 17 August 2007 (UTC)

Hi. The thing is, animals rarely ever die by your definition of "natural causes". I estimate that, by your definition, 10% of animals die of natural causes. Most are eaten by predators, few survive past their first year. Some are struck by lightning, killed by hunters, die from starvation, poisoned by human-made chemicals, killed in battle, struck by a car, trapped by an earthquake, trapped in a hurricane, etc. More die from disease than of old age. In fact, the same is true for humans. The bones of vertabrate animals sometimes embed themselves in the rock and get eroded or piled upon. The amount of organic matter on Earth dosen't change much throuout time. Thanks. ~AH1^(TCU) 22:39, 17 August 2007 (UTC)

One other factor to be considered is that small animals are "disposed of" much more quickly than large ones (like humans). While a human body lying in the woods might take a year to become a skeleton and several years for the skeleton to break down to unrecognizable pieces, a squirrel might become a skeleton and pelt in a month and an unrecognizable patch of fur under the dead leaves in just a bit longer. So, you aren't as likely to find that dead squirrel as the person. StuRat 20:33, 18 August 2007 (UTC)

Well, I've actually seen one. I was walking out of my house one day when suddenly BAM! this bird came from the heavens to land a few feet (I can only guess...10 feet?) away from me. It struggled for about 2 seconds and suddenly...you get it. I didn't know then, and went near it. It had keeled over but believe it or not, I could not make myself believe that a bird just...died in front of me. A few hours later, it was in a drain when I came back. By the way, it was a black pigeon. --Zacharycrimsonwolf 12:54, 19 August 2007 (UTC)

What caused the collapse?

(Added back by SteveBaker 15:05, 17 August 2007 (UTC) following accidental deletion from "Can you fault my logical and scientific proof for personal immortality?").

This thread makes me wonder -- what is it that causes wavefunction collapse in quantum mechanics? My (quite limited) understanding of QM is that it is "observation" or "measurement". Is that right? If so, what counts as observation? I just stumbled upon the page Consciousness causes collapse, which describes the theory that conscious observation is what causes wavefunction collapse. That sounds rather.. anthropomorphic? And anyway, do we even know what consciousness is? Can wavefunction collapse be brought about by something unconscious? Something "dead"? And a related question -- these descriptions of multiple world theories and questions of whether "you" live or die and which world "you" are in make me want to know -- what is this "you"? A couple people have mentioned how the "you" of the OP's thought experiment could lose "shells", body parts, memories, sensory stuff, etc etc... how about consciousness? How many such "shells" can you lose before there is no you left? Pfly 03:38, 17 August 2007 (UTC)

Well, that's the unpleasant thing. The Copenhagen interpretation says that the 'observer' plays a role and that 'observing' the event collapses the wave function. But that's really unsatisfying - it implies something special about human observers. What happens if a computer records the result? Why doesn't that collapse the wave function? Why are humans somehow special? Yuck! That makes an almost religious statement - I hate it. The many-worlds interpretation avoids that. In the Schrodinger's cat thought experiment the cat is in a dual state - alive and dead - but the scientist observing the experiment "collapses the wave function" by opening the box. That's a deeply unsatisfying thing. Suppose we regard the entire laboratory (including the scientist and the cat/box experiment) as a 'box'. The scientists wife, sitting at home is going to wait until he gets home and ask him whether the cute kitty at the lab is OK or not. From her perspective, does the wavefunction of the cat collapse when her husband open the box - or when he comes home and tells her what happened? I would argue that the situation of the scientist before she asks is no different than the cat before he opened the box. Until she asks that question, the scientist's wave function is in a dual state of knowing that the cat is dead and knowing that it's alive. When she asks the question, she too is in a dual state of grieving for the dead cat or not. The scientist no longer has a 'privilaged position' of being able to collapse the wave function. It's only collapsed as far as he is concerned. From his wife's perspective, it's still in that dual state. From her perspective, you could replace the scientist with a computer that opens the box, monitors the cat's life signs and emails her the news of the cat demise - and nothing is different. Hence, there is no difference between a computer observer and a human observer. This is (IMHO) a serious problem for the Copenhagen interpretation. If the scientist collapses the wave function - why doesn't the computer? Human brains have to be special in some way - and we know that they aren't. In the many worlds version of this, there is no problem. The atomic event goes off - there is a fork in the universe and now we have two universes - one in which the event happened and one in which it didn't. In both versions, the wave function has not collapsed from the point of view of either the cat or the scientist. A short time later, in one universe, the poison gas kills the cat and in the other it does not. From the perspective of the cat the wave function collapsed - from the perspective of the scientist, it did not. When the scientist opens the box, (at the same time in both universes) the wave function collapses - but nothing special happens to the cat - it was already alive or dead. From the perspective of the scientists wife, the wave function of cat and scientist has not yet collapsed. Everything works out OK. SteveBaker 15:30, 17 August 2007 (UTC)

I think the idea is that anything interacting with it counts as observing it. For example, when a photon hits an electron, both of their waveforms collapse. Different interpretations have different ideas of when it collapses. In one (I forgot the name) It's essentially always collapsed. In the many worlds interpretation which Steve mentioned, it never collapses. There is some evidence about where it collapses. For example, in the double-slit experiment is done with one photon at a time, it seems to go through two slits and cancel itself out in places. This is unlikely if the waveform has collapsed before entering the slits. — Daniel 16:31, 17 August 2007 (UTC)

My humble interpretation is that any observation is limited in scope. If the system in question is an electron spin, and the observer is some type of two-slit machine, then the wave function collapses when the machine measures the spin via a particle count at one or the other possible targets (e.g. up-spin electrons fly left, down-spin electrons fly right). The machine then reads out on some kind of a display (in the most simple form, the presence or absence of a hit counted on the particle detector). However, in the larger scope, a human has not yet checked the measurement, and the system status is still undetermined. The new quantum mechanical system is the superposition of the electron's spin AND the machine's possible readout. The coupled system depends on the actual spin of the electron and a deterministic relationship exists between the electron and the machine readout. However, the actual value is unknown to the outside observer; in this case, it is irrelevant whethe the electron's wave function is present or not, because the machine's ambiguity masks it... or equivalently, the machine may be deterministically coupled to an undetermined electron system. It doesn't matter where the uncertainty lies, because the total result of the measurement is still undetermined due to ambiguity somewhere along the line. You can continue encapsulating the "system" as far as you like - the human scientist who reads the machine is quantum mechanically undetermined between a variety of possible reactions to the measurement. The scientist doesn't collapse into a particular response, until "measured" or "observed" by someone else.

The final conclusion from my interpretation is that "collapsed" or "not collapsed" is entirely dependent on who/what is observing the system. From a particular frame of reference, there must be some level of ambiguity. Maybe this could be formalized as a "conservation of uncertainty" principle. Nimur 17:01, 17 August 2007 (UTC)

Daniel, arbitrary interactions definitely do not count as measurements for the purpose of wavefunction collapse. Atoms consist of protons and electrons in constant interaction via the photon field, but you can do the double-slit experiment with them. Light travels more slowly through air than through vacuum, implying an interaction with the air, but you can do the double-slit experiment with light in air. It's even been done with large molecules like buckyballs.

I seem to recall that Bohr associated collapse with "an irreversible act of amplification" -- that is, the collapse happens when so much of the world comes to depend on the state of the quantum system that there's no hope of erasing the information. This precludes any chance of observing a physical wavefunction collapse as something distinct from environmental decoherence.

I don't think it has ever, even in the early days, been a widespread view of physicists that the wavefunction collapse as taught in undergraduate QM (a discontinuous projection) was a physical phenomenon. Bohr certainly didn't believe it was. To him it described the updating of subjective knowledge. There's an objective component to the collapse, but that's not the collapse as such. -- BenRG 19:36, 18 August 2007 (UTC)

Time-lapse of bark growing

Does anyone know where I can find a time-lapse of bark growing? I think it would look interesting, but I can't find one. — Daniel 16:41, 17 August 2007 (UTC)

Bark takes many years to grow (Think "tree rings"!) - I think it's unlikely you'll find such a video. SteveBaker 17:36, 17 August 2007 (UTC)

Some types of trees, I'm thinking especially of many species of Eucalyptus, shed their bark every year. This is a significant contribution to making areas where these trees grow to being especially prone to bushfire. It would be possible to get a timelapse of this happening; I've got one in my backyard for example that has a clear period of say three months over summer where the bark changes colour, dries out, separates from the trunk and branches, and falls off to the ground. It would actually be pretty cool to do a timelapse of it, but I don't know if or where such a video exists. --jjron 04:29, 19 August 2007 (UTC)

Polarization filter for camera

Hidy ho. Could anyone tell me what degrees of rotation are best suited for what environments/effects? I have been using this filter for close to two months, but only lately found out how it is actually used. :) Thanks in advance! 81.93.102.185 17:51, 17 August 2007 (UTC)

You might find our article Photographic filter#Polarizer useful. The angle at which you set the polarizer depends on the effect that you're trying to achieve; there are some examples in the article. TenOfAllTrades(talk) 20:09, 17 August 2007 (UTC)

Photos of earless humans

I have read that Saddam Hussein often cut off the ears of his countrymen as punishment for one "crime" or another. I need a side view of such a person (for teaching auditory neuroanatomy) and have been unable to find one on the internet. Question: Are there hearing deficits in such a person, and what are they?–138.238.10.93 17:58, 17 August 2007 (UTC)superiorolive

http://news.bbc.co.uk/2/hi/programmes/newsnight/4603566.stm

http://www.cosmeticsurgery.com/articles/archive/an~179/#a1

http://www.earreconstruction.co.uk/ear-reconstruction.php

http://www.australasianbioethics.org/Newsletters/114-2004-03-26.html#iraqi etc87.102.5.166 20:49, 17 August 2007 (UTC)

As for the hearing deficits - I can only guess the answer is yes.87.102.5.166 21:07, 17 August 2007 (UTC)

Thank you for this. Experimental information from the brains of other species suggests that these mutilated pinnae will cause an inability or a least a serious deficit limited to the ability to locate a sound source in the sagittal plane, while leaving unimpaired the ability to locate sound sources in the horizontal and frontal planes. --User:138.238.10.93

Vision might also be negatively affected ... if the subject wore glasses. --Sean 18:21, 18 August 2007 (UTC)

The sizes of the Large and Small Magellanic Clouds

Ok I've asked this all over Wikipedia, in the Wikipedia talk:WikiProject Astronomical objects page, the Wikipedia talk:WikiProject Astronomy/Archive 1 page, and gotten no answer, so I'm asking here. Anyway, the Large Magellanic Cloud and Small Magellanic Cloud articles are in need of some attention. Specifically, nobody seems to know how big they are. There's been several contradictory and probably erroneous figures put up (some by me), ranging from 5,000 to 35,000 LYs (for the LMC). BTW the sizes up now are most likely wrong are misinforming people. Now, in going through a few Websites I've found various estimates for the LMC, this site [16] says 39,000 LYs, this site [17] says "about 30,000 LYs", this page mentions the LMC being "about 7 kiloparsecs" which is about 23,000 LYs, this NASA page [18] says "Spanning about 15,000 light-years or so", etc. The Celestia Astronomy programme I have says the LMC is 32,000 LYs in Diameter. As for the SMC, well this site (listed above again) [19] says it's "3 kpc" which is about 10,000 LYs, this page [20] also says 10,000 LYs, while Celestia says it's about 19,000 LYs big. This page (again listed above) [21] ambiguously says it's "under 20,000 lightyears in diameter". So, as you can see it's all quite confusing, can anyone clear things up? Does anybody know the diameters of the Magellanic Clouds? Or at-least where to get the information? I need some definitive source stating their sizes, or even just a size range, say "20,000 to 40,000 Lys" or something like that. But I can't seem to even get that, isn't there some generally accepted size in academia? And if so, does anyone know it? Thanks. --Hibernian 15:46, 24 July 2007 (UTC)

Well, these objects don't have hard edges that you can measure precisely - galaxies are 'fuzzy'. Do you measure the distance from the center to the utterly outermost star? If so, then the number you come up with will depend on how sensitive your telescope is because the last few individual stars out at the edges may or may not be visible depending on their brightness. So there isn't a "true" answer - in all likelyhood the density of stars in the galaxy as a function of distance from the center follows some kind of gaussian curve and as such may truly have no definite outer limit with one or two very loosely associated stars hundreds of lightyears away from the core. In that case, you'd have to pick some kind of metric like "98% of the stars are within XX lightyears of the center". Sadly, I can't give you a solid answer - but this does explain why the numbers you are seeing might be quite variable depending on who you read. If I were you I'd pick a range and say "various sources give a diameter of between 15,000^[1] and 30,000^[2] lightyears" and link each number to the source where you got that number. Incidentally - are all of those numbers diameters? Is it possible that some people are talking about the radius? SteveBaker 19:20, 17 August 2007 (UTC)

Thanks for the response. Yes I realize that galaxies have somewhat fuzzy edges, and thus it's very difficult to say what their Exact size is, but that's not what I'm after, I just need to know the generally accepted size range. For instance, we can say that the Milky Way is approximately 100,000 LY across, and we know sizes for many other galaxies. Now obviously 100,000 LY is only a general estimate, it could easily be 95,000 LY or 105,000 LY, etc. But that doesn't stop us from talking about Galaxy sizes in general terms. There are dozens of articles that state galaxy sizes, I just want to do the same for these two, but I'm running into difficulty. So what I really need at this point is to be directed to some source that is generally accepted amongst Astronomers. Does anybody know any reliable astronomy site on the net that would have the info? (Or a book?) If I can't find that, then I guess I'll have to do the next best thing and just list what the sources I can find say. --Hibernian 23:20, 17 August 2007 (UTC)

You are saying that the margin for error in stating the size is perhaps +/-5%. Take a look at that photo of the Large Magellanic Cloud. Try and draw a 'boundary' line around it! How can you possibly say where the edges of it are?! I could pick sizes over a range of 2:1 or more. It's a barred spiral that's been distorted by tidal gravitation from our galaxy...which makes it pretty much an irregular 'blob'! We aren't looking at a 5% margin of doubt - I'm not in the slightest bit surprised you can't nail down any kind of exact number! SteveBaker 01:52, 18 August 2007 (UTC)

I'm with SteveBaker on this one. Part of a serious study of astrophysics is the major paradigm shift away from precise quantities. This is not to say that scientific certainty is entirely out the window, but as a whole, the disciplines of cosmology and astronomy make it abundantly evident that they are not nearly as numerically accurate as other sciences. Even the age of the universe is known only to an accuracy of a few billion years, but despite furious debate on details, it's not really important to nail that number down exactly in order to have a fundamental understanding of cosmic evolution. Instead, these fields make a conceptual shift towards pulling bits of hard scientific truth from a very limited set of available observations with very handwavey details. Nimur 19:09, 19 August 2007 (UTC)

Sensu?

I am databasing plant pathology slides taken in the 50s and have come across one with rust on the stem which lists the species as "Cronartium coleosporioides sensu Peridermium harknessii [currently accepted taxonomic name = Endocronartium harknessii]." Both are now placed in the family Cronartiaceae, but Peridermium is listed as Incertae sedis. I am not sure what the sensu means in this sense. I have looked at the article for sensu, and it says is "used in taxonomy to specify which circumscription a given taxon is meant, where more than one circumscription has been defined." I couldn't make heads or tails of that statement. Is the slide depicting Cronartium coleosporioides or Peridermium harknessii (Endocronartium harknessii)? If this cannot be answered what would I need to look up in order to figure it out which one it is? 128.196.125.13 19:06, 17 August 2007 (UTC) (User:Sifaka unable to log in)

The statement will mean that the taxonomic name has had more than one definition, and that the text after the sensu should determine which one to use. In your case where you have two different species that are not overlapping, you are correct it does not make sense, and probably is a mistake. Is it possible that the author could not determine which of the two species the slide was sampling? Graeme Bartlett 03:42, 18 August 2007 (UTC)

Rotation of drinking-vessel as a means of controlling flow

When drinking a yard of ale, one rotates the yard in order to control the flow of beer, but how does this actually work? What forces are involved? DuncanHill 19:48, 17 August 2007 (UTC)

The excellent book The Flying Circus of Physics covers this: a normal tip of the glass would result in uncontrollable glug-glugs of air going up the glass and splashing precious ale outside the drinker's mouth; the rotating action swirls the liquid against the walls of the glass, creating a column of air along the central axis of the container, which allows the yard to be held at the desired angle for convenient quaffing. --Sean 20:33, 17 August 2007 (UTC)

Thanks, as a follow-on, is there an optimum speed of rotation, or does this vary with size and shape of the yard, or the amount of remaining beer? DuncanHill 20:35, 17 August 2007 (UTC)

Yes - it's something that pretty much comes with practice. I used to know a champion yard drinker (his best time was around 8 seconds!) - he had to learn each new glass because no two are ever really alike. He used a quick twist of the wrist to get the 'swirl' started - he could drink it faster (by far) than I could empty it over a sink! It's amazing to me that the world record is 5 seconds. SteveBaker 00:31, 18 August 2007 (UTC)

force applied by moving water

Is there any equation that someone could give me even if it is a rough approximation for the force a given obeject would have exerted upon it by moving water as a function of the waterspeed. Thanks! 209.112.207.90 22:40, 17 August 2007 (UTC)

Are you referring to drag? -- Kainaw^(what?) 22:56, 17 August 2007 (UTC)

The formula for fluid resistance says that the drag is proportional to the square of the speed:

$F_{d}=C_{d}\times 0.5\times \rho \times A\times V^{2}$

Where:

• F_d = The drag force (in Newtons)
• C_d = Coefficient of drag (0.35 for a car for example)
• $\rho$ = Density of the fluid in kg m^-3.
• A = Cross-sectional area of object at 90 degrees to the flow in m².
• V = Speed of fluid in m/sec.

SteveBaker 00:25, 18 August 2007 (UTC)

According to Stokes' law, the force of friction is proportional to the velocity, not to its square. It seems that the drag formula quoted by Steve and the equation of Stokes are two different limiting cases of the Navier-Stokes equations. What's the difference? (My guess: the former holds for high and the latter for low Reynolds number, corresponding to turbulent and laminar flow. Anybody knows for sure?) Simon A. 08:05, 18 August 2007 (UTC)

So this is why I keep old text books lying around. Anyhow, according to Physics for Scientists and Engineers, drag force is proportional to velocity for slow moving and/or small objects, while it's proportional to the square for fast moving and/or large objects. Large/small/fast/slow depend on what specific medium you're dealing with, although apparently "airplanes, sky divers, cars, and baseballs" are large and fast enough to experience the latter while moving through air. This text book is fairly introductory, though, and doesn't actually explain why any of this is the case. Someguy1221 10:27, 18 August 2007 (UTC)

Feynmann's physics textbooks (which are IMHO, the finest undergraduate texts available) go to some lengths to explain that all of the equations for friction and drag are useful approximations - so yeah - you'll always find cases when they don't work - or they don't work perfectly. This is why we build wind-tunnels! The worst part is that the "Coefficient of Drag" is exceedingly hard to calculate - so you pretty much end up having to guess - which means that all of your calculations are going to be very approximate no matter what. However, if you've gotta calculate some kind of an answer - or if you need a qualitative result - then this is the right formula. SteveBaker 14:47, 18 August 2007 (UTC)

Although it probably won't be much better than order-of magnitude, you could consider the rate of change of momentum of the water hitting the object, which is a nice example of a derivation from first principles. (not a very accurate one, though, as already mentioned, but much simpler than "real" fluid dynamics). 80.169.64.22 17:02, 18 August 2007 (UTC)

August 18

Strange creature ID needed...

I've had this pic on my HD for ages (can't even remember where I found it now). What the heck is this strange-looking fat green beastie anyway? --Kurt Shaped Box 00:05, 18 August 2007 (UTC)

There's something vaguely terrapin-like about it, for what it's worth. DuncanHill 00:09, 18 August 2007 (UTC)

I remember posting a link to it on usenet once and the general consensus there was that it was a photoshopped image created from several different animals. I dunno. --Kurt Shaped Box 00:11, 18 August 2007 (UTC)

Whoah, that's a weird picture. My guess is it's an armadillo giving birth. OK, I'm still perplexed. It looks not entirely unlike an armadillo, but where are the ears? If it really were a new baby, you should see the mother's tail. --Reuben 00:28, 18 August 2007 (UTC)

Cantor's giant turtle. They are super rare and live in Southeast Asia. Plug the name into Google Images for more. --24.147.86.187 01:00, 18 August 2007 (UTC)

I've looked. The CGT looks too skinny. --Kurt Shaped Box 01:11, 18 August 2007 (UTC)

What about the related Pelochelys bibroni? Looks a little "bulk-ier" (another image here). -- MarcoTolo 02:10, 18 August 2007 (UTC)

"Too skinny" does not seem to be a valid argument to me. The turtle on your picture sits on a pillow on a floor mat, i.e. it seems to be kept as a pet by someone. Maybe this someone has fed it too much and now it's overweight? Simon A. 08:20, 18 August 2007 (UTC)

I agree with 24.147 that it is probably Cantor's giant soft-shelled turtle (Pelochelys cantorii). Some of the images from a google image search look very close (and just as fat) as Kurt's image.--Eriastrum 17:49, 18 August 2007 (UTC)

Yeah, you may be right. Searching for the scientific name results in more hits. If it's not that particular species, it's pretty damn close. Thanks. --Kurt Shaped Box 19:39, 18 August 2007 (UTC)

Maybe Pelodiscus sinensis, too. Anyway, definitely in the Trionychidae family — what strange looking animals!

Speculation

This may be a stupid question, but here it goes anyway. Say if u bent a rod, I am wondering if the length of the smaller arc of the bent rod would be the same or shorter than the original length of the rod, even if there is only a tiny difference.

Shorter (slightly). The inside of the rod has to compress for it to bend. The outside of the rod has to stretch, so thats longer. See bimetallic strip for an interesting corollary of this principle.--SpectrumAnalyser 02:01, 18 August 2007 (UTC)

Not necessarily - we could imagine a material that would not compress easily but which might have no problem stretching. In that case the inner length would remain the same - and the outside would stretch a lot. Conversely, a material that is easily compressible - but hard to stretch (foam rubber for example), all of the change would be on the inside of the curve and the outside would stay the same length. I guess most materials will both squash and stretch to some degree - but it's not at all obvious that this is universally true. I think the nature of the material matters here. SteveBaker 14:40, 18 August 2007 (UTC)

That would require the stretching to be infinitely harder than compressing, or vice versa. I think it is possible to make a structure where the whole thing stretches or compresses when bent, but that is about the structure, not the material. — Daniel 18:25, 18 August 2007 (UTC)

If you look at a bent metal rod you can usually see little folds on the inside of the bend where the metal has pushed out to compensate for the shorter length. You can sometimes also discern stretching on the outside. Note that heating it allows the metal lattice to realign better, which is why metals bent more professionally, say by a blacksmith, don't suffer these problems. A good thing to try is bending a painted rod - the paint will usually crack or fall off where the length changes, but stay pretty much OK where the length hasn't changed. --jjron 04:43, 19 August 2007 (UTC)

Dreaming

A question above about dreams prompted this question from me, which I have always wondered about. If there is a fact that I personally do not know in real life, is it at all possible for me to have a dream of that fact ... or is that simply impossible on some level (physically / mentally / cognitively / consciously / subconsciously / whatever)? For example, in real life, I can't speak a word of Japanese. In one of my dreams, would I be able to speak fluent Japanese? For example, in real life, I do not know the square root of 378 (or the middle name of Tom Cruise). If I were asked those questions in one of my dreams, would I be able to correctly answer them? Thanks. (Joseph A. Spadaro 01:56, 18 August 2007 (UTC))

You may dream that you know the fact or answer or speak the language, but it is probably wrong. If you remembered what the answer was and checked it out in the waking world you will find out. It is possible that the answer is correct, and it may come from a part of your memory that you have never otherwise been able to recall. Or it could be a message from God, or if you are unlucky from a demon! Graeme Bartlett 02:24, 18 August 2007 (UTC)

I have found myself utterly convinced I knew and understood something that I actually did not. This was real life, unfortunately...So no, I don't see a reason you couldn't have the same feeling in a dream. Someguy1221 10:15, 18 August 2007 (UTC)

In a dream, I'm often convinced I know something, only to find out that I know the truth and it isn't what I thought it was while sleeping. Being convinced that an illogical event is happening while viewing it as logical is a common feature of dreams; even if you accidentally stumble upon the middle name of Tom Cruise, you'll have a hard time convincing me God did it. --Bowlhover 16:15, 18 August 2007 (UTC)

There is a theory that a great deal of learning happens while asleep, by reviewing recent activities and doing "batch processing" to figure things out that weren't apparent "in the heat of battle". For example, if a dog has tried to bite you before, but only when you are wearing a backpack, you might figure this out while asleep. Of course, the idea is that this new knowledge is to be transferred to the waking portion of the brain for future use, so the sleeping brain would only have additional knowledge for a short period.

If you had asked the more general question "can part of your brain know something that another part doesn't", then the answer is yes, at least in the case of multiple personality disorder. That is, one personality can have knowledge or skills that another can't access. However, this knowledge or these skills still have to come from somewhere, such as study or practice. It isn't possible for someone to know something (like Tom Cruise's middle name) without having learned it first. StuRat 20:15, 18 August 2007 (UTC)

Dark energy

Is the energy that is required to keep the Universe expanding simply dark energy? --M1ss1ontomars2k4 02:46, 18 August 2007 (UTC)

No, Dark energy, it it had sufficient density would cause the universe to contract. However it will not clump together by gravity as does other normal matter or dark matter, and so will tend to smooth out the universe. It moves too fast to settle down! Graeme Bartlett 03:44, 18 August 2007 (UTC)

Not quite right; at least in the simplest picture, where dark energy is a vacuum energy or cosmological constant, a greater density of dark energy would make the universe expand faster. It has an equation of state with negative pressure. --Reuben 06:01, 18 August 2007 (UTC)

The increase or decrease in the universe's scale factor $a(t)$ is governed by a differential equation

${\frac {da}{dt}}=H_{o}{\sqrt {\Omega _{m_{o}}a^{-1}+\Omega _{r_{o}}a^{-2}+\Omega _{v_{o}}a^{2}+(1-\Omega _{tot})}}$

where $\Omega _{m_{o}},\Omega _{r_{o}},\Omega _{v_{o}}$ are the present-day matter (ordinary and dark), radiation (CMBR), and vacuum (dark energy) densities respectively. (I cribbed this from Ned Wright, and it should probably go in FLRW, since it's much more convenient than the form that's there now.) So you can see that if $\Omega _{tot}\leq 1$, as it appears to be, then $da/dt$ will always be positive and the universe will keep expanding, regardless of the dark energy density. However, as a increases, the dark energy term will get larger while the other two density terms will get smaller, so eventually the expansion will be essentially driven by the dark energy alone. At that point the equation reduces to ${\frac {da}{dt}}=H_{o}{\sqrt {\Omega _{v_{o}}}}a$, which describes exponential growth. -- BenRG 18:55, 18 August 2007 (UTC)

What kind of squirrel is this?

I photographed a squirrel. It may be an Eastern Gray Squirrel, but I'm not sure. It was at the Blank Park Zoo in Des Moines, Iowa, though it wasn't part of an exhibit. grendel|khan 03:48, 18 August 2007 (UTC)

From the location (Iowa) I would expect it to be a fox squirrel. It's back does appear to be a bit more gray than usual, but that's probably still within the normal variation. StuRat 20:02, 18 August 2007 (UTC)

Hmmm, it's possible (even if not especially likely), that it could have escaped from an exhibit. --jjron 04:46, 19 August 2007 (UTC)

Holy crap that's the functionally extinct Eastern Grey Fox Squirrel called Sucop. Sucop is last female of her species and our zoo lost her just before we attempted to breed her with the last male, Ekaf! -- Blank Park Zoo 11:53, 19 August 2007 (UTC)

Comedians. Comedians are everywhere. —The preceding quasi-signed comment was added by Ummit (talk • contribs) 14:29, 19 August 2007 (UTC)

Who was Ed Hummel?

All I know is that his name (or part of it) turns up in the name of many hybridised succulent plants. There are also many references like ".. a Hummel hybrid .." on the Internet,. It seems like everyone knows one or more of the plants he produced, but these is no biographical information which I can find. I would like to know where he lived and worked, his birth & death dates, and if remotely possible, to find a list of the plant hybrids he produced. Thankyou 211.27.210.31 04:46, 18 August 2007 (UTC)

Ed Hummel, hybridist, of Hummel's Exotic Gardens, Carlsbad, California. See here. Xn4 01:18, 19 August 2007 (UTC)

pitcher plant

How do pitcher plants pollinate if they eat the pollinator? Clem 05:57, 18 August 2007 (UTC)

The "pitcher" of the pitcher plant is a modified leaf, not the flower. Thus the pitcher digests the body of whatever critter falls inside for additional nutrition. The flower is a separate structure that does not "eat" the pollinator. The flowers are usually held much higher than the pitchers, and the insect that pollinates the flower is often a different type of insect than that that provides food. The different types of carnivorous plants have varied mechanisms to prevent eating the pollinator.--Eriastrum 15:45, 18 August 2007 (UTC)

Transdermal Deca Durabolin

I know there is both testosterone gel and cream (also injections), but is it possible to have transdermal deca durabolin? Why or why not?

Stovetops

Why do hotplates not cause electrocution? How are they insulated, considering that most saucepans are made of metal?

The heating element is inside the hotplate - and is surrounded by an insulator - the metal (if present) on the outside does not carry any current.87.102.92.28 12:23, 18 August 2007 (UTC)

The insulator is some sort of temperature resistant inorganic solid.87.102.92.28 12:24, 18 August 2007 (UTC)

See heating element.--Shantavira|^{feed me} 13:09, 18 August 2007 (UTC)

Magnetic property of Hydrogen .

Is hydrogen diamagnetic ? 203.112.222.101 did not sign.

Yes it is repelled by a magnet. But only weakly. You may be able to exceed the gravity force with fields about 16 Tesla. as is evidenced by the frog levitation experiment. pyrolytic graphite and bismuth have a stronger diamagnetic reaction. Graeme Bartlett 15:41, 18 August 2007 (UTC)

Why doesn't air conduct current?

We all know that air doesnot conduct current.But why is it so?Air has numerous ions and electrons which is essential for conduction.Why the current cannot be passed through air molecules?--117.97.35.39 14:49, 18 August 2007 (UTC)

Lack of free electrons. See also breakdown voltage and electrical breakdown - the molecules in air need to be ionised first.87.102.92.28 14:55, 18 August 2007 (UTC)

The vast majority of 'air' is made up of empty space (vacuum), of the remainder most is in the form of unconducting uncharged molecules such as nitrogen.87.102.92.28 14:56, 18 August 2007 (UTC)

The original questioner mentions "numerous" ions. The issue at hand is "how numerous?" At sea level, "not much", or less than 0.002%. That's not enough to conduct current. Nimur 15:14, 18 August 2007 (UTC)

A quick run through the Saha equation for oxygen, using a room temperature of 298K, atmospheric pressure, and the ionization energy for dioxygen given at dioxygenyl and a generous value of 10 or so for the ratio $g_{1} \over g_{0}$ that I don't know, gives me a fractional ionization of the order $10^{-101}$. Away from thunderstorms and cosmic rays, then, there's a very good chance that all the times the troposphere has ever had even one such ion measure much less than a second. --Tardis 20:10, 20 August 2007 (UTC)

Anyone who has ever seen an electrical storm knows that air does conduct current, it's just a question of how well. It's a relatively poor electrical conductor, because, as already stated, it has few free electrons. StuRat 19:53, 18 August 2007 (UTC)

Could one say that air is a semiconductor, which requires a very high voltage before it conducts (lightning), thus being binary (conducts a lot or nothing at all), just the way we use semiconductors? Sorry, I barely know what I'm talking about here. DirkvdM 08:34, 19 August 2007 (UTC)

I do not believe that air can properly be called a semiconductor: "a solid whose electrical conductivity is in between that of a conductor and that of an insulator." Edison 18:16, 19 August 2007 (UTC)

That "binary" conduction mode feature would not be the mark of a semiconductor. This process is called dielectric breakdown, and is not the same physical process as semiconductor operation. Nimur 19:14, 19 August 2007 (UTC)

bush height

how does a bush/shrub know how high it has to grow?

My guess is genetics, but sometimes it goes wrong. I used to have a 3.5m high Mexican Orange Blossom (Choisya ternata) which all the gardening books say grows to 2.5m.--TrogWoolley 17:14, 18 August 2007 (UTC)

In the same way your body knows when to stop growing: combination of genes and environment. A number of genes interact to determine the size range and organism can maintain. Then environmental factors (like health, competition, access to nutrients, food, water etc) will determine where in that range the organism will reach. Rockpocket 23:21, 18 August 2007 (UTC)

Absorbtion rate through skin

Whats the highest possible absorbption rate through the skin for medicine?

I'd say it's pretty much instantaneous for some tiny molecules. Of course, most meds will be much larger molecules, so will be absorbed much more slowly, if at all. StuRat 19:48, 18 August 2007 (UTC)

[22] and Absorption (skin) might be useful. Nil Einne 11:44, 19 August 2007 (UTC)

Chagos Trench

What is Chagos Trench? By searching the internet, you get a answer like underwater canyon. But what it is in a plate tectonics context? The name implies it is one of oceanic trenches, but I think it is not.

Search Google with "directly from the trends of this ancient transform fault" and you get search result "directly from the trends of this ancient transform fault (the Chagos Trench and the. Mauritius Trench). For our purposes, the two determinations agree well ..."

Here an expert says he does not know anything about Chagos Trench.

Maybe someone could write an article with references?

--Pasixxxx 18:59, 18 August 2007 (UTC)

So, there are red, green and now blue laser pointers...

Anyone have any idea when violet laser pens will be on the market? --Kurt Shaped Box 19:52, 18 August 2007 (UTC)

I would expect there to be multi-colored ones first. With red, green, and blue, you can create any color. So, by allowing a person to adjust the intensity of each laser (inside one small case), you can produce any color you like. -- Kainaw^(what?) 21:39, 18 August 2007 (UTC)

How would you/would you be able to get yellow from that, as a matter of interest? --Kurt Shaped Box 21:52, 18 August 2007 (UTC)

In the RGB color model, yellow is a mix of full red, full green, and no blue. --24.147.86.187 22:15, 18 August 2007 (UTC)

this page has an interesting discussion of violet laser diodes that currently exist; apparently they have a tendency to make things nearby fluoresce (like a black light), which isn't that surprising. In practice it means that getting a pure violet waevlength out of a laser might be difficult, though maybe a mixing of multiple wavelengths as Kainaw suggests would work. --24.147.86.187 22:18, 18 August 2007 (UTC)

But then the whole point about lasers is lost: it is not monochromatic any more. --antilived^{T | C | G} 02:28, 19 August 2007 (UTC)

The whole point of a laser isn't its monochromaticness, it's the fact that it produces a largely coherent beam of light, that remains highly focused long enough to reach whatever powerpoint presenation you're aiming it at.--172.163.113.245 12:04, 19 August 2007 (UTC)

Or wherever you want your cat to run to... ;) --Kurt Shaped Box 16:25, 19 August 2007 (UTC)

Lasers were never monochromatic to begin with :-p (don't believe everything they tell you!) Someguy1221 20:05, 19 August 2007 (UTC)

On the subject of yellow: there's nothing stopping a single wavelength from appearing yellow: that's what rainbows do, after all. The primary colors aren't physics, but rather physiology: the number of them isn't even fixed. See dichromacy, tetrachromacy, etc. That we can make a yellow-looking laser beam in two different ways (finding a single yellow emitter or mixing a red and a green — although the result will not be coherent, exactly) is evidence that our color vision simplifies what's really there. --Tardis 17:48, 20 August 2007 (UTC)

How do I determine the age of an adult female budgerigar?

She's been used for breeding before, so she is definitely an adult bird. Is there any way of telling roughly how many years old she is?

See here. Xn4 00:55, 19 August 2007 (UTC)

IOW, unless she's wearing a leg ring, there's no way of knowing for certain how old she is, now that she's an adult bird. An 18-month old blue budgie (for instance) will look the same as an 18 year old blue budgie. I had a bird that lived 'till his late teens (poss. early 20s) and the only way that I knew he was old was because I knew how long he'd been with me and I knew that he had 'stiff' wings and a tendency to sleep a bit more, compared to how he used to be (his flock members would make an effort to feed him too - which I thought was lovely). I'm actually struggling to think of *any* bird that shows outward signs of ageing. --Kurt Shaped Box 05:58, 19 August 2007 (UTC)

Are you sure someone didn't acidentally kill the bird and replace it? Nil Einne 11:37, 19 August 2007 (UTC)

Na. This was definitely the same bird - unless someone was smart enough to find another bird with identical markings and demeanour and teach him to say exactly the same phrases... :) --Kurt Shaped Box 16:28, 19 August 2007 (UTC)

KSB- "I'm actually struggling to think of *any* bird that shows outward signs of ageing. See [23] for some specifics/examples. 38.112.225.84 05:47, 20 August 2007 (UTC)

Odd vision problem

Being a Wikipedia and RD veteran, there's no need to remind me of our rules about medical advice. I'm well aware of that, and I'm about to leave to check this with a doctor.

But a few hours ago I started to have this odd vision artifact. It's like a bad printing offset. I already ruled out the possibility of it being my computer monitor, as it follows the tilt of my head and I'm seeing it in books as well. What I first saw was a ghost image below letters, but I noticed it everywhere. Looking more into it, I decided to make a little experiment with each color, and each eye individually, using vertical and horizontal lines. The results puzzled me, since it looks like a freaky computer hardware problem. This is how it looks like, for both eyes (it's worse on the left one):

Anything red has a copy directly below. The green has a bit both up and down, but mostly up, and the blue colors leak up. This gives a weird colored ghost image at the top and bottom of things, and the ghost images are RGB-specific (magenta has two ghost images, a red below and a blue above). The distance is not constant and wobbles a bit. I've never heard of anything like this, and it looks kinda serious, so I'm checking it out with a professional already. Either way, I trust the power of the distributed knowledge of Wikipedians to take a guess of what this could possibly be. Have any of you ever heard of anything like it? I'm thinking it may be a chromatic aberration in my eyes. It makes a lot of sense, but in both eyes, at the same time, exactly the same way, and all of sudden? It's odd, but who knows?

Anyway, I'll be back later. Cheers! — Kieff | Talk 22:31, 18 August 2007 (UTC)

Hope it's nothing serious, man. I know that I have suffer from really weird visual artifacts myself when I have a migraine coming on. The first time it ever happened to me, I thought that I was going blind. --Kurt Shaped Box 22:41, 18 August 2007 (UTC)

I stared at those the longest time, thinking that the top and bottom examples looked identical, before I figured out the faint duplication. That's how bad my vision is. Absolutely not offering any medical advice, but you did not say if you wore glasses or if you had been tested for astigmatism. Hope your opthamologist/optometrist can help you. Edison 22:45, 18 August 2007 (UTC)

No, I don't wear glasses, and I've tested my vision last November with good results. — Kieff | Talk 04:41, 19 August 2007 (UTC)

You sure that it's not just a monitor issue? I had to give mine a wipe (didn't realize that it was covered in that much tar - heh) in order to see what Kieff was talking about... --Kurt Shaped Box 22:48, 18 August 2007 (UTC)

Yes, I already ruled out that possibility completely. — Kieff | Talk 04:41, 19 August 2007 (UTC)

I have astigmatism and it looks VERY like what you describe. You've said you are seeking professional advice, so of course - listen to your medical professional not to us! DuncanHill 23:11, 18 August 2007 (UTC)

Monitors with separate control electronics for each color (such as separate electron guns in a CRT sometimes have misalignments like you've shown. Are you sure this isn't a monitor problem? Nimur 23:19, 18 August 2007 (UTC)

Yes, I already ruled out that possibility completely. — Kieff | Talk 04:41, 19 August 2007 (UTC)

(Inappropriate medical comment removed here) There is something called a migraine aura, which can affect vision. A really bad migraine while your driving could be bad. You might want to think about having someone else drive you. --S.dedalus 23:29, 18 August 2007 (UTC)

I sometimes get auras, but do not get migraines. DuncanHill 01:16, 19 August 2007 (UTC)

Yeah, that happened to a friend of mine too. It must be rather surprising when it happens. --S.dedalus 05:02, 19 August 2007 (UTC)

No, I don't suffer from migraines. — Kieff | Talk 04:41, 19 August 2007 (UTC)

One can suffer from auras without migraines, or without ever having head a migraine headache before. It's called a "silent migraine" (somstimes known as "migraine sans migraine"). It's incredibly annoying, especially when you don't know what it is. They usually pass in under an hour.

The visual artifacts you're experiencing certainly sound related to migraine but I'd guess you'd have a really bad headache and other symptoms before or when that developed. As always see your doctor, or in this case an optician as well for professional, advice but I'd like to know if these symptoms are only at short distances. Whether it's short distances or not, if you're over 40 it could be related to a sudden decline in contrast sensitivity (fairly common), astigmatism as Duncan said, a specific symptom of macular degeneration problem or at a push cataracts especially if you've noticed any other problems in vision. If you've recently been light headed, had blackouts or had a knock to the noggin there are a number of possibilities, but by being smart and seeing the doc soon you should be able to sort it out before it becomes serious. Let us know how you are, all the best xx --82.12.235.69 01:55, 19 August 2007 (UTC)

I'm 21, and those things look quite unlikely. In fact, those problems you mentioned were ruled out by the doctor I visited. — Kieff | Talk 04:41, 19 August 2007 (UTC)

'Headacheless migraines' are definitely possible. Not sure if they're rare or not but I suffer from them occasionally. I get the 'auras', sickness and the 'unworldly feeling' - but no pain. One time, this was also followed by going completely numb down the right-hand side of my body and having trouble speaking. I honestly thought that I was having a stroke. *Very* scary stuff. --Kurt Shaped Box 05:12, 19 August 2007 (UTC)

Guys - this business of amateur medical diagnosis has to stop. I'm taking this to the talk page - I want to get an admin patrolling this group and handing out short term bans to people who break the rules. You are telling our OP that his symptoms are nothing important. If that causes him to fail to seek medical advice and this turns out to be symptoms of some terrible disease which maybe is fatal if not attended to (not that I particularly think it is - I just don't know) - then life insurance companies will come after you and you will get into deeper trouble than you can possibly imagine. This behavior has to stop. SteveBaker 02:57, 19 August 2007 (UTC)

I agree with you, but like I said, I'm well aware of this and I'm not gonna take medical advice from anyone here. That'd be a pretty stupid thing to do. All I wanted by asking this question is to probe the knowledge of various Wikipedians to see if anyone has ever heard of anything like this before, because I haven't. — Kieff | Talk 04:41, 19 August 2007 (UTC)

Well people, I went to the doctor and he's also totally puzzled. My eyes seem normal, my vision is nearly perfect, so he says, so none of this should be happening, as far as he knows, and as far as my eyes are concerned. I'll be back there during the week to discuss this with someone specialized in corneas to see if there's anything worth checking out, and also for further tests. I wonder if the effect will vanish by then, but either way, it seems to be an interesting case to study. Like he said, it could end up being a neurological thing, but that's still pretty odd. Anyway, thanks for the comments. — Kieff | Talk 04:41, 19 August 2007 (UTC)

Someone already mentioned it, but I have to say it again: Check out astigmatism. The difference in deflection could be caused by the difference in frequency. I believe one corrects astigmatism by using a lens with a bit of prism shape to it. This would seem to suggest that colors separating might be a normal symptom of astigmatism. At the very least, my astigmatism seems worse for red light sources (stoplights and brake lights) than other colors. --Mdwyer 05:37, 19 August 2007 (UTC)

Maybe, but I think they would have noticed that when they tested my vision, not only last night but also last year when I did some tests as well. They'd have to be pretty incompetent to miss that, I suppose. But I'll ask later this week. — Kieff | Talk 07:36, 19 August 2007 (UTC)

Is it still doing it? --Kurt Shaped Box 11:11, 19 August 2007 (UTC)

• Just make sure you ultimately see an opthalmologist - has more training than an optician or optometrist. Furthermore you can look at kerataconus (sp?) which is (rather scary) when your eyeball changes shape and starts to form a bit of a cone (pointed) which distorts vision - I believe the article has an example of the vision distortion. The other oddity is that your results seem to depend on colour - which is linked to the cones and rods at the back of the eye - but to my little knowledge that should not show double-vision on certain colours - or halo affect on certain colours. Try do some more experimentations for your own purposes - Do you have any known vision problems? Do you wear glasses or contacts? Do you suffer from dry eyes, short-sightedness, far-sightedness, etc. Does the problem change or appear differently depending on - angle, - distance, if you squint (lower your lids a bit). Test your self for colour deficiency. Please keep us posted, this is rather interesting.

Rfwoolf 15:03, 19 August 2007 (UTC)

Could you possibly have the beginnings of cataracts? I developed cataracts in both of my eyes and I started to get faint double images that eventually developed (over a period of a couple of years) into triple images of almost equal brightness. The images were offset by only a very small distance, so that the effect was that of double margins on one or two sides of an image. Once I got lens implants, this effect disappeared entirely, of course. I have never had migraine headaches, but once I had an aura that lasted a few hours--it was utterly terrifying because I had no idea what it was--thought I was having a detached retina! It took the form of a jagged C-shaped form that flashed and glittered. It was as if my vision was on a mirror that was shattered. I immediately went to my eye doctor who was able to tell me it was a migraine aura. Oddly it only happened once, and it was not accompanied by a headache. The human visual system is indeed a complex, bizarre thing!--Eriastrum 15:54, 19 August 2007 (UTC)

If I look from inside a room out of a window during daylight, I usually notice coloured stripes at the border of the window -- blue ones on one side and red ones on the other side. I've always assumed this to be a normal effect of some diffraction off a dark-light boundary, but it never occured to me that it might be a chromatic aberration in the eyes instead of a Fraunhofer diffraction at the object. But now I wonder: does everybody sees this or not? Simon A. 21:00, 19 August 2007 (UTC)

If I look at dark-light boundaries to one side of my field of vision, I get color fringes, which I eventually realized are due to chromatic aberration in my (fairly strong) glasses. Not diffraction, which wouldn't be strong enough to see in that situation. But this is not a separated image like the original poster describes. --Anon, August 19, 2007, 22:08 (UTC).

Kieff, you didn't mention it, but I assume you conducted your experiments without wearing any eyeglasses or contact lenses, right? I ask this because I've notice that polycarbonate eyeglass lenses have very noticeable prismatic effects away from their "central vision". I first noticed this at night where some decorative purple lamps on trucks were refracted into very separate blue and red images, but once you know the feect is there, it can be seen in a lot of circumstances.

Atlant 13:32, 20 August 2007 (UTC)

August 19

Why do we go blue?

OK, got asked an interesting question the other day that I couldn't fully answer to my satisfaction. When we get really cold our hands, lips, etc can take on a bluish tinge. Now I know all about the blood supply to the surface reducing to retain heat, etc, but what I couldn't answer was, 'why blue'? I don't know of any body tissues that are really blue, and despite what diagrams typically show deoxygenated blood isn't blue, so what's with the blue colour? The best link I can find is this, but can anyone explain it better? Thanks. --jjron 05:01, 19 August 2007 (UTC)

I’m not sure about your question. However, for clarification, here’s a link that talks about the red/blue blood thing. --S.dedalus 05:19, 19 August 2007 (UTC)

Thanks for this, but can I just cut anyone else off before this degenerates into a side issue and loses the question I'm asking; I don't want a discussion on the relative merits of representing deoxygenated blood as blue in medical diagrams, or anything like that. --jjron 05:36, 19 August 2007 (UTC)

LOL! A.Z. 05:45, 19 August 2007 (UTC)

(Nice comment A.Z. :-) ) Well actually, I was adding the link to help others understand the red/blue blood thing. I think I have found your answer. This link suggests that a lack of blood in tissue is the cause of blue skin. I would guess that the body shunts blood away from the skin to conserve heat when we are could. I’m still not sure why this would created the blue color, but if you read my previous link it mentions that this is caused by seeing the skin itself. --S.dedalus 05:52, 19 August 2007 (UTC)

That's correct. Your previous link says "Your *blood* does not ever *look* blue. The blue things you see under your skin are veins. Veins are really whitish in color but because the blood is dark and the skin difuses the light, the veins *look* blue." That doesn't really do it for me. How does something whitish in color looks blue just because there's a dark think inside of it and light difusion by the other thing outside of it? A.Z. 05:57, 19 August 2007 (UTC)

So after asking that I realized I didn't know what light diffusion was in the first place, and I searched for the Wikipedian article about it, only to find out there is no article. A.Z. 05:59, 19 August 2007 (UTC)

OK, thanks for discussion so far, but at the risk of sounding rude, can we please read the question before answering - I quote from the original question: "...I know all about the blood supply to the surface reducing to retain heat..." which is what S.dedalus's second answer addresses. And at the risk of answering my own question, I think S.dedalus's first link, which AZ discusses above, is actually talking about dispersion, not diffusion as it apparently incorrectly says. In other words, it would look blue for much the same reason as why the sky looks blue. --jjron 07:45, 19 August 2007 (UTC)

We do have an article on cyanosis. Bendž|Ť 09:13, 20 August 2007 (UTC)

Thanks, nice link, I had never heard of that term before. Sadly that article still doesn't really explain it very well (it more says what it is, rather than why it is so, and in fact there were some errors in the article that I've tried to correct), but we may be getting closer. --jjron 10:09, 21 August 2007 (UTC)

A chemical bond

I was observing my glass of sparkling water (with a piece of lime in it) this lunch, and i saw gas bubbles adhering to and thus collecting on the surface of a seed. Can anyone please tell me what is the name for this type of chemical bond? Is it a hydrogen bond, or not really? Thanks!

The surface of the bubble has more highly ordered water than found in the bulk liquid.

It's probably hydrogen bonding yes.87.102.4.148 08:53, 19 August 2007 (UTC)

Studies on bubble adherence show that hydrophobic surfaces (less ability to hydrogen bond) get less bubbles stuck to them.87.102.4.148 08:59, 19 August 2007 (UTC)

http://en.wikipedia.org/wiki/Nucleation ?

Veins

Why are veins greenish in color? Thanks.

What veins are you looking at? Read Vein#Color for some information. Someguy1221 07:18, 19 August 2007 (UTC)

Check the question two above called "Why do we go blue?". It's basically the same issue. --jjron 07:53, 19 August 2007 (UTC)

mimimum pixel size of lcd display

I've already found that camera lcds have pixel width around 50mm/500pixels = 100micrometers..

What's the smallest currently available pixel size?

Anyone know what the theoretical limit of pixel size would be?87.102.4.148 08:51, 19 August 2007 (UTC)

Dot pitch lists current minimum as around 100 micrometres. As for the theoretical limit well I don't know. For LCDs I would guess it would be several times the size of a silicon atom. According to 65 nanometer a crystal of bulk silicon has a lattice constant of .543 nm so if it's say 20 times this that would be ~11 nm. However anything smaller then the wavelength of light is AFAIK going to be extremely complicated to get to work and also probably pretty pointless so I would say perhaps around 750nm Nil Einne 11:36, 19 August 2007 (UTC)

I remember one of my prof's claiming that a superlense could be used to lower the theoretical and practical limits on pixel size...can't seem to find it in my notes. Someguy1221 20:00, 19 August 2007 (UTC)

A while back, IBM produced an LCD that was (IIRC) 200 dpi rather than the more-normal 90-100 dpi. It was very expensive but reported to be an exceptionally beutiful display (closely approximating what we can accomplish with printing on paper).

Atlant 13:37, 20 August 2007 (UTC)

Night vision

Is there any way that you can do to improve on your night vision? Other than stuffing yourself full on vitamin A's, I mean. --Zacharycrimsonwolf 12:40, 19 August 2007 (UTC)

Night vision goggles but I guess that wasn't what you meant. The obvious things are vitamin A which you already mentioned and adaptation. For example, go to a very dark room and stay there for several hours and do not exposure yourself to light. In an extreme you could live in a very dark environment for weeks or months but I wouldn't recommend it. If you believe in reincarnation, you could pray that you're reincarnated as a cat Nil Einne 12:58, 19 August 2007 (UTC)

Our night vision article makes mention of atropine eye drops. (At your own risk)--Shantavira|^{feed me} 14:21, 19 August 2007 (UTC)

What you could do is spend a lot time moving around in the dark, etc, in effect training yourself to be more comfortable functioning at night (as Nil basically suggests). While it may not improve your night vision in an objective measurement, you can become far more functional in that environment. --jjron 14:58, 19 August 2007 (UTC)

One interesting phenomena is that your night vision is better at the periphery of your vision, so try not looking directly at what you want to see. Tomgreeny 15:39, 19 August 2007 (UTC)

OT but I had eye drops to dilate my pupils once during an eye examination. I guess tropicamide or phenylephrine or a combination of both. I didn't have any sunglasses and walking out into the sun was horrible, even after giving it a while Nil Einne 17:47, 19 August 2007 (UTC)

I am skeptical about the usefulness of using drops to dilate the pupil, since the image quality may degrade due to the image passing through the optically poor outer area of the lens. Enhancing the sensitivity of the scotpoic vision via the rods is a more likely avenue. For a half hour before going out in the dark avoid exposure to any light. If you need some task lighting, wear red goggles or use red bulbs. This was done in World War 2 in submarines before it surfaced at night to preserve the night vision of the persons who would be on lookout. Binoculars with a large objective lens can collect more light than the naked eye and make fainter objects visible, as well as magnifying, if you do not want to do the obvious and use night vision goggles. Edison 18:09, 19 August 2007 (UTC)

Wear very reflective clothing to help light up your enviroment. Trust me my police jacket lights up the room sometimes if the background light is sufficient. SGGH ^speak! 18:30, 19 August 2007 (UTC)

You don't need atropine to dilate the pupil; just stay in the dark long enough. Our article on eyepatch mentions that the eyepatch of the stereotypical pirate might not be an invention of modern movies but actually have been worn by sailors with two intact eyes, to help them see better below deck. Oh, and as far as I know, a lot of people with only very slight myopia who usually don't use their glasses find them quite helpful when driving at night. Simon A. 21:21, 19 August 2007 (UTC)

Night vison article says that atropine is used together with night vison goggles, from personal expirience - normaly atropine worsens sight for few days, it is used so that pupil remains dilated in light, but it is dilated in dark anyway -- Xil/talk 21:24, 19 August 2007 (UTC)

An ophthalmology technician who specialized in both pediatric surgery, and refractive surgery for over 15 years, I can assure you that the article on night vision is inaccurate. Atropine is a very strong dilation medication, and in no way increases night vision. Yes, it allows more light onto the retina, but it also, as mentioned above, blurs the vision quite significantly. It does this because atropine relaxes the lens of the eye, and lens "flexation" is what helps us to focus. For example, hold your hand about 12 inches from your face, and focus on it. Then look beyond it, and focus on the wall. Your hand becomes blurry, and you notice a specific change in vision. This is because your lens is flexing. If your lens is unable to do so, your vision is compromised. This is also why people report they are unable to see well after having an eye examination. The more common dilation compound is Mydriasil (tropicamide.) (While phenylephrine is used in some offices, its use should be done with caution as it does have cardiac side effects with some patients.)

Atropine in pediatric ophthalmology is used to treat conditions such as "lazy eye" (amblyopia) when one eye does not see as well as the other; we would often prescribe one drop of atropine each day in the good eye, thus burring it intentionally, and forcing the "bad" eye to be put into use. Often a couple months of this therapy, and the child's eye would be fairly equal. There is really no way to improve night vision without using night vision goggles. However, there are a number of things that make night vision worse: Contact lenses (most people have issues with halos, starbursts, or foggy vision at night), cataracts, dry eye symptoms, fatigue, and in some cases, refractive surgery. If you find your vision has gotten worse progressively with regards to night vision, it is time to go see an ophthalmologist. ^Ariel♥Gold 03:02, 20 August 2007 (UTC)

You don't need the lens to do any work when focusing on distant objects (e.g., astronomy). Perhaps atropine would be useful then? --Tardis 17:26, 20 August 2007 (UTC)

Practice indirect observation (lateral vision). This is an astronomers trick. The central location where you tend to focus your eyes is full of cones. Around it is rods. If you train yourself to look slightly off axis you can observe more. In fact, you can try this with the night sky. You can see stars around the one you are looking at but they disappear when you stare directly at them. --Tbeatty 06:37, 20 August 2007 (UTC)

Yep, that's a most excellent point, Tbeatty, and certainly is true and reliable. Good point! ^Ariel♥Gold 06:39, 20 August 2007 (UTC)

The peripheral vision trick gets you better perception of motion and of very dim objects - at the price of reduced image 'sharpness' and a total loss of colour perception. But colour vision is poor at night anyway - so it's probably no great loss. SteveBaker 16:22, 20 August 2007 (UTC)

TI-89 Titanium Units

Why does my TI-89 Titanium think that all four of its preset units of temperature are "inconsistent units" and refuse to convert between them/add them, etc.? Thanks! Steevven1 ^{(Talk) (Contribs) (Gallery)} 21:23, 19 August 2007 (UTC)

Try using the tmpCnv() function. An example is $tmpCnv(0^{\circ }C,^{\circ }K)$ (the units need underscores, but I can't figure out how to make them show up there). anonymous6494 22:51, 19 August 2007 (UTC)

The problem with temperature is that it is used in two different ways.

(1) temperature

(2) temperature difference

So 20 F is a different concept from diff_20 F.

If you convert to celsius you get

(1) 20 F is equal to -6.66 C

(2) diff_20 F is equal to diff_11.11 C

I hope this clears it up. 202.168.50.40 03:55, 20 August 2007 (UTC)

Bald-headed birds and the sun...

Silly question I just thought about now. Do birds with bare heads (vultures or the marabou stork, for instance) get suntans on their heads and necks? --Kurt Shaped Box 22:34, 19 August 2007 (UTC)

Bound to- unless they have a built in UV screen--DieselFitter 23:37, 19 August 2007 (UTC)

That would be for a sunburn. Suntan would imply a natural ability to overproduce melanin in response to sunlight. Someguy1221 01:20, 20 August 2007 (UTC)

Just a guess but I would think bird skin is very similiar to lizard skin. I don't think they tan. --Tbeatty 02:08, 20 August 2007 (UTC)

Lizards don't tan in the same way humans do. They do disperse melanin throughout their melanophores though (as described in the article) they do so in a physiological rather than morphological manner. The situation in birds is not well understood, but its safe to assume that the bare head of vultures do not tan like humans would, for the simple reason that humans are extremely unusual in their tanning response. With a few exceptions (notably pigs and hippopotamus), even mammals do not respond to UV in the same way as humans. Rockpocket 06:24, 20 August 2007 (UTC)

Do pigs tan then? Does any animal? I doubt it.--Shantavira|^{feed me} 08:12, 20 August 2007 (UTC)

A quick and dirty google search gives reference to pigs with pink skin being susceptible to sunburn, and I see multiple reccommendations to apply suntan lotion to them. Stands to reason that if they can get a sunburn they could also get a "tan". Shhh though, if the sunscreen companies get wind of this they might think to test their products on pigs or, god forbid, hippopotamus. ;| 38.112.225.84 09:36, 20 August 2007 (UTC)

As I mentioned above, the ability to burn does not imply the ability to tan. These are biologically distinct processes. Someguy1221 19:54, 20 August 2007 (UTC)

Pigs should always have access to shady spots and a mud wallow as they burn readily in the sun. A wallow, as well as being cooling, is used by the pigs to cover their skin with a protective layer. DuncanHill 11:18, 20 August 2007 (UTC)

Correct me if I'm wrong - but aren't pink, shorthaired pigs a human creation? --Kurt Shaped Box 18:55, 20 August 2007 (UTC)

Maybe "we can tan" is the long-sought-after attribute of humanity that separates us from the beasts. --Sean 13:59, 20 August 2007 (UTC)

August 20

Cat Whiskers

Yo. I recently adopted a pair of kittens (approx. 8 weeks old), their mother was feral and the kittens were trapped and fostered. Anyways, one of the kittens I adopted along with a couple of the others that were available for adopting have really short, stunted whiskers; it kind of looks like they've been cut off or something. Any thoughts as to why this could be? Nutritional, maybe? Also, they will grow back in properly, yes? Thanks. 38.112.225.84 05:34, 20 August 2007 (UTC)

I'd look at them up close, do the ends taper off normally, or end abruptly ? If they end abruptly, they may have been cut or burned (they would look black at the end if singed). If they taper off, then I'd guess it's a protein deficiency. I'd expect them to grow back normally with a proper diet, in either case. If they don't, consult a vet. StuRat 11:04, 20 August 2007 (UTC)

Our larger cat used to chew off the whiskers of the smaller cat. I presume it was an aggressive act to establish a pecking order. After a while, this behavior stopped, but the pecking order was well established by then. Maybe your cats are exhibiting a similar behavior. Another possibility, as StuRat mentioned, is undernourishment or protein deficiency. Nimur 13:47, 20 August 2007 (UTC)

When and if the whiskers grow back the cat will have an important part of its sensory system back in action. Per Cat senses cats "see" with their whiskers to navigate in the dark and to tell where prey (or food or other nearby objects) are. They can sense nearby objects with them (perhaps by air currents). They are more functional than human whiskers. Edison 16:03, 20 August 2007 (UTC)

Hmmm, I'm going to have to go with some type of nutritional defeciency as the most likely answer I guess. Weird that some of the cats had these short whiskers and the others were normal. I remember reading some novel, can't remember the name, that referenced someone ridding themselves of cats by taking them some distance away and then cutting off their whiskers so they couldn't find their way back home. Just thought I'd share that. 38.112.225.84 07:12, 21 August 2007 (UTC)

Peeling

A question at the language desk led to the Hawaiian trouvaille "AKA'AKA'A", a word meaning "Skin peeling or falling off after either sunburn or heavy drinking". Now, this is supposedly from the book The Meaning of Tingo by Adam Jacot de Boinod, but I found it on several blogs - it's still possible that it was misquoted and then copied and mirrored. It's also entirely possible that the collector of this phrase has been had. But, assuming the translation is correct, what are they talking about? Does our skin peel off as a result from heavy drinking at all? ---Sluzzelin talk 07:14, 20 August 2007 (UTC)

Only if that causes you to fall asleep in the Sun, which may very well happen. StuRat 10:59, 20 August 2007 (UTC)

Skin can get rough from dehydration (from heavy drinking), but I wouldn't call it peeling. Of course, it could be a Samoan thing. Maybe they are prone to skin peeling when dehydrated. -- Kainaw^(what?) 16:11, 20 August 2007 (UTC)

Cognitive Error.

Do we have an article on a certain memory phenomenon caused by looking at something for so long that you seem to forget how it works. For instance, while reading this thread on Doctor Who, I found myself asking "is that really how you spell who?". This kind of effect happens to me fairly often, where a common word looks to me like it is spelled incorrectly, it's often accompanied by a thought that it looks like a ridiculous way to spell such a word, and it takes a good amount of conscious thought to confirm to myself that the spelling is actually correct. Do we have an article on it? I have no idea where to start looking. Does anyone else suffer from the same effect? Has anyone else noticed the effect with something other than language? Capuchin 09:22, 20 August 2007 (UTC)

Jamais vu? ---Sluzzelin talk 09:34, 20 August 2007 (UTC)

From time to time I definitely experience the exact same thing you describe Capuchin. Weird. 38.112.225.84 09:38, 20 August 2007 (UTC)

Jamais vu is a start, but i've never really experienced it with anything except written text. Also it's not a feeling of thinking that i'm seeing a familiar situation for the first time, but more a feeling that the word is obviously wrong despite being able to conclude, with more thought than i would normally have to use to check spelling of a word, that it is indeed correct. It also doesn't seem to matter what the word is, both long complex words and short simple words are equally 'up' for being obviously wrong. Capuchin 09:53, 20 August 2007 (UTC)

I get exactly the same thing sometimes as well. 147.197.230.174 10:24, 20 August 2007 (UTC)

I'd bet this is related to how, when you repeat a word many times, it seems to lose it's meaning. StuRat 10:55, 20 August 2007 (UTC)

This happens to me quite a lot. I find that it's more likely to be with short, simple words. Maybe this could be something to do with it being longer since you learned to spell them. Presumably when you first learn to write you will not have any clear method of learning/remembering words, but as you get used to it you will come up with methods and patterns that help you to remember. Or I could be talking garbage. Does anyone here teach young children?

Anyway, I also find it happens mostly with unusually spelled/pronounced words, for example 'length'. 'Who' is another one, and all the words with ough in them. Probably if you forget how to spell, say, complete, your brain will notice the connection with compose, compost, complement, deplete, replete, etc. Bistromathic 11:48, 20 August 2007 (UTC)

Yes the English written language can seem pretty ridiculous at times. Can't we just spel al awer words phoneticaly? Yes, this happens to me ALL THE TIME. I thought I was the only one...67.70.29.35 00:24, 21 August 2007 (UTC)

Support group, anyone? 38.112.225.84 07:06, 21 August 2007 (UTC)

Birth rates following wars

I was told at school many years ago that after a war the birth rate increased and more boys were born to replace those lost in the war. Is this true? Do statistics following wars prove this? If more boys are born, how does happen? Dianayork 09:45, 20 August 2007 (UTC)

I don't think there is more boys than girls after a war, other than the normal distribution. But it is unnecessary to replace those lost in a war as within a generation or two, the ratio of child-bearing age M/F will be restored to 50/50 because the birth rate is still 50/50. the only question is the size of the population. The skewed generation will die out leaving the correct ratio. --Tbeatty 10:02, 20 August 2007 (UTC)

(the statistics though? what do they say?)87.102.2.76 10:29, 20 August 2007 (UTC)

I believe that birth rates do often go up after major wars (such as the post WW2 baby boom in the US), but not to replace dead soldiers. The reason is that many people have "put their life on hold" while fighting the war, and afterwards want to "make up for lost time". Thus, a couple which would have had 3 kids during the course of the war will try to have them, instead, immediately after the war ends. I also doubt that any change in sex ratio occurs. StuRat 10:41, 20 August 2007 (UTC)

(the statistics though? what do they say?)87.102.2.76 11:50, 20 August 2007 (UTC)

Did you follow my link ? The baby boom article I linked to contains statistics (in graph form) on births in the US since 1934, which clearly demonstrates an increase in birth rates after WW2. StuRat 16:37, 20 August 2007 (UTC)

The question was about boys being born (assuming that more boys than girls die during wars) - at least that was how I read it...87.102.2.76 18:25, 20 August 2007 (UTC)

I took "the birth rate increased and more boys were born" to make two points: 1) The birth rate increased 2) More boys were born. I only addressed the first issue. StuRat 05:51, 21 August 2007 (UTC)

http://www.statistics.gov.uk/cci/nugget.asp?id=951 "Sharp peaks in the numbers of births occurred after both world wars"

http://www.actuaries.org.uk/files/pdf/library/JIA-084/0092-0096.pdf page 1 table 1 shows no blip in sex ratios post WW2. ?87.102.2.76 12:27, 20 August 2007 (UTC) There is a blip occuring during ww1/post ww1 is it significant though?87.102.2.76 12:27, 20 August 2007 (UTC)

From the source cited,

“ The sex-ratio does not, generally speaking, fluctuate wildly with time but only changes comparatively slowly. Table 1 gives the sex-ratio for live births in England and Wales over some 50 years of this century. The general impression is of a slow upward trend with periodic erratic fluctuations. This change may be due to the average age of the mother changing... ”

Now to answer your question definitively, one would need to establish whether the average age of mothers is definitely changing... and then, to establish a cause/effect relationship between the war and the average age of parenting...

I'm not a social scientist at all, so at best I can say that these cause/effect relationships are difficult to establish with certainty, especially on such a small blip. Nimur 14:06, 20 August 2007 (UTC)

I believe that this question over-estimates the number of men killed in war. I made a comment to a sociologist once about Russia practically losing a generation throughout the period of WWI and WWII. He corrected me by pointing out that while the number of men killed throughout that period was very high, it wasn't even close to half the men 18-35 in Russia at the time. I believe the U.S. lost a smaller percentage of men than Russia. I may be wrong about that also. -- Kainaw^(what?) 16:16, 20 August 2007 (UTC)

Even if far less than half, that's still rather significant in terms of demographics and population impact (it would be even more significant if they were women, however, as that would leave few women capable of childbirth). And yes, Russia had far more casualties than the US in WW2. StuRat 16:45, 20 August 2007 (UTC)

But here's the thing - even if after the war, the ration of child bearing age women to men was 70/30. In two generations it would be 50/50 because of a complete turnover in the child bearing population. --Tbeatty 19:22, 20 August 2007 (UTC)

Plus a 2 week old boy isn't going to be much use to a 20something female widow..87.102.2.76 19:49, 20 August 2007 (UTC)

Thanks. I often wonder if the people that died in both world wars had lived and reproduced, what would be impact on the world population now. Including of course the holocaust victims. Dianayork 11:31, 21 August 2007 (UTC)

Trends across period 3 of the periodic table

Hello all. THis *is* a homework question, but it's a small part of a huge assingment, and i'm looking for links (not answers), as i have been unable to find information.

I need information on a) the change in electorinic configuration and b) the change in net and core charge as you move across period 3 of the periodic table (from right to left).

Thanks for any help.Cuban Cigar 11:45, 20 August 2007 (UTC)

Period (periodic table) tells us that a period is a horizontal row, we even have an article Period 3 element.

Each of the elements in period 3 in the above link can be clicked on to link to the relevent article eg Sodium etc. The infomation you need should be in those articles (probably in the infobox on the right).

Ask again if you get stuck.87.102.2.76 11:55, 20 August 2007 (UTC)

Thanks a lot for the effort. However, i am looking specifically for the 'trends' across the 3rd period. The articles on the elements give information, but they say little on the trends.Cuban Cigar 12:06, 20 August 2007 (UTC)

If you make a list of for instance 'core charge vs column (group)' you'll be able to see any trends. Hint - in this case it increases - I leave the rest to you...87.102.2.76 12:30, 20 August 2007 (UTC)

Order: read Periodic trends!87.102.2.76 12:31, 20 August 2007 (UTC)

As mentioned, Periodic trends is the definitive article on the subject. I'm wondering if the title of that article should be renamed Periodic trends (chemistry) - as it stands, any recurring trend (such as an economic recession/boom cycle) could be called a "periodic trend." Nimur 13:56, 20 August 2007 (UTC)

I think that would only be neccessary when periodic trend (economics), periodic trend (history) articles actually exist!87.102.2.76 14:25, 20 August 2007 (UTC)

Added 'fix' to Periodic trends - a link to the disambig. page trends is that ok?87.102.2.76 15:28, 20 August 2007 (UTC)

Ha i managed to extract the information thanks to all who helped.Cuban Cigar 22:01, 20 August 2007 (UTC)

BIOLOGY

which is the Ovoviviparous roundworm? what type of egg is found in flat worms? how does cellulose digestion in ants carried out? which type non-chordates is bioluminescent? differences between nematocyst & trichocyst? interstitial cells in hydra are totipotent.give reasons?

This would not happen to be a homework set of questions would it? Have you read articles on roundworm, flatworm, termite, bioluminescence, nematocyst, trichocyst hydra (genus) (which is potentially immortal) or morphallaxis? Graeme Bartlett 13:44, 20 August 2007 (UTC)

Chemistry

Why is the SiH4 highly reactive so as to get easily hydrolyzed with aqueous alkali, while CH4 is nearly inert to it?

The usual explanation is that Si can expand it's octet whereas C can't - known as octet expansion - Si has 'available d orbitals'

4 is the maximum coordination number for c

Whereas Si can increase it's coordination number past four eg [SiH₄(OH)₂]^2- is possible (quite stable)

[SiH₄(OH)₂]^2- + 2H_{20 = 2H2 + SiH2(OH)2 + 2OH^- and so on...}

Look at the compounds of sulphur - you will see that stable entities such as SiF₆^{2- are stable but have no parallel in carbon chemistry.87.102.2.76 15:43, 20 August 2007 (UTC)}

chemistry

Bit confused with the term O_3 hole

Do you mean ozone hole or a Crystallographic defect in a oxygen containing lattice?87.102.2.76 15:50, 20 August 2007 (UTC)

Look at ozone hole. Flyguy649 ^talk _contribs 15:50, 20 August 2007 (UTC)

Per Flyguy; an underscore is sometimes used to indicate that the character that follows is meant to be subscripted. So O_3 → O₃ → trioxygen, usually called ozone. TenOfAllTrades(talk) 15:54, 20 August 2007 (UTC)

Petrochemicals

What is going to happen to the chemistry industry when we "run out of oil"? Where are we going to get all of our hydrocarbons from, especially ethene, the most commercial produced organic compound? From ethanol? --Russoc4 15:40, 20 August 2007 (UTC)

plants seem to be the probable source of carbon compounds when the oil and coal runs out.

There may be a major shift in the types of polymers produced when that happens - nowadays polyethene is common - because we can get ethene. In the future we may see a lot less of it and tend to use (if possible) 'starch' or cellulose based products if possible eg rayon.

It should still be possible to produce ethene from the cracking of vegetable oils.87.102.2.76 15:49, 20 August 2007 (UTC)

It's certainly a concern - and one that isn't mentioned enough. But I suspect (without proof) that the nature of supply and demand will mean that we won't ever literally "run out". It will be that the cost of crude oil will gradually increase as demand continues to rise but supply decreases - to the point where it's not economical to burn the stuff in car engines anymore and we are forced for cost reasons alone to switch to sustainable alternatives such as ethanol. What remains of the oil will probably last the chemical industry a long time. As an important feedstock for plastics and such, it's going to push up the price of some materials. As the stuff gets progressively rarer (and hence more costly), more and more parts of the industry will find alternative materials as a starting point - and what's left will become used in more and more specialised niches. There are precedents for this. Lots of industries used to be dependent on whale oil (and other whale products) - all adapted with the dramatic cutting of supply. SteveBaker 16:07, 20 August 2007 (UTC)

Also, expect plastic recycling to become far more prevalent as the product becomes more expensive. StuRat 16:31, 20 August 2007 (UTC)

Eagle Project

I am currently a Life Scout in The Boy Scouts of America and am currently thinking of things to do for my Eagle Project. I want to do something to help the enviroment. I was leaning towards planting trees in a city park or school. WhAt I want to know is what kind of tree would be most beneficial. I live in North East Texas near DFW. Or if someoen could point me to a website that deals with this kidn of thign that would be great. Also, when I do this project, I will need to raise money and if I have any money left over I need to donate it to an organization. I want to donate it to an organization that deals with this sort of thing. Thank you very much. schyler 15:53, 20 August 2007 (UTC)

I would definitely concentrate on native Texas species - they'll survive best without lots of careful treatment afterwards. As for funding, you might try to hook up with companies who are trying to be 'carbon neutral' - they realise that they are pumping CO₂ into the atmosphere (bad for the greenhouse effect and global warming) - and some of them are starting to try to offset that by paying people to plant trees on their behalf. Trees eat up about their own weight in CO₂ and pump it back out as oxygen - so if a company pushes out a hundred tons of CO₂ per year, they would (presumably) be interested in getting enough trees planted each year to compensate (ie enough to grow into a hundred tons of trees). Really big businesses would probably only do this sort of thing through a very organised company or whatever - but I bet you could find some small businesses in your area, figure out how much CO₂ they are putting out in a year (or causing to be put out because of electricity they use or something) - and approach them with the idea that they could offset this nasty behavior by planting trees. I bet that if you approached a small-ish sized business with a well-thought out proposal - and made them some posters they could stick up saying "We are now carbon-neutral!" (or whatever) - then they'd hand over the price of some baby trees and whatever you need to get them planted. You can turn this into a project including: science (coming up with the carbon numbers), art (drawing the posters), marketting (putting your plan to the businesses) and some outdoorsy stuff (planting and tending for the trees). SteveBaker 16:16, 20 August 2007 (UTC)

Just as an aside, it is not entirely clear that carbon offsetting by planting trees is quite as simple as all that. It sounds nice and green but the actual science of carbon sinks is a bit more complex, I gather... --24.147.86.187 20:44, 20 August 2007 (UTC)

Well, yes - sure. But we're talking about a boy scout activity here - I think we can allow a measure of approximation. SteveBaker 00:13, 21 August 2007 (UTC)

The National Arbor Day Foundation sounds like a natural choice for the charitable donation, to me. StuRat 16:25, 20 August 2007 (UTC)

Utah Mine Disaster

I guess that I am more comfortable placing this question in the Science (as opposed to the Miscellaneous) Help Desk. I certainly know nothing about mines or mining. So, in simple layman's terms, why is is it that "they" can't find those six miners in Utah? Specifically, I wonder the following (probably naive) questions. (1) Why is it not simply a matter of re-tracing their (the six miners) steps? (2) Is there no technology available and/or industry practice/convention followed whereby outsiders would be able to tell the location of trapped miners? Or whereby trapped miners are able to relay that location information to the outside? And (3) Are there no methods/means of communication (cell phones, walkie-talkies, emitting beeps, GPS, etc.) that are used in such instances? I mean ... mining has been around forever ... and this is certainly not the first time miners have been trapped. To me (an outsider, unfamiliar with the industry), it seems like they are reinventing the wheel, as if no miner in the history of the world has ever been trapped before? What is the logical explanation to all this? Thanks. (Joseph A. Spadaro 17:05, 20 August 2007 (UTC))

I'm not a mining engineer, but will do my best to address some of your questions. (1) Re-tracing steps. This can be virtually impossible following a collapse - as well as clearing débris from the access levels & shafts, safety work (eg. shoring up the roof) must be done at the same time, to protect the rescuers. Also, more than one level may have been affected by the collapse - imagine a multi-storey buiding collapsing, one cannot simply go to, say, the 2nd storey, as the collapse will have destroyed access routes, and jumbled the different levels together. (2 &3) Mines in the developed world are likely to employ a variety of communication techniques underground, however, radio is largely ineffective through rock, cell-phones & GPS do not work at all underground, and physical connexions (telephone) are likely to be destroyed in a collapse. Infra-red imaging may be of some use, as may radar techniques to identify potential voids (open spaces, which may have survivors in them). Any survivors would be likely to attempt to communicate their location by making noise (eg, banging on structures which could conduct sound) and they may have bleeper devices, however, they are likely to be injured, exhausted, and suffering the effects of thirst, hunger, and heat. They would also be aware that banging around in unstable ground could precipitate further collapse. Sadly, mining remains an inherently dangerous occupation, and those who benefit us all by their delvings are all too often killed in their efforts. DuncanHill 17:27, 20 August 2007 (UTC)

Short versions are

1. Retracing steps would involve going through unstable recently-caved-in rock, possibly the worst mine-related material to work with. Remember, the rescue effort was shut down because rescue workers were killed in a related cave-in.
2. Not with certainty. Rescue efforts are based upon knowing the general areas in which the miners are located and where the most survivable areas are, coupled with best-guesses as to the extent of cave-ins. That leads into...
3. Not really. Rock does an excellent job of attenuating electronic signals, particularly the weak ones that miners could have transmitters for. A high-powered signal from the surface might reach the miners; a return signal is unlikely to reach the surface. Sound, however, is a relatively common signal, though it requires that miners have the ability to strike something appropriate both hard enough to be heard and long enough to be located.

You may be interested in this NYTimes article, which notes the problems with #1 and the lack of proven success with locating miners via sound. Consider also that it's not "reinventing the wheel" when the wheel in question has never been adequately invented to begin with. — Lomn 17:30, 20 August 2007 (UTC)

A widely known way to save lives after cave-ins is to have regularly spaced "safe areas" where miners can go in a cave-in, which have air, water, food, and a hard-wired communication line to the outside world. Why don't they have them ? Because they are expensive. Why don't government safety organizations like the US Mine Safety and Health Administration force mines to have them ? Because many, perhaps most, "safety" organizations in the US have been subverted from their original purpose of protecting people from businesses to their new purpose of protecting businesses from people (who might win lawsuits, had the safety organization not given the business it's seal of approval). StuRat 17:51, 20 August 2007 (UTC)

Supporting StuRat's point, note that Richard Stickler, the current administrator of the US Mine Safety and Health Administration only gained his job through a recess appointment by George W. Bush. His appointment was strongly opposed by both the United Mine Workers union and the United States Senate, even though the Senate was then in Republican hands and ought to have been sympathetic to a Bush appointee.

Many of the "regulatory" agencies in the United States no longer actively regulate the industries they were meant to oversee.

Atlant 18:11, 20 August 2007 (UTC)

Hmmmmmmmmmm. There is no feasibility to use, say, those scent-smelling dogs ...? The kind that sniff drugs or find criminals on the loose? (Joseph A. Spadaro 18:53, 20 August 2007 (UTC))

I haven't heard of them being used, but they may have possibilities. However, mines may have a lot of strong smells in them already, and I doubt there are many dogs which can sniff out a man covered in coal-dust buried under tens of thousands of tons of coal. DuncanHill 19:05, 20 August 2007 (UTC)

The problem with search dogs is that someone would need to take them down close to where the miners are, and others would need to clear the way of rubble and shore up the mine supports, and that would risk the lives of those people, just as earlier rescue workers were killed by a subsequent cave-in. StuRat 05:44, 21 August 2007 (UTC)

I have found a fascinating paper on-line here [24] which discusses various factors affecting survival after mine accidents, and looks at such issues as air-supply, "safe havens", etc. DuncanHill 23:11, 20 August 2007 (UTC)

Tension in a string tied between two supports

Imagine a situation very similar to a suspension bridge. A string is tied between two rigid supports and the length of the string is more than the actual distance between the supports. Now, tying a weight and allowing it to hang down would exert wht all forces ??? I think one would be the tension but does the support also exert some force such as compression ???

Please enlighten.

The string would be under tension only, but each support would be under compression (from the weight of the support itself plus the half the weight of the string and mass supported by the string) and also under bending and shear (from half the weight of the string and mass supported by the string). StuRat 17:37, 20 August 2007 (UTC)

Precisely. See suspension bridge.--Shantavira|^{feed me} 17:38, 20 August 2007 (UTC)

Also, if the string is attached off-center to each support, then each support would undergo torsion (from half the weight of the string and mass supported by the string). StuRat 18:00, 20 August 2007 (UTC)

MPG: reality versus EPA ratings

This is more a technology question than a science question, but here goes. Anyone have info on how cars tend to perform in real life, mileage-wise, versus EPA estimates? I'd always been under the impression that the estimates are optimistic. I know the EPA estimates have been revised for 2008 (and possible a few times before that?) to be more accurate. I have a 07 model (which, in my understanding, would be rated a couple mpg lower with the '08 method) and it consistently gets better than advertised mileage. It's rated at 20 city, 28 highway, and we very regularly get 31-32 highway, and 22ish city. I did get 28 (mostly) highway once, with several passengers and their stuff in the car. This is with fairly brisk acceleration, whenever there is enough open road to allow such a thing. Did we get lucky with this car? Is it all down to driving habits? I've noticed that if you don't realize how soon you can upshift (at surprisingly low rpm for a 4banger) your city mileage quickly goes to hell. Have the estimates perhaps already gotten more conservative? Any idea how common it is to get better than expected mileage? Friday (talk) 18:33, 20 August 2007 (UTC)

I am a strong believer in driving habits. I had a 1994 Saturn SC1 that I sold last weekend. I regularly got 35-40mpg. I now have a 1997 Toyota Corolla. I regularly get 35ish mpg. I know people with the same vehicles that get less (even half) what I get. However, they do not drive the speed limit. They do not accelerate slowly. Instead, they speed and jackrabbit start from every stop. -- Kainaw^(what?) 18:37, 20 August 2007 (UTC)

Sounds reasonable, but the odd thing in my case is that I do speed and start quickly compared to most other cars on the road (many of whom appear to be asleep at the wheel.) I've noticed that mpg tends to be higher when average speed is higher (according to the car's mileage/trip computer). I have always chalked this up to less time spent stopped, though. I would rather change lanes to get around stopped cars than stop myself. Time spent idling and not moving seems to kill the mpg pretty quickly. Friday (talk) 18:47, 20 August 2007 (UTC)

As I noted, I drive the speed limit. I rarely stop/idle. Traffic lights tend to be set to the speed limit. So, I continually see the same thing. Light turns green. The guy next to me floors it. Two blocks later, I pull up next to him at the next light just as it turns green. He floors it. Two blocks later, I pull up next to him at the next light just as it turns green... Also, driving 65 on the highway (speed limit on our highway) means that I rarely have to slow down. People behind me who have a desire to do 80 have to slow down and go around me. So, all in all, idling isn't an issue. -- Kainaw^(what?) 22:33, 20 August 2007 (UTC)

Oh come on - get real. Yes, a lot of people say that - but they conveniently forget that the guy who accellerated hard from the lights will (maybe one time in ten) squeak through the next light when you get stuck there - or make the oddly timed filter arrow on a turn - or be at the front of the line of traffic and therefore be able to do a 'right on red' when you get stuck behind a car that's going straight on. That can easily save him a couple of minutes each time it happens. Sure it makes a nice story ("Oh I drive so carefully but I still get there just as fast") - but let's be honest here: it's bullshit. Simple mathematics and a dose of statistics will show that. Even if you stick to the speed limit, drag racing style starts and lethally dangerous lane changing will get you there faster. Driving slowly and carefully (laudable though it is) can only allow you to break even with the guy who's going nuts in the best of all possible circumstances. Obviously we must consider the law and safety issues in driving reasonably - but the argument that driving fast doesn't get you there sooner is just wishful thinking. This is the science desk - not religion. SteveBaker 23:18, 20 August 2007 (UTC)

A lot depends on the car - and a lot depends on how you drive it. It's well known that hybrids don't get anything like as good milage (by maybe a factor of two!) compared to the EPA ratings because by luck, the EPA test conditions are a very good match for what the hybrids can manage. For most cars, you can reach the EPA number if you drive them carefully. A few years ago, I had a car (a MINI) that was claimed to be able to do 35mpg. I was getting 28mpg. But I knew why that was - and I decided to find out whether I could actually manage 35mpg. So I filled up the tank, turned off the A/C checked my tyre pressures and drove very gently - trying to keep the revs between 2000 and 3000 rpm by never stomping on the gas, not going over 60mph and shifting gears (it's a stick shift) much sooner than I normally would - keeping a close eye on the tachometer. I also used cruise control whenever possible to avoid the little variations in speed that also eat gasoline. It took me two weeks to run through that tank of gas - the most boring two weeks of driving I've ever done! But when I filled it up (noting carefully how much was needed to fill the tank and dividing by the milage on the tripmeter) - I was astounded to discover that even doing a mixture of town and freeway driving, I was getting close to 42mpg! 42mpg is a LOT more than the EPA estimated (35mpg) and VASTLY more than my usual 28mpg. So for that car (at least) the EPA numbers are too optimistic for a 'typical' driver (well, OK I am a bit lead-footed) - but quite pessimistic for a really, insanely fanatically careful driver! On the other hand, my daily commute went up from 25 minutes to 35 minutes each way. Over two weeks, I spent 200 minutes longer in traffic and saved $15 in gas! However, that's less than $5 per hour. Do I really want to pay myself minimum wage for being stuck on the freeway? Hell no! So now I'm even more lead-footed than I was before! SteveBaker 23:02, 20 August 2007 (UTC)

The EPA just revised their mileage estimating routine to make it more in line with reality.Gzuckier 14:16, 21 August 2007 (UTC)

My girlfriend insists that she uses a tank of gas about every 300 miles. I drove the same car, went up to 330ish miles and still had a quarter tank. I'm pretty sure it's just the way you drive. --Wirbelwindヴィルヴェルヴィント (talk) 16:41, 21 August 2007 (UTC)

birds

I have a 1st grde question I need to know if the hummingbird is the bird that has the fastest wing flaps. I think I am right but need to be sure. Thank You.22:34, 20 August 2007 (UTC)63.3.15.1≥ MDS

Yes. According to The Bird Almanac: A Guide to Essential Facts and Figures of the World's Birds. ISBN 1-55297-925-3., the Amethyst Woodstar and Horned Sungem hummingbirds both have maximum wing beat rates of 90 per second. -- MarcoTolo 22:43, 20 August 2007 (UTC)

Yes - they do. But there is a lot of difference between the biggest hummingbirds and the smallest ones. According to our article on hummingbirds, the Giant Hummingbird's wings beat 8–10 beats per second, the wings of medium sized hummingbirds beat about 20–25 beats per second and the smallest beat 70 beats per second. There might be some other kinds of birds that could manage 10 beats per second and be faster than the giant hummingbird - but nothing can come close to the speed of the little ones. To get a feel for how amazingly fast that is, your fingers are about as long as a hummingbirds' wing. See how many times you can 'flap' a finger up and down in 30 seconds. SteveBaker 22:49, 20 August 2007 (UTC)

And note your fingers won't make a humming noise. This is where the name 'hummingbird' comes from. A frequency over 30 Hz will produce an audible sound. But this makes me wonder - at what frequency does a mosquito flap its wings then? Judging by the pitch that should be in the thousands. Is that possible? DirkvdM 18:38, 21 August 2007 (UTC)

Speed limit "c"?

This idea has been a nuisance since I first thought of it. I know there must be something really simple and elementary that I’m over looking here so be kind in your responses. The scenario is as follows. Suppose we have a sequence of satellites (planets) each traveling in the same (forward) direction. Each satellite travels at a velocity of 50,000 km/s (say) relative to the satellite before it in the sequence. The first is at rest and the 6th and last one is therefore traveling at 250,000km/s relative to the first (or use any speeds and the appropriate number of planets, the question is the same). Then suppose we have a space ship taking off from the 6th satellite reaching a speed of 60,000km/s (say). Shouldn’t this be impossible as its relative speed to the first satellite is greater than c? However, as far as I know it is perfectly possible to create an object that can accelerate to such speeds (theoretically) relative to earth. Why can’t earth be the 6th planet? How would the space ship “know” whether its motion is being compared to that of the 1st or 6th planet or any other satellite?67.70.29.35 23:54, 20 August 2007 (UTC)

Speeds don't add. If A is going at speed u with respect to B's rest frame, and B is going at speed v with respect to C's rest frame, then A is going at speed $(u+v)/(1+(uv/c^{2}))$ with respect to C's rest frame. This is smaller than $u+v$ and never exceeds c provided u and v don't. This formula is sometimes confusingly called "the velocity addition formula" even though it's not an addition. It's better called "the velocity transformation formula." It looks like Wikipedia's article is currently under velocity-addition formula, unfortunately. -- BenRG 00:56, 21 August 2007 (UTC)

Well, there are two things to consider.

• Firstly, there are no 'absolute' velocities - the word "relativity" in "Einsteins theory of relativity" means that you can just choose to decide which of your satellites and space ships is considered to be 'stationary' and choose to measure speeds relative to whatever you decided to pretend is stationary - what's more, the rules of physics and outcomes to all experiments are identical no matter which thing you choose to be stationary. This doesn't seem that weird to most people. If you've sat in a train with another train next to you - when the other train starts moving forwards, you get a really powerful feeling that you're moving backwards and that the other train is stationary.
• Secondly (and this is the weird part), we humans are used to a nice simple world where you can say if one object (object 'A') is moving away from me at speed X and it launches another object (object 'B'( at speed Y (relative to A) - then I should see B moving at a speed (X+Y). That simple arithmetic is really close to the truth at 'normal' speeds (like anything under a million miles an hour). But sadly, the universe doesn't actually work like that. From the point of A, it did indeed launch B at speed Y - but because A is moving away from me at anything like the speed of light, distances and times as measured by A seem to be 'wrong' to me - which means that as far as I'm concerned, A's measurement of B's speed is also 'wrong' - so instead of B's speed seeming to me to be (X+Y), it's X plus a bit less than Y. That 'wrongness' gets worse and worse the faster A moves away from me - and (by an amazing cosmic conspiracy), the result is that the speed of B NEVER seems to be faster than light - no matter what speed A is moving and no matter how fast A launches B. Weird - but true.

So, in your case, you're assuming you can just add those speeds together from the perspective of you standing off to the side of all of this complicated stuff. But as soon as these things start moving fast, their time and space distortions start to mess things up - and all of that always makes sure that nothing goes faster than light. It doesn't matter that A launches B which launches C which launches D, E, F - all we care about is that if 'F' is zipping away from me at a good fraction of the speed of light - then when it launches it's satellite, it's view of time and space will be so messed up that from the standpoint of someone watching all of this, the speed of the satellite will ALWAYS be less than 'c'. SteveBaker 01:06, 21 August 2007 (UTC)

Here's the kicker, everything else is modified to keep two fundamental principles: 1) the speed of light is constant in all frames and 2) energy is conserved. That means mass, lengths, time and frequency of light all change depending on the frame of reference. --Tbeatty 05:40, 21 August 2007 (UTC)

The way I've alwasys looked at this problem is that, we assumed that the time is constant through out the world, and we can measure the time from the other side of the world instantaneous. This assumption is the cause of all the confusion. Think about this scenerio: You and I are standing next to each other, both of us are holding a very accurated watch and have the exact same time. I start to walk away and point my wacth at your direction so you can tell the time on my watch. After I walked 5 meters, you look at both watch and see exactly one second had passed on both watches, you then say I moved with speed 5 m/s. This is what we experience in our world. There is one important factor we ignored so far is that, how is it that you can see my watch from 5 meters away? Simple, light travelled from my watch to yours, in exactly 5/c seconds (distance over speed, make sure it makes sense). If both our watches read the SAME TIME, then how is it after signal from my watch after 5/c seconds still the same as yours? The only logical interpretation is that my clock must have gone a little bit slow, and reads (c/5) second slower. Put this in cosmic scale, you will see relativity does make sense.192.53.187.183 14:44, 21 August 2007 (UTC)

August 21

Quantum Immortality....WTF?

I read the question posed earlier about the possibility of immortality because of the random nature of quantum mechanics and my confusion can be summed up in my headline (excuse my French…err…acronym). I just want to have one thing cleared up to start. In such an experiment, according to quantum mechanics, the actual state that we see “forms” (or collapses to that state) when we observe it. Is the state that we see (dead or alive) the “real” (and only) state or do both states still exist? (theoretically). If it is the former than perhaps WTF was an understatement.67.70.29.35 00:07, 21 August 2007 (UTC)

Well, that's really at the heart of the problem. Rather than think about quantum immortality (which is controversial for lots of other reasons as well as this one) - let's just think about Schrödinger's cat. The question boils down to: What is the state of the cat between the quantum event setting off the poison gas (or not) and when the experimenter opens the box? What you believe depends on how you interpret the results of some very weird experiments. If you go the 'many worlds' approach then the whole 'collapse' thing doesn't really come up - dead kitty in one universe, live kitty is in the other - both things happen at once - but not in the same universe - hence no 'collapse'. But there are other ways to interpret the results that say that indeed the cat is both alive and dead at the same time in a 'superposition' that is only resolved into an actual state when someone "observes" it (this is the 'collapse' of multiple superposed cat states back into a cat that is most definitely either alive or dead). But other people claim that far from the state of the cat collapsing, instead the scientist has now entered into the superposition - so when he opens the box, the scientist is now in a superposed state of knowing that the cat is alive and knowing that the cat is dead - if he's disgusted by the stink of the dead cat and doesn't eat his lunch - then his sandwich gets dragged into the superposition - then his wife phones and asks how he enjoyed his lunch - and now she is dragged into the superposition...and so on until all of the universe is superposed...which is a lot like 'many worlds'. There are several other ways to look at it. But the effect is definitely there. Work on quantum computers and quantum cryptography rely heavily on the fact that superposition or multiple universes or SOMETHING weird is happening in actual reality. SteveBaker 00:39, 21 August 2007 (UTC)

Oh come on, are you actually saying that if you built a schrodinger's cat box in real life something weird would "happen in actual reality"? The cat would either die or not, period.. it might mess with quantum theories or whatever but real life? Are you sure? --froth^t 04:11, 21 August 2007 (UTC)

They come up with macroscopic examples like the cat in the box to illustrate something that *really is happening* in the world. Yes, it's real, in the real world (unfortunately, for people like me who will never understand QM). The world making Newtonian sense is just not true. See double-slit experiment#Quantum version of experiment. --Sean 05:09, 21 August 2007 (UTC)

Yes - sure we're saying that's EXACTLY what would happen in real life. The cat would simultaneously be alive and dead until the scientist looks into the box...according to SOME interpretations of the experiment. In other interpretations, the entire universe is duplicated at the moment the unstable atom decides to split (or not) - and the only difference between the two resulting universes are that one contains a dead cat and the other contains a living one. In other interpretations, the atom is in a superposition state but as soon as it tries to influence a macroscopic effect it's quantum state collapses. (Of course this is a thought experiment - and a practical experiment would have to ensure that the box was perfectly soundproof, etc so the experimenter wouldn't be able to know the state of the cat until he opened the box. That may be entirely impractical in practice - but as a thought experiment, this is entirely valid!) SteveBaker 13:28, 21 August 2007 (UTC)

Shouldnt this be rather easy to disprove? Just perform the experiment a couple hundred times and if you're still alive, proudly declare that you just killed a couple hundred people and that your universe is spectacularly lucky to be the only one who has proof that quantum immorality is real. Of course nothing is proved or disproved if you die.. --froth^t 04:23, 21 August 2007 (UTC)

Quantum immorality is a different issue altogether :) Capuchin 07:20, 21 August 2007 (UTC)

The problem with your argument is that only your consciousness has proof that quantum immortality is real. The chances are tiny that anyone else in that universe has proof of quantum immortality besides you. You are a statistical anomaly. In a way it is "your" universe caused by your consciousness being quantum immortal. Capuchin 07:20, 21 August 2007 (UTC)

The deeper problem (if we're talking about quantum immortality again - and IF it's true (which it's probably not)) is that there are an infinity of universes. If you believe in the theory, you can put a gun to your head, pull the trigger and find that it mysteriously fails to fire. You do this 100 times with 100 different fatal suicide techniques - and you find you'll survive all of them. Everyone around you is convinced that quantum immortality is true - you win a nobel prize - science, religion and philosophy changes everything. However, it's only been proven in that (very, very rare) universe where the gun jammed, etc. In the majority of universes (such as the one I currently inhabit) your brains splattered everywhere and you died - and we all find it hard to believe in quantum immortality because we have no evidence that it ever happened. The fact that nobody in all of history appears to have been saved miraculously after a series of wierd suicide efforts doesn't mean it won't happen - it just means that in almost all of the universes, you died the first time you tried it. People die all the time in the universe that you and I happen to inhabit right now - but quantum immortality would say that there are other universes in which those people are still alive. There are universes where Julius Ceasar is still alive - amazingly! We just don't happen to live in one of those because such things are astronomically unlikely. SteveBaker 13:28, 21 August 2007 (UTC)

Original questioner speaking. Hmmm... perhaps I should rephrase the question. First I’ll start out with a few premises.

1) 1 state is actually seen when the cat in question is observed. 2) All subsequent observers will agree with the claim of the first observer (who’s only claiming what he saw). In other words, they will agree on the state of the cat.

If the premises above are accepted (I doubt they will be), then I can only say it is utterly absurd to say that only 1 state exists after the observation and yet 2 states before, as if observing the object somehow changes the reality of it. And what about each subsequent observer? If the first observer sees the cat as dead, then how can the cat still exist in only 1 state for the next observer who hasn’t yet observed the cat, because to him it should still exist in both states!? Again...wtf? This can only, I repeat ONLY, work if there are multiple (parallel) universes. Therefore, why can’t QM assert the existence of these universes as confidently as it can assert the seemingly absurd existence of a cat that is both dead and living at the same time? 67.70.29.35 07:54, 21 August 2007 (UTC)

Utterly absurd? Sounds about right. "If you think that you understand quantum mechanics, then you don't understand quantum mechanics" - Richard Feynman. Capuchin 10:00, 21 August 2007 (UTC)

Yep - wise words. (Feynman is my hero!) Quantum and relativistic effects are so totally alien to us, it's essentially impossible for us to truly 'feel' the consequences of them. We've evolved over millions of years to live within a range of sizes, speeds, gravitational pulls, etc. We see everything within those ranges as 'normal' and 'intuitive' - and things that only happen at other sizes, speeds, etc as utterly beyond our minds to fully comprehend. That's no surprise. A hypothetical creature that existed only at quantum scales would find our existance utterly incomprehensible. The important point here is that you cannot - must not - use common day-to-day experience as a way to interpret the universe at scales beyond that experience. The universe isn't weird - we're just hopelessly limited in range. But many of these seemingly impossible things are actually used in day-to-day devices. You have a flash memory in your PDA/Phone/MP3 player? Well, those devices only work because electrons can (essentially) spontaneously teleport. Super-secure communications systems are just beginning to be developed (eg between banks) that use quantum entanglement (which is a related phenomena to superposition). These things actually WORK - so the underlying science must be pretty close to the truth no matter how weird you think it is. SteveBaker 13:28, 21 August 2007 (UTC)

Steve, Perchance did you watch Richard Dawkins' talk at TED about why we percieve reality as we do?

And to the OP, don't worry, everyone else thinks that it's weird too, just that it being weird doesnt prevent it from being accurate. Capuchin 14:12, 21 August 2007 (UTC)

No, I didn't. Watching it now... SteveBaker 19:20, 21 August 2007 (UTC)

The physics of quantum mechanics is all contained in the mathematical formalism, which makes clear predictions about the outcomes of experiments of this kind. Your two premises are both empirically testable statements about the world, and the theory says they're both true. Where you get into trouble is when you start asking what the outcome of a measurement would have been, in the absence of any actual measurement. Asking whether the cat was alive before opening the box is a question of this type. Quantum mechanics doesn't answer this kind of question, and the formalism doesn't suggest any obvious way to answer it in general, and there's no real consensus about whether there is a sensible answer, or what it would be. In other words, it's not clear what quantum mechanics is saying about the nature of the universe. The interpretations are various people's guesses about what the nature of the universe might be, to give rise to rules like this. This isn't just a metaphysical question, since the interpretational difficulties become impossible to ignore when you try to quantize gravity. Hopefully a theory of quantum gravity will rule out some of the interpretations, or make it clear that they were on the wrong track. Of course, quantum gravitational effects are so weak at ordinary energies that this may remain metaphysics for a while.

Contrary to what many people seem to believe, the formalism does not say that the cat is "both alive and dead" before the measurement, or that the double-slit electron "goes through both slits". There's a wave function which may be in a superposition of alive and dead states, but (a) there's nothing in the formalism to connect superpositions in the wave function to anything empirically real, and (b) a superposition of X and Y is totally different from a state that's both X and Y. For example, a superposition of a cat in one box and a cat in another box is entirely different from a state with cats in both boxes, or half a cat in each box (assuming you could even define what that means). There's nothing "ghostly" about superpositions: the live cat and dead cat in the superposition are in no sense superimposed in the box.

Schroedinger's cat is not really a very good thought-experiment, because there's nothing essentially quantum about it. Cats are classical objects, and everything about the experiment is classical: you randomly gas the cat, and open the box, and the cat is alive or dead. The uncertainty principle doesn't meaningfully apply in cases like this. So my last two paragraphs were really about thermodynamically reversible systems, which are inherently quantum in their behavior. -- BenRG 16:22, 21 August 2007 (UTC)

But that's the whole point of the thought experiment. Schroedinger wanted to point out (in an especially memorable manner) that these teeny-tiny quantum weirdnesses can't simply be buried as something that doesn't have huge consequences. Because it's possible to amplify a small quantum event into something as macroscopic as a dead/not-dead cat, we have to start really worrying about what this means to our perception of macro-scale reality. SteveBaker 19:17, 21 August 2007 (UTC)

Psychomotor Retardation

What are the sympotms of psychomotor retardation and is it cureable/treatable?

I've created a new section for the OP. We have a stub article on psychomotor retardation. Wikipedia is not a source for medical advice, so if you're asking for such, please consult a doctor. Splintercellguy 03:42, 21 August 2007 (UTC)

"travel adaptors"

My roommate is a student from Cambodia on a study abroad program.. his laptop power brick ends in a frightening power plug with big blades and a spike! He brought a little travel power adaptor so that he could plug it into our power socket.. with wide eyed horror I insisted that he plug it in across the room, lest he fry my computer when the device fails. My question is: are these travel adaptors safe? How can a AC-to-DC power converter just work on some random cambodian power network, and then suddenly (literally) adapt to 120V/60Hz? And will plugging it in across the room do anything to protect my power supply? :) By the way, I already saw our article on the subject, and it didnt help --froth^t 03:54, 21 August 2007 (UTC)

What do they look like? A simple cubic structure with your local plug on one side and his local socket on the other? Or is like a slab or box with something more in between? If it's the first one it's simply changing the physical contacts and maintaining direct electric contact between the two incompatible plugs, and doesn't contain any electronics at all; If it's the latter it's probably a transformer and some regulators that converts American voltages to the voltage that most of the world uses (240V). Either way it's not gonna blow up your computer (unless you have a very bad power supply and it happens to send a surge through the mains). --antilived^{T | C | G} 04:20, 21 August 2007 (UTC)

It's the first. Like I asked before, how does the power brick handle the unexpected electricity specs? --froth^t 04:25, 21 August 2007 (UTC)

I believe they can automatically switch between ~120V and ~240V, the same range of voltages any US made power supply can handle. Just take a look at the back of your own laptop's supply and see its specs. Someguy1221 05:20, 21 August 2007 (UTC)

See also Switched-mode power supply. When I went to Dublin last year (from the US), I just had a small set of adapters. When it was time to plug in my laptop or digital camera, I simply found the adapter that took my friendly-looking two blade American plug and converted it for the gigantic socket in my hotel room. The power supplies took care of recognizing the higher voltage/lower frequency and putting out the 5 or 12V DC that my electronics wanted. --LarryMac | Talk 15:53, 21 August 2007 (UTC)

Earth science

Why Himalayan orogeny is explained to have happened in an episodic manner that is sometimes 'faster' and at other times passing through a 'lull"?

Sorry, but the simple answer to this is that that is how it happened. As a historical event the Himalayan orogeny happened the way it did, and if the evidence suggests it was episodic, then that's what has to be said in explanations. Or was your question meant to be more along the lines of "why can orogeny occur in an episodic manner?" --jjron 10:04, 21 August 2007 (UTC)

I believe the question is why the two plates don't move together at a constant rate, but rather at a variable rate. That is, what causes this variation ? StuRat 13:00, 21 August 2007 (UTC)

pitcher plants

How do pitcher plants pollinate if they eat the pollinator? Clem 08:17, 21 August 2007 (UTC)

They don't eat the pollinator, see the reply to your identical question 3 days ago. Capuchin 09:26, 21 August 2007 (UTC)

Sorry, couldn't find it. Clem 13:37, 21 August 2007 (UTC)

No problem :) Capuchin 14:17, 21 August 2007 (UTC)

What is true

People use to fall in love at the first sight...This has happened many ion front of my eyes..OUt of this few loves have led to marriage and few have dropped...And there are another type of love which appears in lovers heart after spending a long time with them by working in same project or studying in same class or so...In this the later one can be accepted that each one understands each other in their working days and then begins to love...BUt the former case is unpredictable...How can a love at the first sight be a true love?..Isn't it due to facial attraction?..If he and she are beautiful enough to fill in their heart, then an attraction in name of love appears...So is the 1st case a true love?..As you see many such love at the first sight has proved too...what's the big thing behind this? — Preceding unsigned comment added by 122.164.117.111 (talk)

• "No, this trick won't work...How on earth are you ever going to explain in terms of chemistry and physics so important a biological phenomenon as first love?" --M@rēino 14:17, 21 August 2007 (UTC)

You get preprogrammed by several factors; your parents, tv and movies, experiences with other people, etc. then when you meet somebody who fits this preprogrammed template, you project a lot onto them. Most of the time, they don't turn out to be that ideal person you have in your head after all, even though they reminded you of him/her. Gzuckier 14:20, 21 August 2007 (UTC)

Pneumatics Vs Hydraulics

HI There are many systems using Pneumatics and Hydraulics for lifting or generating enormous thrust power in some stuffs like a bulldozer or a crane or maybe a driller machine or in locomotives etc...But the key point of my doubt is that which among these two technique is powerful?..A pneumatics based system(air pressure) is used in many things such as in Trains and automobiles that require air brakes at very high PSI and in some boring(earth Bore) machines for getting a water hole in earth..Such machines generate air from the big fans and compress it through various chambers and then increase it to high presure..whereas in Hydralics many applications will be based on pulling or lifting...such as brakes in automobiles, bulldozer using it to move the arm to lift or crush...and even in car crusher(correct me) too...What I understand is that air is compressible at high pressure(compression rate) where as a fluid based system (hydraulics) isn't compressible..I maybe wrong but is this correct?..Or is there any valid physics laws for this?.... — Preceding unsigned comment added by 122.164.117.111 (talk • contribs)

The compressibility and thus density isn't very important, I believe that only the pressure (in PSI or Pascals) is important in determining the amount of work done. One advantage to using hydraulics with oil as the liquid is that such a system is self-lubricating. An advantage of using pneumatics is that gases can be moved more quickly, especially over long distances, without generating as much heat. If air is used, the gas is free and does no harm when released. Water is almost free, but can rust steel. StuRat 12:54, 21 August 2007 (UTC)

(EC) See Pneumatics#Comparison_to_Hydraulics. Note that air is also a fluid; it's just not (normally) a liquid. --Sean 12:57, 21 August 2007 (UTC)

In fact, compressibility does make a difference. Because liquids aren't compressible, whatever happens at one end matches whatever happens at the other. If the brake pedal goes down, the brake pads squeeze. Period. (barring springing a leak or other failure). With gases, you can have a lot of action at one end and nothing at the other, just build up pressure. The other important factor is that when the gas is compressed, if it is released there is a lot of residual energy built up which now expends itself, which is not true with liquids. This can be useful, but more often not. For instance, when a container of compressed gas springs a sudden leak and starts rocketing around; with liquid under pressure, a sudden leak just spits a bit and that's it. Gzuckier 14:25, 21 August 2007 (UTC)

That's why one has to bleed the air out of hydraulic brake systems. If you get even quite a small bubble in your brake lines, you certainly notice how spongey your brakes feel! For systems that need a large reservoir of stored energy (like the air brakes in busses), pneumatics may be preferable because air is lighter than hydraulic fluid. SteveBaker 18:27, 21 August 2007 (UTC)

Nettles

Why are dock leaves always found where nettles are growing? - Kittybrewster (talk) 11:41, 21 August 2007 (UTC)

I'm not sure that's always true - but even if it was, it shouldn't come as a surprise. When someone first got stung by a nettle, looked around to find something to ease the pain - they wouldn't have tried a plant that only grew 100 miles away! If there were a 'cure' for nettle stings, it would have to be a plant that shares similar habitats to nettles - similar soil conditions, similar moisture and sun requirements and so on. Hence, it's far from a coincidence that these plants tend to grow nearby. Sadly, I believe though that dock plants are becoming relatively rare - and I've seen plenty of places in the Ipswitch area where there were a ton of nettles - but no dock leaves anywhere to be found. SteveBaker 13:01, 21 August 2007 (UTC)

I looked for this information less than a month ago and found nothing. I hope someone knows! Capuchin 14:21, 21 August 2007 (UTC)

And Steve, Ipswitch??? Capuchin 14:21, 21 August 2007 (UTC)

isoxazole

what are the reactions and medicinally important compounds of isoxazole? — Preceding unsigned comment added by Dineshbph (talk • contribs)

Our article on isoxazole provides some information on this. If you have specific questions, we can try to help you out—but please don't post entire homework questions directly on the Reference Desk. TenOfAllTrades(talk) 12:53, 21 August 2007 (UTC)

Palmetto Bug communication

I have many precautions against bugs entering the house and surviving for very long. However, over a number of years the following scenario has occurred over and over again. I'll notice that for some reason I am unable to go to sleep as when perhaps you forget to take out the garbage and your mind will not shut down until that task is complete. Try as you will, you can not go to sleep, until you recall that the garbage needs to be taken out. In this scenario after anywhere from one day to a week or so of not being able to go to sleep you may realize that something like not taking out the garbage is responsible so you stop trying to go to sleep and get out of bed, turn on the lights and see a Palmetto Bug. My theory is that it may have crawled on you while you were asleep but also that you may have become subconsciously aware of its presence by some sort high or low pitched noise that it makes beyond the normal range of hearing. So my question is do Palmetto Bugs produce such a sound which might subconsciously alert you to there presence? Clem 13:50, 21 August 2007 (UTC)

Are you asking if cockroaches are psychically telling you that you need to put the garbage out? Capuchin 14:08, 21 August 2007 (UTC)

No, although the last consultant bill they sent me was way to high for me!...;D

No, what I am asking is if Palmetto Buds, in particular, make any kind of sound that might alert you to their presence but which is below or beyond normally audible hearing. Clem 14:20, 21 August 2007 (UTC)

Like crickets, only inaudible. Clem 18:25, 21 August 2007 (UTC)

telescope design

on all telescopes using mirrors you have to have a small mirror at the focal point to reflect the image to where your detector is. but off course having the small in the way of the big mirror means that a) you have a small area that's unusable on the big mirror and you would get diffraction happening round the small mirror's support struts.

why is it then that astronomers don't just angle the main mirror so that its focus is no longer between it and the stars ie it focus of to one side (like making a telescope a V shape with the main mirror at the intersection of the two sides) surely this would allow better images to be formed as you can use all of the mirror and you wont have diffraction problems? is it that either its not much of a problem or does my idea cause more problems then it solves?--Colsmeghead 14:35, 21 August 2007 (UTC)

The size of the central obstruction caused by the secondary mirror is pretty tiny relative to the total area of the primary mirror, so the answer usually boils down to 'it's not worth the hassle'. Mounting the secondary mirror off-axis would add a great deal to the size, complexity, and cost of the telescope and its mounting; it's also likely to add unusual asymmetric distortions that would bug the hell out of scientists trying to do anything quantitative with the instrument.

Worse still, the shape of the primary mirror would not be a nice simple surface of rotation. In order to move the focal point off-axis, the mirror would have to have a complex shape. This increases the cost of manufacturing, and also increases the likelihood of errors. TenOfAllTrades(talk) 15:00, 21 August 2007 (UTC)

Actually, there are such telescopes - they are called Schiefspieglers, and most follow a design published by Anton Kutter in 1958. There is an overview here, construction drawings here, a picture here and a copy of Kutter's original article here. The design appears to be mainly used by amateurs, so I imagine that, as Ten says, the problems outweigh the benefits for professional use. Gandalf61 15:30, 21 August 2007 (UTC)

Those are some great links. The third link above seems to summarize the problem with using a Shiefspiegler design for large instrument:

"The tilt of the primary mirror...induces significant image errors (astigmatism and coma) in the central part of the image (and even more off-axis).

A defined tilt of the secondary mirror...can produce the same image errors with opposite sign and allows for its compensation.

Unfortunately, these errors can not be compensated completely, because the optical design owns not enough degrees of freedom. The image errors can be minimised by realising Schiefspieglers with small apertures and low f-ratios (smaller than about f/18)."

In other words, the flaws of the instrument are minimized if you make it very long and with a small aperture—exactly the sort of things you don't want to have to do when you're trying to construct a large telescope. That article also describes a system that gets around most of the aberration by using a three-mirror system, but that has the drawback of involving four reflections (loss of light, introduction of distortion) and requires two large mirrors. I can see where they would fill an interesting niche for hobbyists, though. TenOfAllTrades(talk) 19:07, 21 August 2007 (UTC)

Plus, astronomers love those cool little starbursts caused by the struts. --Sean 17:42, 21 August 2007 (UTC)

Hyperventilation

In American films and TV programmes, one often sees characters hyperventilating and being given a paper-bag to breathe into. However, I have never (in real life) heard of anyone actually hyperventilating. Is it more common in the USA than in Britain? DuncanHill 14:47, 21 August 2007 (UTC)

I suspect the the film industry – as they usually do – have taken a not-particularly-common disorder and enjoy overusing it as a plot device for comic or dramatic effect. You may be shocked to discover that American film and TV writers are sometimes prone to laziness and will resort to stock clichés in lieu of actual research or creative writing.

From this link, hyperventilation syndrome (HVS) may affect up to 6% of the general population. (But of course one should take that 'up to' with a hefty grain of salt.) Acute hyperventilation (the panicking, breathe-into-a-paper-bag, tingling, possible-loss-of-consciousness, saw-it-on-television sort) has a fairly low incidence. It represents only about 1% of total HVS cases. Unless you're a physician, you'll probably never run into an acute HVS case. TenOfAllTrades(talk) 15:12, 21 August 2007 (UTC)

Thank you, I had suspected something of the sort. DuncanHill 15:15, 21 August 2007 (UTC)

I particularly enjoyed this part of your excellent link -

Prehospital Care:

Because respiratory distress or chest pain has many potentially serious causes, this diagnosis should never be made in the field. Even when a patient carries a prior diagnosis of HVS, transporting patients with these complaints for a more complete evaluation than is available in the field is prudent. Rebreathing into a paper bag is not recommended in the field. Rebreathing should not be initiated in the ED until after more serious etiologies have been excluded. Deaths have occurred in patients with acute myocardial infarction (MI), pneumothorax, or pulmonary embolism misdiagnosed as HVS and treated with paper bag rebreathing.

So lazy scriptwriters may be killing people! DuncanHill 15:20, 21 August 2007 (UTC)

Indeed, I have often wondered if dangerous misleading of people shouldn't be punishable ("There should be a law against it!" :) ). How often does one see someone in a film crash a car and walk out merely in a daze? Even a crash at low speed (by car standards) is easily lethal, even when wearing a seatbelt. The misconceptions based on that lie are bound to have cost thousands of lives (considering over 30 million people have died in car crashes). Ironically US movies are chuck full of warnings against smoking but promote unsafe driving, which is much more lethal (and to other people to boot). DirkvdM 18:53, 21 August 2007 (UTC)

DNA

Every human being has DNA that is completely (100%) distinguishable from any other human being. The only exception is twins (or triplets, etc.), who have the same DNA. So, first of all ... is my understanding correct so far? If so, when you take the case of twins ... is there any way whatsoever to distinguish their DNA or is the DNA a 100% match such that it is completely impossible to ever distinguish? Also, does this hold for all twins (identical and fraternal), or just the identical ones? Thanks. (Joseph A. Spadaro 17:10, 21 August 2007 (UTC))

Fraternal (dizygotic) twins share as much genetic material as between any two siblings of the same mother and father, they're just carried in the same womb. Apart from any mutations that occur after the zygote divides into the two fetuses, identical (monozygotic) twins have identical DNA. Fraternal twins have a higher likelihood of having identifiably different DNA than identical twins. It'd be difficult to distinguish identical twins by DNA alone, because they're essentially clones. However, they'll have different fingerprints and other characteristics defined by the environment. -- JSBillings 17:41, 21 August 2007 (UTC)

unidentified bird, mammal, insect

Hi. Recently I saw a bird on a power line. It was an estimated 2 in tall, and yellow. Its call, if I remember correctly, was a high-pitched chirp. Recently I saw this mammal. It looked almost exactly like a black squirrel. However, it was apparently much smaller, and its tail was so small that it was barely distinguishable. Finally, I saw this insect. It was light milky brownish-yellow, and about half a millimeter long. It typically is seen on old paper or wood. Can someone help identify these animals? If it helps, I live in southern Ontario. Thanks. ~AH1^(TCU) 17:30, 21 August 2007 (UTC)

The insect sounds like a termite. -- Kainaw^(what?) 17:38, 21 August 2007 (UTC)

The bird could be an American Goldfinch, although they're a bit bigger that 2 in. -- Flyguy649 ^talk _contribs 19:15, 21 August 2007 (UTC)

Conjoined twins

What if, by chance, one conjoined twin committed murder. However the other twin tried, in all possible ways, to prevent this from happening. How will the murderous twin be judged? I mean, you can't sentence one to death/life in prison while the other is innocent. Another question is what if one female twin decides that she wants consensual sex with a man but the other twin (assuming they are joined at the waist) refuses this to happen. Can that twin charge that man for rape? --WonderFran 18:30, 21 August 2007 (UTC)

It's an interesting question although as far as I know, one that has remained hypothetical only. There's at least one film [25] on the subject, and quite a bit of discussion of the topic easily accessed via google. Donald Hosek 18:47, 21 August 2007 (UTC)

Note: a civilised society doesn't have the death penalty in the first place and life sentence only in very extreme cases. So that softens the dilemma a bit, but doesn't make it go away. One could of course make an exception for such an exceptional case. Have there ever been any such cases? I suppose a different kind of punishment could be devised. An interesting idea would be to have them separated (if the other twin gives their consent). Now this often comes with a risk, but one could decide to do it in such a way that the other twin is in no danger and the criminal twin takes all the risk. If the operation is successful, then the offender can be punished as a separate(d) person. Of course then a new problem arises - can a medical treatment that entails a risk be forced on someone in the course of a punishment? Consider this: suppose a wrongdoer is so unfit for prison life that imprisonment would almost certainly have a seriously damaging psychological effect on them (which must happen quite often). Well, they should have thought of that beforehand, shouldn't they? Maybe some people are too stupid to realise the consequences, but can that ever be an excuse in a court?

Linguistic note about the second question: if she want sex it's necessarily consensual, so that was a tautology. :) Also, why should it be a she? DirkvdM 19:11, 21 August 2007 (UTC)

Well of course WP has the plot summary of Chained for Life that Donald Hosek refers to above. - hydnjo talk 19:20, 21 August 2007 (UTC)

Dirkvd - your agrument contains so many tangents that it hardly answers the questions let alone make sense. It is known that there have been rare cases where a female has raped a male however difficult it be so. To make things "easier" I chose female twins than male. I threw in "consensual" for legal sake. You can want sex when your drunk and not remember the next day. But in legal jargon, consensual means consensual.... --WonderFran 19:30, 21 August 2007 (UTC)