okay i now this is homework but if some1 could point to the right topic then i can do the rest. I've done an experiment with x ray diffraction which were told the x-rays are at 2 frequency's and was wondering what an appropriate error in the wavelength would be. i can think to sources of error in the wavelength but i don't now how to quantify it. the two i thought of where the sources not quite emitting at the wavelength said, and the wave spreading between source and the crystal (ie wavelength L ends up being several waves over L-delta L and L+delta L, i assume we used soft xrays though not sure if that helps or is true wavelengths given where around 0.1-0.2nm
okay i now this is homework but if some1 could point to the right topic then i can do the rest. I've done an experiment with x ray diffraction which were told the x-rays are at 2 frequency's and was wondering what an appropriate error in the wavelength would be. i can think to sources of error in the wavelength but i don't now how to quantify it. the two i thought of where the sources not quite emitting at the wavelength said, and the wave spreading between source and the crystal (ie wavelength L ends up being several waves over L-delta L and L+delta L, i assume we used soft xrays though not sure if that helps or is true wavelengths given where around 0.1-0.2nm--[[User:137.205.79.218|137.205.79.218]] 23:53, 13 February 2007 (UTC)
Search first. It's quicker, because you can find the answer in our online encyclopedia instead of waiting for a volunteer to respond. Search Wikipedia using the searchbox. A web search could help too. Common questions about Wikipedia itself, such as how to cite Wikipedia and who owns Wikipedia, are answered in Wikipedia:FAQ.
Sign your question. Type ~~~~ at its end.
Be specific. Explain your question in detail if necessary, addressing exactly what you'd like answered. For information that changes from country to country (or from state to state), such as legal, fiscal or institutional matters, please specify the jurisdiction you're interested in.
Include both a title and a question. The title (top box) should specify the topic of your question. The complete details should be in the bottom box.
Do your own homework. If you need help with a specific part or concept of your homework, feel free to ask, but please don't post entire homework questions and expect us to give you the answers.
Be patient. Questions are answered by other users, and a user who can answer may not be reading the page immediately. A complete answer to your question may be developed over a period of up to seven days.
Do not include your e-mail address. Questions aren't normally answered by e-mail. Be aware that the content on Wikipedia is extensively copied to many websites; making your e-mail address public here may make it very public throughout the Internet.
Edit your question for more discussion. Click the [edit] link on right side of its header line. Please do not start multiple sections about the same topic.
Archived questions If you cannot find your question on the reference desks, please see the Archives.
Unanswered questions If you find that your question has been archived before being answered, you may copy your question from the Archives into a new section on the reference desk.
Do not request medical or legal advice. Ask a doctor or lawyer instead.
The reference desk is not a soapbox. Please avoid debating about politics, religion, or other sensitive issues.
February 9
Hottest Temp...
Amigo of mine said that it hasnt been above 100 Farenhiet in the U.S. in February of '07, is this true? I just read a NASA article that said Death Valley, CA, USA is the hottest place on the Earth...for real?
Since it's barely a week into February, and February being in the winter, I highly doubt the U.S. has had areas reaching 100 F, which is already not too common during the summer. But yes, I believe Death Valley is the hottest place on earth. --Wirbelwindヴィルヴェルヴィント (talk) 02:11, 9 February 2007 (UTC)[reply]
The Atacama Desert in Chile is the hottest desert in the world, Death Valley is the hottest in the United States and El Aziza is where the hottest temperature was ever recorded (some say Aswan), the top spots for that are all in the Sahara somewhere. [Mαc Δαvιs]X (How's my driving?) ❖ 04:33, 9 February 2007 (UTC)[reply]
also check out Marble Bar, claimed to be the hottest town. It is located in Australia. But the most extreme here is 119.8F. Its consistently hot for months at a time. GB06:24, 9 February 2007 (UTC)[reply]
Sound coming from tv to computer speakers
I've noticed that sometimes when I put my hand against my tv screen, which is right by my computer speakers, a sound comes out of my computer speakers. They aren't hooked up in any way so I was wondering how this could be. Thanks. Imaninjapiratetalk to me02:22, 9 February 2007 (UTC)[reply]
My guess is that you get a lot of static 'sparkles' when you put your hand on a CRT screen in dry humidity. This could be picked up by the speaker wires, especially those amplifying ones, that are powered on, but not connected directly to a computer. --Zeizmic02:51, 9 February 2007 (UTC)[reply]
Pressure treated lumber splinter under the skin...?
I know that pressure treated lumber has arsenic and copper compounds, etc. to prevent insects from attacking the wood. So what happens if one gets a splinter when carrying pressure treated lumber? Is there enough toxic chemicals in a splinter if left under the skin to get into the blood stream and cause death? -- Barringa03:32, 9 February 2007 (UTC)[reply]
Not cause death, no. If the preservatives were that toxic to humans, you wouldn't be able to buy the wood just anywhere, and you wouldn't carry it bare-handed ever, and you wouldn't build decks out of it that you would then walk on barefoot or casually eat spilled hamburgers off of.
With that said, though, the chemicals are pretty nasty. I've noticed that if I saw pressure-treated wood, I feel a raspy sensation in my throat that I certainly don't get when sawing regular wood. (Yes, I should probably wear a dust mask more often.)
I don't think I've heard of splinters from treated wood being hazardous. (If anything the chemicals might help kill the germs that might otherwise infect the puncture wound.) But I'd certainly pay extra attention to a nasty puncture from treated lumber, and seek medical attention if my skin turned a funny color or anything. —Steve Summit (talk) 03:49, 9 February 2007 (UTC)[reply]
Wikipedia is not qualified to give medical advice - this includes diagnosing if you are at risk from a given amount of a potentially dangerous compound. Wikipedia:Medical disclaimer. Usually, most locations have a free poison control hotline for things which aren't quite 9-1-1 emergencies. Failing that, you would do well to call your doctor's office or HMO, and speak with a nurse there. -- 20:46, 10 February 2007 (UTC)
Hello, I think I have stumbled upon an absurd situation at this article. I have tried to place a tag alerting editors that content policies may not be followed there. There is original research, and non-objectivity. For example, the article divides points of view into "paranormal" and "non-paranormal." The scientific point of view is referred to as "non-paranormal," rather than scientific. Also, scientists are referred to as "skeptics," rather than scientists, as if believing in extraterrestrials communicating via magnetic tape were the majority viewpoint, and there were some minority "skeptics." I believe it is the other way around, there is a minority which believes in this, and the scientific majority does not. Scientists are scientists, not skeptics and non-paranormals. Also, the article contains a self-published purported recording of a paranormal voice, which is original research, I believe, since it was recorded and published on a website by the same people, not by a reliable third party. an editor keeps removing the tag I have placed. I am not sure what to do.-MsHyde05:12, 9 February 2007 (UTC)[reply]
Yikes. At least posting it here will get more eyes on it, and hopefully that will help build a majority consensus. Nimur05:19, 9 February 2007 (UTC)[reply]
I've read through the article. They make very few falsifiable claims, so I don't know if you can truly cite them on inaccuracy (though it's certainly not a science article). I guess it's difficult to accept, but people will believe what they wish to believe. In its present form, the article clearly states that there are alternative, simpler explanations than the "supernatural" - but if people choose to conclude otherwise, no amount of proof can convince them. Nimur05:28, 9 February 2007 (UTC)[reply]
It's fascinating how one paranormal wiki-page can lead me onto a goose chase of paranormal stuff. If EVP infuriates you, check out Shadow people - there's all KINDS of awful science there! Anyway, it looks like there's some consistency among these pages. They all list Paranormal vs. Non-Paranormal explanations. Honestly, I'm content with that level of consistency. Though you and I may choose to believe the scientific explanation, assume good faith and let people think what they will. It doesn't harm us to allow them to live in ignorance. Plus it makes for entertaining television. Nimur05:33, 9 February 2007 (UTC)[reply]
Yes, but this is an encyclopedia. Neutrality is important. The original research policy looks like it was developed precisely to keep crackpot theories in check. That is fine if people want to privately believe that science is "non paranormal," but it is not appropriate to label it that. The majority definition of science is science, not "non paranormal." And the audio recording is, frankly, ridiculous. It was published on a website by the same people who recorded it. It could be a recording of their vacuum cleaner.-MsHyde06:33, 9 February 2007 (UTC)[reply]
The original research policy also keeps you from using your own beliefs to determine the validity of an article. However bunk EVP may be, it is notable. The article, in its current state, makes no claims as to its validity, and nothing about the article is the least bit against Wikipedia's policies. Furthermore, just to cover the complaints, skeptics is a perfectly appropriate term. By definition, those who do not believe in something are skeptical of it. Finally, the audio recording is also fine. Regardless of how valid it may be, it is still an example of EVP. – Someguy0830 (T | C) 06:41, 9 February 2007 (UTC)[reply]
It is claimed to be an example of EVP, but not by a reliable source. It is the original research of two people who make money off of EVP, and self-published it on their website. Skeptics is not the appropraite term for scientists. Per due weight, even in an article about something, an extreme minority view should be represented as such. That means, science is the majority view, not the "skeptical" view, or "non-paranormal" view. The article as written is heavily slanted towards the view that EVP exists.-MsHyde08:38, 9 February 2007 (UTC)[reply]
It is not. The thing is a blow by blow history and a possible causes section, with equal weight given to both. The article does not exist to disprove or prove EVP. It only exists to detail the phenomenon. – Someguy0830 (T | C) 09:08, 9 February 2007 (UTC)[reply]
I haven't read the EVP article (if for no other reason than that I don't have time this morning for "wild goose chase of paranormal stuff", as Nimur so nicely put it), but I'm prepared to believe that the article needs work. Thanks, MsHyde, for trying to do something about it. With that said, this Reference Desk probably isn't the best place to figure out how to better apply Wikipedia's NPOV policy to that article -- I'd also try its talk page and the Village Pump. —Steve Summit (talk) 13:24, 9 February 2007 (UTC)[reply]
I see that the proponents from the AA-EVP are pushing POV in the article again, as they stand to gain credibility for the organization and its beliefs from a Wikipedia article that supports the existence of EVP. The content of the article has been carefully limited by AA-EVP proponents in order to "present the best face" to the public, e.g. the varied beliefs and practices of hundreds of independent "ghost hunters" with regard to EVP has been left out, and only scientific-sounding research has been left in. I admit that these are rather vague generalized complaints, so if you go to Arbcom, you'll need to cite specific text which you dispute and concrete reasons which back it up according to WP policy. --- LuckyLouie03:18, 10 February 2007 (UTC)[reply]
Any unpublished recording is definitely original research, and should not be considered as a source to support the claimed EVP. I could make a tape with mysterious voices on it very easily. To be used in an article, it would need to be published by a "reliaable source," and in a scientific dispute it should have been published in a respected peer reviewed journal. Questionable evidence should not be used to create a Wikipedia article which can then be cited as "proof" that the claims are valid. No home-made flying saucer photos, no personal diaries of time travel or UFO abduction, no claims that one had a dream forecasting some publicized disaster. No claims that one is Elvis's love child. No personal bigfoot sitings. No claims of having invented a miracle cancer cure or perpetual motion machine. Edison15:59, 9 February 2007 (UTC)[reply]
immune system
Hello, i was just wondering when "B cells" inside our body is trying to fight off "invader cells" and there are also body cells there aswell how the the "B cell" tell teh difference beetween teh two other cells?
I agree with Rockpocket that the articles linked to answer your question. However, they contain a lot of information if you know little about this beforehand, so here's a simplified version:
In most circumstances, it isn't the B-cells that tell the difference between self and non-self. It's the helper T cells. Both B and T cells have antigen-specific receptors that are generated randomly by somatic DNA recombination when the cells develop. One clone of T or B cells has one receptor, which recognizes one single antigen only. B cell receptors (≈immunoglobulin) can arise that recognize just about anything. T cell receptors, however, are designed to recognize major histocompatibility complex (MHC) molecules, which are cell surface molecules found on most cells of the body, and which always have a short peptide bound. The peptide is put there when the MHC molecule is assembled, before it goes to the cell membrane, and may be derived from either the degradation of one of the cell's own proteins, or from a virus, or from bacterial proteins that the cell has "eaten". Because of the random process that creates the receptors, auto-reactive receptors are generated both for T and B cells. Auto-reactive T cells, however, are eliminated in the thymus, and never reach maturity. The T cells that reach maturity are those that recognize your own MHC molecules, with a foreign peptide in them. Those B cells that happen to be reactive towards the same foreign protein as a given helper T cell clone, will have MHC molecules that are loaded with peptides derived from that foreign protein, because recycling of their B cell receptors ensures that some of the material is internalized, degraded, and displayed on their surface bound to MHC molecules. When a helper T cell encounters a B cell with the right combination of MHC molecules and peptides, it signals to the B cell that now is the time to launch an attack against the invader. --NorwegianBluetalk13:43, 9 February 2007 (UTC)[reply]
Welcome to Wikipedia. You can easily look up this topic yourself. Please see eutrophication. For future questions, try using the search box at the top left of the screen. It's much quicker, and you will probably find a clearer answer. If you still don't understand, add a further question below by clicking the "edit" button to the right of your question title. --Shantavira13:02, 9 February 2007 (UTC)[reply]
There is at least one "solution" that is worse than the problem. Several waterways in the Unites States that used to be eutrophied are now beautifully clear because of the accidental indroduction of the zebra mussel. -Arch dude02:11, 10 February 2007 (UTC)[reply]
Zebra mussels are problematic for a number of reasons. One is that they clog inflow pipes for power plants and water treatment plants. Since they are in the tubes, they are difficult to manage. Another problem is that they settle on hard substrates. In many North American soft-substrate lakes that means that they settle on, and overgrow, native mussels. Since native North American mussels are in a lot of trouble (and North America is a centre of diversity for Unionid mussels) there are major risks to zebra mussel introductions. Guettarda21:13, 10 February 2007 (UTC)[reply]
Heat Sink Formulae
Given the fin surface temperature of 68 degree Celsius and resistor temperature of 100 degree Celsius what would be the heat sink design?? This is in context of a convection cooled RF Load of 60W operating at 1 GHz frequency. What would be the fin height, no. of fins and cross sectional area of fin??? The base of the heat sink is at a temperature of 87 degree celsius?
Are you the same person who was asking this before? I suspect you're not going to get the precise, detailed answer you need here. You might want to try asking your instructor, or hiring a knowledgeable consultant, depending on the context of your problem. Good luck! —Steve Summit (talk) 13:28, 9 February 2007 (UTC)[reply]
Among other factors you'll need to consider: What fluid is the heat sink immersed in, at what temperature does the fluid enter the system, is the fluid freely convecting or being forced to flow, how much turbulence occurs at the heat sink fins/pins, etc.
Before didn't you say 600 watts? It would take a while to heat up say a gallon of oil or silicone fluid with 60 watts of heat. Engineers who miss decimal points tend to design things which do not function up to expectation. I seriously mean this. The bridge falls down or the plane crashes. I had a professor who would take half off an answer for an "oops error' on that ground. Again, seriously consider a cooling fan, and look at a space heater as a model. You must consider the ambient temperature and the air flow. Perhaps a fan could blow room air in at the bottom, so the fan is spared the heat, and the hot air come out at the top or side. You need to spare your cable and connectors from the heat. I still suggest a thermometer or thermocouple (with a design which will not be affected by the RF emission) to make sure the oil is not too hot, and a design which makes sure the resistor is not partially out of the oil. Transformers sometimes have a float switch inside ot a level indictor with a float, or in the old days, a sight glass like on a big coffee pot. You must also allow for the expansion of the oil, so you do not have a pressure buildup which ruptures the can. Detailed design goes beyoond what I or most people here have attempted. There are probably specialized programs to be used with graphical mathematical analysis programs for such heat flow calculations. Good luck. Edison15:50, 9 February 2007 (UTC)[reply]
Thanks... I had said 600 W before but my requirement got revised to 60W... The ambient temp. would be 35-40 degree celsius and the fluid would be at that temperature too. The heat sink isn't immersed in anything and I would like to know if a fan would be required to dissipate the heat. I am considering using a resistor of 15 W rating and design the heat sink such that the resistor can absorb 60 W and dissipate without the heatsink(case/body) getting heated up more that 35 degrees in addition to the ambient temp...
So if your heatsink is not immersed in anything, maybe you're trying to make a black body radiator instead? (air is a thing) :p Also, the requirement of a fan depends on the size of your heatsink, whose heat resistance must be lower than 0.58 °C/W, and probably lower to take into account of other resistance like junction between your resistor and things like that. --antilivedT | C | G06:42, 10 February 2007 (UTC)[reply]
Uranium refinement
According to the Uranium article, the production of uranium metal from uranium ore involves using uranium halides. Are there any simple ( but not necessary quick or efficient ) ways to produce uranium metal direct from ore ( such as using electrolysis or reducing agents ? Robmods11:17, 9 February 2007 (UTC)[reply]
The ore can be treated with nitric acid or sulphuric acid. Then treated with ammonia, producing ammonium diuranate. When heated in air you get U3O8 The metal can be made by roasting U3O8 with sugar charcoal in an electric furnace. But watch out as it burns at 180° C. There is no need to use halides in this process. The idea is to separate chromium and molybdenum from the mix. Probably UF6 is required to do isotope separation, as it is a gas at fairly low temperatures.
How many protons, neutrons and electrons is in the average in human body
Hallo, I´d need to know, how many protons, neutrons and electrons is on the average in human body? How many is it for one cell? Thank you
You can make a rough estimate from four assumptions.
Essentially all of the mass in your body comes from protons and neutrons (electrons are so light that their contribution is negligible for now; the masses of each particle are in the linked articles).
Your body will contain roughly equal numbers of protons and neutrons, as the most common elements and isotopes (oxygen-16 and carbon-12) in your body contain equal numbers of protons and neutrons. (For bonus points you can account for the contribution due to hydrogen, which mostly contains one proton and no neutrons; these tables have the relative contributions of each element to the body's weight: [1], [2]).
The number of electrons is equal to the number of protons—your body has no net charge.
Finally, the human body contains roughly 100 trillion cells: see Cell (biology).
I am aware that there are the four primary tissues- neural, connective, epithelial and muscle- and that most(all?) tissues fall under these, but where would specific tissues of the organ fit, say liver or kidney...
It depends. Most organs contain a mix of the four 'classical' tissue types. Taking the heart as an example, it contains:
Neural tissue: The heart is innervated by (among others) the vagus nerve.
What about say specific cells like hepatocytes, kupffer cells etc. Do they have to fit into the 'primary' tissue classification? (cells do make up the tissue after all- they only seem to fit into the connective tissue group...)
In the histological schematic you are talking about, hepatocytes are endothelial, they form sheets with clear lumina (is that the plural for lumen?); and kupffer cells are connective tissue (they are really just special macrophages). Remember that connective tissue falls into two categories, mobile (like plasma cells, mast cells etc.) and resident (fibroblasts, adipocytes, etc.). As stated above, these cell types interact metabolically and structurally to make the tissues we call organs. I can't personally think of any epithelial cells which appear without nearby connective tissue, nor muscle which occurs without neural tissue either connected (as with skeletal muscle) or somewhat nearby (though with the muscular conduction in the heart, cardiac tissue is something of an exception).tucker/rekcut22:51, 9 February 2007 (UTC)[reply]
Goldfish floating upside down
Ever since I got a couple of goldfish (the typical big-eyed kind that you can get in any pet store), one of them has spent a lot of time floating upside down at the top of the water. The first time I saw it do it, I thought it was dead. But a few minutes later it was swimming around fine. I've had it now for about six months and nearly every day it does this playing-dead upside down thing. Sometimes it even swims around the tank upside down for several minutes. Is this unusual behavior? Is my fish sick? Or is it just a weird fish? Deli nk15:31, 9 February 2007 (UTC)[reply]
FYI, you probably have comets; they're a very common kind of "fish store" goldfish. And yes, it's quite uncommon for a healthy fish to be completely inverted, although they certainly do momentary headstands, tailstands, and the like when feeding.
There seems to be quite a bit of info out there on swim bladder problems, as Guettarda suggested. After reading a bit, it's pretty clear that's the problem. Thanks all! Deli nk19:16, 9 February 2007 (UTC)[reply]
how much force does it take to propel a body the size of (lets make it easier: Pluto)
how much force to propel an object of this size???...or to change its current direction of motion??? and could humans ever achieve such a thing as propelling such large objects...??? how much does it take to fight the suns gravity and drive such a large object out of the solar system???...can the gravity of other planets be used to make it easier?? yet what would the initial force have to be like???...perhaps its easier to work with objects out near pluto???...could pluto and another object out that way be set into orbit around eachother on course heading out of the solar system???...(from a biologist)(its been a while since college physics class someone else can answer this quickly)...Benjiwolf19:10, 9 February 2007 (UTC)[reply]
F=ma, therefore the force needed to move an object would be the mass of the object, (in kg) multiplied by its acceleration, which is the same as the combined forces of gravity acting on it (in m/s^2):) Gravity varies with the square of distance from an object, so away from a planets surface, most of it would come from the sun:) Therefore it would decrese as you got further from the sun, but the masses and therefore gravities of other planets also needs to be considered:( So to find the forse you would have to work out the effect of gravity, and its direction, and then use this to find the force pulling the moon &c away from where you want it to go, and then multiply this by its mass:)Hidden secret 719:45, 9 February 2007 (UTC)[reply]
It's more relevant to talk about the energy that would be required to move a planetary satelite from its orbit. You cannot merely consider all the forces currently acting on a body (which are considerable in this case), but you also have to consider its momentum, which is enormous for something with planetary mass and velocity. Invoking purely classical methods would require enormous amounts of energy to significantly alter the course of something the size of, say, Earth's moon. There are a lot of specific questions that you pose, all of which would take a good bit of time to work through numerically. I'm not even entirely sure if you could do such a thing without invoking some general relativity (though you can almost certainly approximate it "well enough" with Newton's law of gravitation). -- mattb@ 2007-02-10T02:46Z
well thanks you two, i super appreciate it, good job, yet i did remember my force and gravity equations, my question was how much force (and is it possible) to move lets say "Pluto" (lets make it easier and more specific, and avoid planetary gravity influence on their moons, and the various methods that might utilize planetary gravity fields it may pass to advantage if timed correctly,... so we're just mainly dealing with the sun and minor/neglible gravity effect of other planets)...from what i understand people think we can knock an incoming asteroid off course with just a nuke or two...so my final question then is:...could we use the entire russian or american stockpile from 50 years of atomic reactors to "nudge" Pluto sending it out from the solar system???...(i figured this was more than a simple force equation, and i wasnt sure how nukes would play out in the equations and how they would be used to achieve their "effective force" relative to the total force held in the warhead) Benjiwolf14:16, 10 February 2007 (UTC)[reply]
Any amount of force will move the planet, it's merely a question of how much you wish to move it and how fast. Again, you're missing the subtle point that it's not as useful to talk about force as it is energy. You also need to specify something about direction. It would, for example, take far more energy to move pluto in a direction opposite to its momentum (its current direction) than it would to move it on a path towards the center of the sun (that is, in the same direction that the centripetal force of gravity acts). Your last question is very difficult to answer without some research, but my gut tells me that there isn't enough energy in all the nuclear bombs (nevermind practicality) to alter Pluto's orbit so significantly that it would "fly out" of the solar system within a short time frame. The energy released by a nuclear warhead is extremely puny on celestial scales. -- mattb@ 2007-02-10T19:01Z
OK..thanks again...my question wasnt exactly answered so i still have little idea as to this...yet perhaps in a million years we will be able to produce many degrees of magnitude greater the energy present in current nuke stockpiles and such a thing would indeed be achievable...moving a distant planet onto trajectory out of the solar system...its way better than a spaceship...and u can start adding all sorts of stuff to it to make it a real nice spaceship.......yet there are other ways to travel in style i think perhaps besides this...Benjiwolf19:50, 13 February 2007 (UTC)[reply]
Keeping raccoons alive
For my project at uni, we have to argue why we should keep raccoons alive as we are to debate with a group that says that they should be made extinct etc. Any help people?
You could start with the general arguments on why extinction of any species is bad. Then you explain what happened when the wolf was hunted to extinction in many parts of the world, and why it is being reintroduced. --Zeizmic20:56, 9 February 2007 (UTC)[reply]
I'm not sure if this would be what the moderator of the debate or whatever wanted, but costs versus benefits always works well; if you can show that it would be a lot cheaper to, for instance, buy everyone garbage cans secure against Racoon attack, than to exterminate them, then that is surely a point in your favour. --Neo21:04, 9 February 2007 (UTC)[reply]
More importantly: If you decide to keep them alive, but change your mind next year, you could deal with them then. But if you exterminate them now, and ever change your mind in the future, there would be no way to ever get a single living raccoon back. Extinction is forever. --mglg(talk)21:34, 9 February 2007 (UTC)[reply]
1)They are clever little animals with 2)impressive manual dexterity, 3) their skins make fine coonskin caps, 4)they are very delicious barbecued, 5)they could doubtless evolve to replace humans as he dominant species, and 6) they enable the sport of coon hunting. Those six reasons are sufficient to reject the proposition of making them extinct.Edison04:30, 10 February 2007 (UTC)[reply]
Not sure if I'm being helpful here but I'll try. Here are just a few of the arguments that you can anticipate the oposition will bring into play:
1)They are vectors of disease, raccoon rabies anyone?
2)They decimate populations of reptiles and birds by eating thier eggs. Here you could argue that thier numbers have only skyrocketed where we have eradicated the larger predators that would have "normally" kept thier numbers in check.
3)Extinction is a natural process. 99.9% of all the species that ever existed are now extinct.
4)They are members of a relatively small family of mammals so would hardly be missed.
5)The argument that a more genetically diverse population is necessarily a stronger population is a modern myth. So the loss of 1 more species would be insignificant.
I could easily pick apart any of the above arguments,as I'm sure you will. Good luck with the project.
Canis sylvaticus
Oops, I missed 1 that I shouldn't have.
6)Extinction need no longer be forever. given recent advances and anticipating those to come, we could put the genomes of Procyon lotor in a gene pool reserve should we ever find a reason to reinstall the species. Mea culpa. Canis sylvaticus
Some Biology Questions
Of the three types of RNA, which is the primary transcript of eukaryotic genes?
An image of a mitochondria is presented, and the question is what does it have in common with chloroplasts, the choices being DNA is present, ATP is produced, and Ribosome presence, or A and B, or all three?
A nucleotide may contain: Ribosomes, Nucleic Acid molecules, AMP, ADP, ATP?
How about telling us what you think the answer is and why so someone can see how/if your logic is wrong. Just being told the answer is no way to get an education... DMacks21:34, 9 February 2007 (UTC)[reply]
OK. #1 my response was mRNA, assuming that since they are limited-use, they would need transcription more often than re-usable ribosomal subunits and tRNA. The given answer was rRNA. #2, I knew both produced ATP, and I know both have their own DNA, I do not think either have ribosomes, so my answer was D: A and B. The Key said A, B, and C. #3, I put Nucleic Acid molecules, which is just plain wrong, but nucleotides don't contain any of those - AMP IS the Adenine nucleotide of RNA, so I suppose that was the reasoning, as that was the given answer on the key. ST47Talk21:56, 9 February 2007 (UTC)[reply]
1: see our articles on mRNA, tRNA, and rRNA. Yeah, seems like mRNA would be a reasonable answer assuming we're talking about nuclear genes. 2: visit the "structure" section of our pages about mitochondria and chloroplasts. That third question is pretty confusingly worded indeed. DMacks23:04, 9 February 2007 (UTC)[reply]
For part 3, If you look at the topic of nucleotide, can can see that AMPADP and ATP are nucleotides, and that a nucleotide contains a heterocyclic base a sugar and one or more phosphates. You could say that ATP contains AMP or ADP, or that ADP copntains AMP, so there are two possibles from that list. GB07:37, 10 February 2007 (UTC)[reply]
I believe the answer key is correct for all three questions.
1. The way i interpreted the question was which is transcribed the most, not which is transcribed the most often. Of all the RNA transcribed by a cell - i'd imagine rRNA would be the most (therefore the primary transcript). Simply because there is so much ribosomes in a cell and they all rely on rRNA to function, so therefore a hell lot of rRNA. Although mRNA may be transcribed more often (this also depends on what type of cell we're talking about), mRNA is also commonly broken down pretty quickly. Often, for a single mRNA, there are TONS and TONS of ribosomes (all with rRNA) translating it (see Polysomes). So it's like...for everything the cell transcribes, rRNA would be the most, hence the primary transcript.
2. Both mitochondria and chloroplasts defintely have their own ribosomes (prokaryotic ribosomes in fact, which supports the endosymbiosis theory). Those two organells divide on their own, and can produce their own proteins (although the host cell also supplies a lot). They both have DNA, they both have ribosomes, and they both (can) produce ATP
3. A nucleotide contains AMP. AMP is adenosine mono-phosphate - which consists of a adenine, a pentose sugar, and a phosphate group. In other words, the nucleotide with adenine is in fact a "adenosine mono-phosphate". But generally, when we're talking about nucleotides, we call it a "adenine nucleotide", and not "adenosine mono-phosphate". However, this is only for RNA. DNA has deoxyribose sugar and not ribose sugar.
The one-liner answer is "quantum mechanics". The energies of the photons (and thereby, their wavelength) emitted from an excited material are equal to the amount of energy lost by the electron transition that caused their creation. See spontaneous emission, atomic spectral line, and spectral line. Note that this process is also somewhat reversable, and one can characterize materials by the wavelengths of light they absorb (the basis of many forms of spectroscopy).
With respect to the flame test, I'd imagine that the characteristic color is produced from the many radiative transitions that occur when electrons excited by heat and the chemical reaction of oxidation change energy state in the correct manner. -- mattb@ 2007-02-10T19:27Z
To try and make this a little more lucid, let me explicitly point out that the particle energy profiles in different atoms and different combinations of atoms varies a good deal. -- mattb@ 2007-02-10T19:29Z
Why is that....?
1) When you take out earrings it feels like there's a little ball inside your earlobe?
2) What is the function of yawning and stretching - and why is it catchy?
3) What actually happens when you have 'pins and needles' or your leg is 'asleep'?
Thanking you,
San 23:18, 9 February 2007 (UTC)23:18, 9 February 2007 (UTC)23:18, 9 February 2007 (UTC)23:18, 9 February 2007 (UTC)23:18, 9 February 2007 (UTC)~
1) This is only a guess. It might be because you have become accustomed to having something in there, and when it is gone, it feels strange. In your case, like a small ball. − Twas Now ( talk • contribs • e-mail ) 02:43, 10 February 2007 (UTC)[reply]
If your ear is pierced, the scar tissue in the lobe feels like a ball. If they are not pierced, there is nothing there. Many guys who grew up in the 80's can do a comparison as they will have only the left ear pierced. --Kainaw(talk)05:26, 10 February 2007 (UTC)[reply]
It may not be just scar tissue. Collagen fibers form when soft tissue experiences shear, whether or not there's any scarring; the ball you feel may be like an internal callus.--Joel08:05, 10 February 2007 (UTC)[reply]
Why hasn't more attention been given to simply shielding the earth from sunlight? A series of thin, mirrored panels between the earth and sun would be more effective than trying to clear greenhouse gases from the atmosphere.
The costs for that would be huge, and it wouldn't really work since Earth rotates around itself and the Sun. Also, we'd lose so much of the visible sky that anyone involved in astronomy (that is, anyone who'd be involved in such a project) would reject the idea as preposterous. — Kieff | Talk00:33, 10 February 2007 (UTC)[reply]
You could always put the panels at the L1 Lagrange point; that would keep them fixed on the line between the Sun and the Earth. That said, it would be cheaper to just throw the panels into a low Earth orbit, and accept that for a bit more than half of each orbit they would be in the Earth's shadow and not providing any shade.
The decrease in sunlight would need to be fairly low; astronomers would only lose 1% of their sky, give or take. If you put the panels in a polar orbit, then only a very small part of the sky would be permanently hidden from sight.
Paul Crutzen (who won the 1995 Nobel prize in chemistry for his work on the ozone hole) has suggested the use of balloons or artillery shells to spread dust in the upper atmosphere; this would be an alternative way to increase the Earth's albedo and reflect more sunlight. He estimated the the cost at about $25 billion per year to maintain the dust level: [3]. TenOfAllTrades(talk) 02:32, 10 February 2007 (UTC)[reply]
(delayed due to an edit conflict) A cheaper way would be to spin basalt fibers from, e.g., moon rock, and weave fine gauze to diffract the light, rather than reflecting it. Large panels of this might be placed at L1 between the earth and the sun without too much loss of astronomical data, or ongoing thrust. With an oversized weave, they'd be more effective at diffracting IR radiation than visible light, minimizing the psychological effect. But it would still be insanely expensive, and control over the facility would be a nearly insoluble political problem, since it would enable a person to hold the world hostage.--Joel02:37, 10 February 2007 (UTC)[reply]
Dyson sphere contains a bit of discussion about just how huge an undertaking engineering something like this would be. -- mattb@ 2007-02-10T02:56Z
Too bad it isn't that easy to alter the global systems in a purposeful, systematic way. *rolleyes* It is really a stupid idea to try and do this in any way at current times. [Mαc Δαvιs]X (How's my driving?) ❖ 03:10, 10 February 2007 (UTC)[reply]
Becuase the the consequences of doing so could be infinitely worse. There are LOTS of questions about global warming including the natural vs. man-made element. The earth and sun both go through cyles that span millenia. Dinking with it using weather science that can't predict next weeks forecast would be extremely irresponsible. For example, the main component of greenhouse gases in the atmosphere is water vapor. When the earth heats up, more water is evaporated from the oceans into the atmosphere. This is a postive feedback cycle. More heat, more water evaporation. more heat trapped by greenhous gasses, more water evaporation, etc. BUT, water vapor forms clouds. These clouds refelect heat into space, cooling the atmosphere, which can't hold the water, reducing the greenhouse gases throgh rain. So which process wins or when does global warming get stopped by clouds? These are fundamental questions about the behavior of the atmosphere that needs to be answered before any radical steps are taking. Man using science to help nature doesn't have a very good track record. --Tbeatty05:20, 10 February 2007 (UTC)[reply]
Be fair. There's a world of difference between local weather and global climate. Actuaries can't tell you the date of your death, but they're good at saying what proportion of a given population will survive. Similarly, I don't expect that any of the climate models try to predict the cloud cover over a particular square mile on a particular day, but I imagine they're pretty good about global averages on a scale of decades.--Joel08:01, 10 February 2007 (UTC)[reply]
I am being fair since most of the "fix global warming now" ideas try to affect the locally temporal weather in an attempt to change the climate. Wouldn't it be a kick in the pants if the man-made solution to global warming actually made the summers hotter but the winters much colder? I dont't think anyone would think more hurricanes and more blizzards would be a good idea even if the it reduced the temperature by .3C on average over 100 years. Summers up 9 degrees, winters down 10. Great, global warming ended. It is essential that the local variation be predictable and not just the long term climate. Even short range actuarial prediction is awful. How many major hurricanse were predicted for the atlantic in 2006 using very sophisticated models? We didn't them to predict when or where, just how many over a 6 month period.
Climate models have been predicting warming since 1980 when the Global Cooling models failed. None of them have been accurate, though in terms of predicting temperature rise over 20 years. Also the models are currenlty conflicting about cloud cover as a climate forecast (not the idividual square mile forecast). They do not know how much global warming induced cloud cover will affect global warming. Tbeatty15:48, 10 February 2007 (UTC)[reply]
I'll give another example. I would like to see the global models predict the warming and cooling of the pre-industrial climate. It needs to be able to predict the multiple cycles (i.e. hundreds of year, decadal and millenial cycles of warming and cooling). It's very difficult because it depends on natural events (i.e. comets, volcanoes, sun cycles) that we currently cannot predict yet they are ongoing natural events. It may be that actuarily, comets hit the planet whenever the earth has warmed to this level, or volcanoes erupt, etc. It would defnintely suck to put up a permanent, irretrievable collection of mirrors the day before a major volcano eruption. Or a year, or 10 years before we saw the giant comet on a collision course.
Man has always thought he is more important and more influential in the universe than he actually is. That truth did not change with global warming. --Tbeatty15:48, 10 February 2007 (UTC)[reply]
See: Global dimming. There was a Nova program about it. -- 20:28, 10 February 2007 (UTC)
Why do things "inflate" when their velocity gets closer to the speed of light or "c"?
In Stephen Hawking's book "A breif history of time",
it says that as one has the velocity of 10% speed of light,it would be 0.5 times more it's normal mass
and as it approaches 90% ,it is at least 2 times more.
let it be negligible....but could you pls tell me , is it possible to trap the energy of ordinary light we get from our bulbs....also tell me is it possible to construct an artificial but long lasting circuit to trap the energy of visible light...Bhaskaran 8810:34, 10 February 2007 (UTC)[reply]
When you say "trap the energy of ordinary light", are you refering to things like solar panels? These can collect energy, but unfortunately, they are very uneffective (only about 10% of the energy which hits them is trapped". As for the inflation effect, it is a result of special relativity. For full info see Mass in special relativity, but in effect, because E=mc2, as E (the energy of the object) increases, m (the mass of the object) also has to increase to balance out the equation. Giving the object more energy by making it move faster also gives it more mass. Laïka15:56, 10 February 2007 (UTC)[reply]
Not entirely true. The best tandem solar cells to date have a conversion effiency around 31%. The best crystalline Si cells are pushing 25% effiency (pretty darn good considering that the theoretical maximum effiency for an Si quantum conversion PV cell is around 30%). Compared with other forms of electrical energy conversion, solar cells are pretty efficient. -- mattb@ 2007-02-10T18:43Z
trap the energy of visible light
let it be negligible....but could you pls tell me , is it possible to trap the energy of ordinary light we get from our bulbs....also tell me is it possible to construct an artificial but long lasting circuit to trap the energy of visible light...
This kind of device is called a solar cell. It is not 100% efficient, or very low cost, but it is useful in isolated or portable electrical items. This electricity can charge a battery. Most of a light bulb's energy comes out as heat rather than light. GB12:14, 10 February 2007 (UTC)[reply]
A black object will absorb energy from a light bulb. The absorbed energy will cause it to become hot. An "artificial but lonfg lasting sircuit to trap the energy of visible light" might be a black object surrounding a light bulb. Most of the electricity used by a light bulb is emitted as invisible infrared light at too long a wavelength to be seen. Edison07:25, 11 February 2007 (UTC)[reply]
Random junk.
here are a few sciency questions I don't understand. So i decided to put them all here and see if anyone else can understand. Some of them probably don't make any sense, but any help with those that do will be appreciated.
Why does helium float? What is it that makes it move upwards?
How much does helium weigh?
What is it that prevents a muscle from contracting when trying to move something that is too heavy?
Why does everyone look the same? Most people have two legs, two arms, one head &c, but DNA is just a list of proteins, so where does the rest of the information come from?
Why do things break if you drop them?
If a hollow ball could be made so that all of its surface was exactly the same thickness, and the pressure inside it increased, where would it break?
Why do the speakers on my computer make a noise when I touch the wire that should plug into the computer?
If I had a lump of iron, what would I have to do to turn it into a magnet?
How much could someone grow in one day before they ran out of all the chemicals they need to make more of themselves, and how fast could they grow if all their cells were dividing as fast as possible?
What happens to a birds feathers around its elbows and wrists when it folds up its wings? Shouldn't they get screwed up or damaged or something?
How much energy could someone respire to produce one litre of carbon dioxide?
If they kept eating, would they ever run out of the necessary nutrients?
I don't think feathers grow in such a pattern that this matters.
The average person breathes in about 500 mL per breath, and the average amount of CO2 in exhaled air is 4.5%, or 22.5 mL. This would take 44-45 breaths to do, and at a rate of 15 breaths per minute, this would take 3 minutes.
Might I suggest a collaborative effort for this question, since I think it will be clearer. I've copied Twas Now's answers below, with edits as I think they should be. Could other's improve them? Skittle18:02, 10 February 2007 (UTC)[reply]
Helium is less dense than air. It is the same reason rocks don't float.
Helium has an atomic mass of 4.002602 grams per mol. (Air has a mass of 28.97 g/mol) At atmospheric pressure, at 0oC, helium has a density of 0.1786 g/L, which means a litre weighs 0.1786 grams.
The muscle does contract, there simply is not enough force to move the thing!
All the information that make us look the same come from DNA. Proteins can do marvelous things!
When things fall, they convert their gravitational potential energy to kinetic energy (they go from being motionless high up, to moving quickly low down). When they hit the ground, that kinetic energy can't just vanish. It can be converted into a lot of things: sound energy, heat energy, kinetic energy in the other direction (if the thing bounces), deformation energy... That last is the thing that breaks or bends things. Another way of looking at it is to think of the object going from falling quickly to being still in a very short time. This means it has a large negative acceleration. From F=ma, you can see that the force on the object will be large, and that force can break it.
There is no way to tell. If it does actually break, the probability that it would break at any given point would be equal for all points on the ball.
If it was completely uniformly strong, it would break simultaneously at every point. In practice there will be thin or weak points that stretch more and fail first. A completely uniform material with no defects would be very strong - eg nested buckyballs, diamond, they could withstand pressures over 100 gigapascals (one million atmospheres). GB20:59, 10 February 2007 (UTC)[reply]
Sure, but the question was about it breaking from internal pressure alone. For which, Graeme's answer is right. --Anonymous, February 11, 23:51 (UTC).
I've wondered the same myself.
You may be putting a static discharge into the cable, you may be jostling a loose connection. There may be a piezoelectric effect in the cable insulator. It does not happen on my speaker cables! GB20:59, 10 February 2007 (UTC)[reply]
If they kept eating, would they ever run out of the necessary nutrients?
Feathers grow in cunning patterns that fold neatly into place when a bird folds its wings in the proper way.
The average person breathes in about 500 mL per breath, and the average amount of CO2 in exhaled air is 4.5%, or 22.5 mL. This would take 44-45 breaths to do, and at a rate of 15 breaths per minute, this would take 3 minutes. According to our article Respiration (physiology), aerobic respiration of glucose produces 6 moles of CO2 and 2830 kJ of energy for every mole of glucose used. Now CO2 has a density of 1.6 kg/L and each mole weighs about 44g. So there's about 36 moles of CO in a litre. This means about 16980 kJ produced for every litre of CO2 exhaled.
1. Helium floats up because the less dense want to be above. It's the same reason when you try to hold a balloon under water, the balloon wants to force itself up above water, because water is more dense than air.
It's not so much that what is less dense wants to be higher, but what is more dense wants to be lower. Gravity pulls everything down. But if it pulls a set volume (say 1 L) of helium down, it has to move 1L of air out of the way first. It's a lower energy situation to have the more massive thing lower, and the lighter thing higher, so that's what happens - the air goes down, and the helium is pushed upwards by the air coming downwards. See Buoyancy -- 20:16, 10 February 2007 (UTC)
7. There are electric signals in you, which is why EKGs work. I've been using an instrumentation amplifier, such as ones used for EKGs. Before we filtered noise, the output amplified signals changed significantly just from our hands being near, much less touching it. Using a multimeter, you can actually get a reading of how much resistance it is from hand to hand.
If you connect to an amplifier and speaker you get a popping sound as the nerves fire. The electrode has to be over a muscle - eg the thumb pad. GB20:59, 10 February 2007 (UTC)[reply]
9. I'm not sure about this one, but aren't there cases of cancer growing uncontrollably fast?
10. Correct me if I'm wrong, but feathers by the elbows and wrist fold in a way that it overlaps each other. Sort of like cards. You have your cards fanned out when you're playing, but they still fold up nicely into a deck afterwards.
I actually meant to ask how much helium weighed relative to the air arround it, and therefore how much weight a helium balloon &c could lift:) Apart from that I think I have all the answers I wanted, and more than I expected, thanks:) Also are you sure you didn't mean 16980J:?HS721:04, 10 February 2007 (UTC)[reply]
Okay, under ordinary temperature and pressure 1 mole of any gas occupies the same molar volume of 22.4 liters -- I'll say 22 liters to work in easier numbers. The molecular weight of helium is 4. Air is 21% oxygen (molecular weight 32), 78% nitrogen (mol.wt. 28), and 1% argon (mol.wt. 40) for an average mol.wt. of just about 29. So 22 liters of helium weighs 4 grams while the same volume of air weighs 29 grams. Therefore 22 liters of helium in a balloon will lift 29 - 4 = 25 grams. To lift 100 grams you need 22 × 4 = 88 liters, to lift 1 kg you need 880 liters. Of course the weight of the balloon itself must be deducted from the lift. Note incidentally that using the only available gas that's lighter than helium, namely hydrogen, does not improve the lift very much (and of course does create a significant fire hazard). 22 liters of hydrogen will lift 29 - 2 = 27 grams instead of the 29 - 4 = 25 grams for helium. --Anonymous, February 12, 2007, 00:00 (UTC).
We still haven't really answered #7. What sort of noise were you hearing when you touched the speaker wire? And were you touching just the wire itself, or the metal tip of the connector? And were these plain or amplified speakers?
I assume (since you said you were plugging them into your computer) that these are powered speakers, and I assume you were in fact touching the connector. But I'm not 100% sure what noise you heard.
If the noises were single clicks or pops, as other posters have suggested, they're likely static electricity discharges, or momentary flows of current due to the capacitance of your body. (Either some stored charge on your body is flowing into the speaker circuit, or an electrical potential in the speaker circuit is flowing into and charging you.)
But if -- as is more likely -- the noise was a continuous, low hum or buzz, that's the 60Hz (or 50Hz if you're in Europe) frequency of the AC electric power supply that's ubiquitous in the developed world. Electricity is everywhere, and your body acts as an antenna to pick it up. If your speakers are powered, their amplifier is sensitive enough to pick up the tiny amounts of radiated energy which your body is picking up, and amplify it so that it can be heard.
I just turned on my own speakers and touched the connector, and got a loud 60Hz buzz, just as I expected. (It was a no-brainer, as I hear that sound whenever I grab that connector to connect it to my iPod or computer.) Then I held my hand near the room lights, and the sound got louder. Then I held my hand near an outlet, and the sound changed. Then I touched the grounded metal screw on the outlet cover plate, and the sound diminished. (By grounding myself, more of the signal I was picking up drained into the ground, and was unavailable to the speakers.) Then I turned off the room lights, and the sound decreased quite a bit. Then I turned the lights back on, and played with the dimmer, and the sound changed some more. Because of the way they "chop" the AC sinewave, dimmers are notorious for injecting buzzing noises into inadequately shielded audio circuits.
If you have an oscilliscope handy, you can touch its input connector with your finger and see a nice 60Hz sine wave, confirming the above.
If you had some battery-powered speakers, and if you took them 'way out in the country, away from any human habitation, and as long as there wasn't a cross-country transmission line nearby, you might be able to touch the connector and get no buzz at all. —Steve Summit (talk) 22:30, 10 February 2007 (UTC)[reply]
Per 8) You could magnetize a lump of iron simply by hitting it with something hard while it was in the Earth's magnetic field or by placing it in a stronger magnetic field produced by a permanenet magnet or a coil of wire with DC current going through it. Edison07:20, 11 February 2007 (UTC)[reply]
Density of protein crystals
Attempting to answer a question on the reference desk of the Spanish wikipedia, led me into doing some calculations that left me rather confused. My a priori assumption was that the density of a crystalized protein would be somewhere in the vicinity of 1g/cm3. The PDB entry corresponding to human erythrocyte catalase, 1DGB, includes the following:
Question 1: Does this imply that one molecule of crystalline human erythrocyte catalase occupies the space corresponding to a cuboid with sides 83.5Å, 139.9Å and 227.9Å?
If the answer is yes, and if I'm not making some stupid error in my calculations, the molecule would occupy a volume of 2662131 cubic Ångströms, corresponding to 2.66 × 10-18 cm3. One mole of crystalline catalase would then occupy 2.66 x 10-18 cm3 × Avogadro's constant = 1597279 cm3, and given the fact that the molecular weight of catalase is approximately 250000 g/mol, the density of crystalline catalase should be approximately 250000 g/mol / 1597279 cm3/mol = 0.16 g/cm3.
Question 2: Where is the error?
Is my a priori assumption about the density wrong, is my understanding of a "unit cell" in the PDB wrong, or am I making some silly mistake in the calculations? --NorwegianBluetalk17:03, 10 February 2007 (UTC)[reply]
I had a look and I don't think you've made an error - the volume seems right. Is the molecular weight right? The explanation I'd come up with (if I too haven't made simple mistake) is that proteins typically contain a lot of space in between the chains - no matter how folded - this would give the low density.87.102.9.117 17:49, 10 February 2007 (UTC)
Consider the space filling model of the protein - there are many places small molecules (such as water) could go - so the structure is far from close packed - hence the lower density than say water or diamond..87.102.9.11717:51, 10 February 2007 (UTC)[reply]
Well, the problem is that the calculated density is only a sixth of what I expected it to be, but if that indeed is correct, your explanation would of course be plausible. My initial assumption about the density is based on
The density of the human body is approximately 1 g/cm3.
I expected the density of a crystallized protein to be approximately equal to that of a compact carbohydrate, since the atomic weights of carbon, nitrogen and oxygen are the same order of magnitude, and since carbohydrates and proteins have similar hydrogen content. Glucose is 1.54 g/cm3. Paper can be close to 1 g/cm3.
I agree it seems to low - here is something else - maybe the molecular mass is that only of the protein - I would expect considerable water of crystallisation in the crystal - bumping up the density.87.102.9.11720:00, 10 February 2007 (UTC)[reply]
By the way one possible explanation for a low figure is that the unit cell contains more than one enzyme unit - in different configurations - this would increase the density you calculated obviously.87.102.9.11719:14, 10 February 2007 (UTC)[reply]
Very true - 1DGB contains four peptide chains per asymmetric unit (Although the ~240 kDa figure appears to be for the tetramer). A much bigger reason for the error is that you have neglected to include the mass of the water in the asymmetric unit. Protein crystals aren't like salt crystals - they're more like set gelatin. Each protein molecule is surrounded by a large number of water molecules. If you look at the .pdb coordinate file for 1DGB, you'll see there are over 1000 water (HOH) molecules listed. This only includes those water molecules which are stationary enough to have significant electron density. There are many more which are too disordered to be seen distinctly. -- 20:00, 10 February 2007 (UTC)
It certainly would. How can one read what's in a unit cell from the PDB entry? The "space group" is listed as P212121. If that means that there are 8 molecules in a unit cell, we would have linear dimensions one half of those I gave above, and a density of 1.3 g/cm3. To me, that seems more reasonable. --NorwegianBluetalk19:56, 10 February 2007 (UTC)[reply]
That would be my guess too - but I'm not familar with the meanings of each space group - a separate question would confirm what the space group describes.87.102.9.11720:57, 10 February 2007 (UTC)[reply]
On checking it seems that the space group can have just one molecule per unit cell. If you wan't to ask about the space group the maths desk might be a good place to try as well..87.102.9.11721:01, 10 February 2007 (UTC)[reply]
effect of reversing real and imaginary components in the Schrodinger Wave Equation
In general if you change a + bi into b + ai the eigenvalue changes.. If a and b are parameters in the wavefunction. (There might be a wavefunction than doesn't change it's eigenvalue but in general the eigenvalue changes)
Hi, thanks very much for this. The reply is a useful one, and tells me something new, but I don't think I'm getting across precisely what I mean, perhaps because I don't have the background knowledge. I was referring to a wavefunction which is just in the form a + bi, not ea+ib. The values a and b would both be functions in themselves, rather than parameters, so I am not talking about any specific wavefunction, just all wavefunctions generally. Then, as I have understood it, the time-independent wavefunction depends on the amplitude of the wavefunction only, not the specific values of the real and imaginary components. This would mean that they could be interchanged without altering the probability at any part of the wave. The Mad Echidna22:48, 13 February 2007 (UTC)[reply]
Are personality disorders considered to be caused by the strictly environment one grows up in, and not genetic causes or brain damage? I remember suffering from Obsessive compulsive personality disorder ever since I was a child, though I can't think of anything that happened to me as a child that could have caused it.--70.244.121.8819:31, 10 February 2007 (UTC)[reply]
Outrigger Canoe
I am not sure if this question should be posted on this desk but here it is anyways. I have heard of people trying to circumnavigate the world in an outrigger canoe but has it ever been acomplished? Thank You for any answers.68.120.80.7619:44, 10 February 2007 (UTC)[reply]
MP3 player
Hi, I wasn't sure whether to put this on the Misc. help desk or this one, but I put it here anyway. I want to buy an MP3 player (not an Ipod). I've got two on my list to choose from so far.
Philips HDD6320 30GB for £100. Reviews on sites such as amazon seem to be a bit iffy: problems such as freezing and long gaps between songs
Archos Gmini XS 202s 20GB £110 - reviews seem to be good but the Archos page says that the produced goods are low quality.
I only have about 6GB worth of songs so far so capacity doesn't matter much. I want a bigger capacity so I can add more songs.
My Archos is an older model, but barring one issue with the line-in jack (which I don't use) it's survived four years, including my physically upgrading several components. Seems robust enough... Shimgray | talk | 14:59, 11 February 2007 (UTC)[reply]
It is easy to understand why time travel to the past would violate causality (grandfather paradox), why traditionally accelerating matter past the speed of light is impossible (infinite energy required, etc), but why does faster-than-light communication violate causality? (the question is not about why is it impossible with current technology) --V. Szabolcs21:07, 10 February 2007 (UTC)[reply]
From my point of view it doesn't - at least in terms of communication between two already known objects eg earth and moon. The info. would of course arrive earlier than expected based on a maximum speed of communication of 300,000,000m/s and that is all. (Are there any logically consistent references that state it does?)87.102.9.11721:17, 10 February 2007 (UTC)[reply]
(edit conflict) I'm saying that faster than light doesn't violate causality - it just violates any law that states that speeds faster than light are impossible.87.102.9.11721:34, 10 February 2007 (UTC)[reply]
Simple way to explain it: a FTL signal could potentially cause a communication to be received "before" it was sent. -- mattb@ 2007-02-10T21:20Z
Well, it depends. If the FTL communication can be done in a frame-independent way, then you can send a signal backwards in your own time frame. You do it by sending a message faster than light (in your frame) to a collaborator moving fast (but slower than light) relative to you. It gets there before you sent it, in his time coordinate. No problem yet. But then he can run the same trick and get a message to you before he sent it in your time coordinate. Now the message gets to you before you sent it, in your own time coordinate. So you could send yourself a message not to send it, and then we've got a problem.
Of course if it's not frame-independent -- that is, if there really is a preferred coordinate system, and we just can't discover it using slower-than-light stuff -- then we're OK. --Trovatore21:23, 10 February 2007 (UTC)[reply]
I don't think your example is quite right - suppose you have a pair of glasses that allow to percieve all things that move, even things moving faster than light - if that were possible..
So even at faster than light it takes time for the message to be sent, (if the message was in a bottle you could watch it going to your friend with 'faster than light' glasses), then you could watch the message being sent back (again using the 'faster than light glasses') this takes time too. So the returned message arrives after you sent it - albeit sooner than you could have expected with a limited speed of light. It doesn't arrive before.87.102.9.11721:30, 10 February 2007 (UTC)[reply]
In a standard euclidean 3d geometry with time constantly moving forward - it takes time for the thing to travel. I understand that relativity uses a different form of geometry - but if I ignore that - I find that at any speed it will be later on in my measure of time that the thing arrives. (I don't know if trying to look at it from the point of view of an observer who has a method of observation that is instantaneous (ie infinite speed) would help)87.102.9.11722:12, 10 February 2007 (UTC)[reply]
Sure, there are no violations of causality in Galilean spacetime. There's also no finite speed of light to move "faster than", so it's not relevant to the question at hand. Melchoir23:51, 10 February 2007 (UTC)[reply]
Lets say you send a message to me 2 times the speed of light. Because things going faster then the speed of light go 'back' in time, a conversation could run backwards. I send you 'Hi' and you get it 2 seconds before I type, so you send me back a message 'sup', and I get it 1 second before I originally sent 'hi', so I may not send it if you are already talking to me, violating causality--HoneymaneHeghlu meH QaQ jajvam09:30, 11 February 2007 (UTC)[reply]
If "things going faster then the speed of light go 'back' in time" then it's crystal clear why the violation occurs. But why does it happen in the first place? I've read a lot about relativity, but this seems to be a question I'm totally clueless in. Who said anything about traveling backwards in time? Are you talking about tachyons? As I understand, their behavior is caused by the mass being an imaginary number. But what about things without mass (or just with real mass) as information carrier? A part of deep space where the speed of light is larger than in vacuum? Wormholes? I know they are not proven to exist, but if they did, why would FTL information (not necessarily matter, and no tachyons please) travel backwards in time? --V. Szabolcs14:37, 11 February 2007 (UTC)[reply]
It has to do with the way coordinate changes work in relativity; events that are simltaneous in any particular reference frame are non-simltaneous in others, and in fact there's a reference frame where A occurs before B and vice versa. This is no problem as long as the two events aren't causally-connected (that is, information isn't sent from A to B). But if a signal is going from A to B (two points in spacetime) faster than the speed of light, then there exists a reference frame in which B occured before A, so the information is travelling back in time. To demonstrate this explicitly requires some math; it's explained, in probably over-technical language, in Special relativity#Causality and prohibition of motion faster than light. -- SCZenz14:50, 11 February 2007 (UTC)[reply]
SCZenz's answer is fine (though not quite complete; there's no immediate causality problem caused by a signal ending at a smaller time coordinate than the one it started -- it's just a coordinate, after all. You have to get the signal back to the originator before he sent it, to get the paradox.)
But I think Szabolcs and the anon have a good point. Information sent faster than light would not, for that reason, go backwards in time, in the frame of the sender. This is something a lot of science fiction gets very wrong. The fast-moving spaceship runs into some unexpected condition, it goes just a little faster, and all of a sudden all the clocks start running backwards. That's nonsense on so many levels. The paradox about what would happpen if you could send information faster than light (in a frame-independent way) is a serious one, but the garbled version that gets transmitted to the public is garbage. --Trovatore08:30, 12 February 2007 (UTC)[reply]
This is an impossible question. It's like asking: "If one plus two was six, what would that do to my bank balance" - the fact is that it's not six...so how can you answer? The equations relating to relativity produce results that math can't solve when you plug in a velocity that's faster than light. Look at something like the Lorentz transformation - it says that the amount of time/distance/mass distortion when things fly fast is: - OK - so let's make 'v' (the speed of our FTL thing be 1.1 times c...what happens to the math? Well, turns out to be 1.21 so the number inside the square root sign works out to be -0.21...soooo...the mass/length/time-distortion experienced by an object moving at 1.1c is the square root of a negative number. Would anyone like to tell me the square root of negative 0.21? Feel free to use a calculator! Yep - it's a complex number - what the heck would having a mass equal to the square root of negative 0.21 mean anyway? So this is a nonsense question - it's precisely as meaningful as "What would the world be like if 1+2=6"...it just isn't. SteveBaker00:05, 13 February 2007 (UTC)[reply]
No, that's way too facile. You can't prove something doesn't exist merely because our equations for describing other things would blow up if applied to them. Tachyons may in fact exist, and their having imaginary rest mass, if you can't bring them to rest, is not really a problem.
But, if we can communicate with them, and if they behave in a frame-independent way, then we have a problem, and this can be demonstrated without knowing anything at all about what tachyons are like in terms of mass or in terms of how they would experience time. --Trovatore00:16, 13 February 2007 (UTC)[reply]
Oh, to clarify: By "communicate with them", I mean "communicate, using them to transmit the message". I didn't mean "Hey there, Mr. Tachyon!". Hope no one was misled. --Trovatore01:07, 13 February 2007 (UTC)[reply]
The well known equations about relativity are only referring to object with mass, aren't they? What about waves? (I know it's still disputed whether light is wave, particle or both). This equation cannot give an answer for (yet undiscovered) places where the speed of light would be faster than in vacuum, or hypothetical methods transmitting information without mass involved. However, thank you all for the interesting answers :) So I must assume that ftl communication would only be possible if our understanding about the universe and our formulas based on that knowledge are either wrong or incomplete.. --V. Szabolcs16:50, 13 February 2007 (UTC)[reply]
Actually the argument is extremely robust; it doesn't depend at all on the details of how a message might be sent faster than light. It doesn't matter if the signal stays inside the universe or goes outside it, whether the particles/waves/whatever composing the signal satisfy conservation of mass or momentum, or even whether the signal is natural or supernatural. It could be carried by gods or demons or little green faeries and the argument would still apply.
The only thing you need to know is that you can send a signal to your collaborator, moving with respect to you, so that it arrives there (in your inertial coordinate system) faster than a photon would, and that he can send a message back so that it arrives to you (in his coordinate system) faster than a photon would. Well, let's make it "arbitrarily fast" rather than "faster than a photon", just to avoid some computations and inequalities. If you've got that, and if the unknown agency doesn't also alter the relationships between y'all's two coordinate systems, then you've got the paradox. --Trovatore18:19, 13 February 2007 (UTC)[reply]
If an artist carves a large design deep into the trunk of a living tree, does it harm the tree's health in any way? Is it harmless? Is it bad for the tree? Clearly this is fine to a dead tree, but I am concerned if it's bad for a living healthy tree.
For images of the specific type of carving I am asking about, please Google "colin partridge", and it's the first hit.
Yes I can affect the health of a tree - in the worst case (carving all the way round) in can sometimes cause the death of a tree (see girdling).
In many trees (not sure if all) growth takes place round the perimeter of the tree (trunk) just below the bark. - if this is removed then the tree will be damaged (stunted) on that side. I don't know the extent to which trees can recover from this.87.102.9.11723:13, 10 February 2007 (UTC)[reply]
Carving in the tree also makes the tree much more susceptible to all sorts of infections (insects, fungi, etc.) But it's likely that a tree would survive a small carving in the same way it usually survives branches breaking in storms and the like.
Carving a live tree wounds its living tissue. If the wound does not go through the bark, the tree can usually heal pretty easily, although there is a danger of infection if the cutting utensils are dirty. If the wound goes through the bark then the wood is exposed, creating a danger for fungal infections which can kill a tree. When branches are damaged there is a risk for infection. This is why you are supposed to prune branches flush with the trunk, so that the bark can grow over the cut surface, closing the wound. Since wood is dead tissue there is no way for a tree to defend itself against pathogens which have infected the wood, and no way to replace any tissues that have been lost. Guettarda05:08, 11 February 2007 (UTC)[reply]
Unless you're a tree-rights activist, I'd say don't worry about it. Cutting a design into a person's arm is damaging, but usually they don't die from it. Cut off a tree branch, it'll be just fine. It has to deal with all sorts of damages in nature, and it deals with them quite well I'd say, I bet if you look outside your window most places in the world you can see a tree. [Mαc Δαvιs]X (How's my driving?) ❖ 16:45, 11 February 2007 (UTC)[reply]
(1) Why is it that science "cannot approach" the supernatural? This is what I've usually heard and it's what the supernatural article says. But the ID people insist that the supernatural can be included in science, or that the accepted definitions used for "science" and "supernatural" are flawed.
(2) Is a claim like "The Bible is the fully inspired Word of God" inherently unverifiable by scientific methods?
(3) If so, is it because of an inherent philosophical difficulty, or simply because, in practice, there is no scientific proof for such a claim?
Science is a process, a way of thought. It insists that its truths be demonstrable, repeatable, and robust under doubt. It rejects any claims to faith -- other than perhaps faith in the scientific method itself.
But this means that science cannot "prove" any statement which requires, for its "proof", faith in one book that was written centuries ago, or trust in the unverified statements of lone observers who claim to have seen some otherwise inexplicable phenomenon.
Actually, science can begin to approach these subjects, in that it can go a pretty long ways towards disproving them. But (a) it can never utterly disprove them, and (b) lots of people are more interested in believing in these phenomena than in believing in cold, rational science. Furthermore, most scientists (with the exception of, say, Richard Dawkins), aren't interested in angering people by claiming to disprove their cherished beliefs. So there ends up being a pretty deep divide between scientific thought on one side, and religious and/or supernatural thought on the other. Each rejects the other's methods (in a nutshell, scientists reject faith, while dogmatists insist on it), so the schism remains. —Steve Summit (talk) 23:39, 10 February 2007 (UTC)[reply]
The above was a pretty good answer. I could recommend reading the first couple of lines of science whithout getting involved in explaining what is objective and what is subjective - I could quickly over-simplify to say that science is the study of things that are knowable and controllable.
Thus it's easy to scientifically study inanimate things such as rocks and the like - since we have no problem having control over them.
It's more difficult to study things that we have less control over such as other human beings (the science of behavour etc has difficulty coming to consistent conclusions..), fire (chaotic - difficult to understand), the atmosphere (difficult to predict the weather).
So in attempting to apply science to things that are inherently uncontrollable - such as supernatural phenonoma and powerful superntaural beings and gods then science falls down - it's simply not the right tool to apply for their study.
Matters such as religion and faith can be considered subjective (different people have different gods - some have none etc) - science is the wrong tool for the study of subjective knowledge - because it's a tool for the study of objective knowledge.
It is important to stress the fact that science CAN test some supernatural claims. If someone claims to have psychokinetic powers, you could just perform a controlled experiment to see if the person actually performs such a feat without tricks or other explanations. This has been attempted several times in the past, and not a single person has ever shown such abilities. The same can be said of telepathy and other extra-sensory perception claims, or even prayer. Not a single person or experiment has ever passed double-blind experiments, and if such powers or effects did exist they would be easily measured statistically. Since after extensive research there's no evidence supporting these claims, scientific community has labeled them as most probably false and wrong.
An interesting thing arises from these results. While the burden of proof lies on people who make those claims, and not on scientific community, people who support paranormal claims often challenge science to disprove them. This is not the way things should work, but it is a widely used strategy to make science look "powerless" against the paranormal, when it is the people who make the claims that should provide evidence to support them.
The magician and skeptic James Randi has even put ut the Million Dollar Challenge, encouraging people to provide evidence of the paranormal in return for 1 million dollars. Hundreds of people have been tested, and not a single one was ever able to prove their claims. — Kieff | Talk00:26, 11 February 2007 (UTC)[reply]
You can test "supernatural powers" like psychokinesis. But you can't test the hypothesis that "X was caused by the supernatural" because there is no way to separate causality. You can always argue that X was caused by a miracle. Some people argue that you can infer supernatural causation if you can show that the probability of something happening through natural causes is so unlikely that it's more likely to have been caused by the supernatural. However, that would only work if you had some way of assigning probability to supernatural events. But there is no way to assign probability to supernatural events, and this still doesn't rule out unknown natural causes.
The statement that "The Bible is the fully inspired Word of God" is unverifiable not only scientifically, but through any other methods as well (e.g., the bible does not claim to be "the fully inspired Word of God"). But it is impossible to test that assertion scientifically. For example, unlike the bible, the Qu'ran claims to be a direct revelation - however, there is no way to make a priori predictions of what divine revelation would look like, so there is no way to say whether something is significantly different from a divine revelation. Without some independent definition of what "divine revelation" should look like, there's nothing to compare the bible to. Guettarda05:01, 11 February 2007 (UTC)[reply]
The above post about ESP is opinion and not fact, many scientist claim that many experiments have shown evidence of psychokinesis and ESP. Robert Jahn, brian josphson, Fred Alan wolfe, and many others support the ESP hypothesis, the question has by no means been answered
— Preceding unsigned comment added by 80.6.35.89 (talk • contribs) 13:13, 11 February 2007 (UTC)[reply]
Well, no, the question has been answered, and that's not an opinion, it's as close to a fact as one gets in science. There are a few people who claim to be using mostly scientific methods and who claim to have found significantly suggestive results, but for whatever reason, their reports are not accepted by most of the rest of the scientific community.
Now, this brings up three interesting points:
Up above, I said that science insists on demonstrability, repeatability, and robustness under doubt. It also really, really likes -- and in many cases insists on -- some notion of mechanism. You can't just observe a repeatability; it's best if you can suggest why you think it's happening. In the case of ESP, you ought to suggest what pathway you think the "extrasensory" perception is traveling along, and what organ you think is mediating it. (Disclaimer: I'm no student of ESP, so I don't know to what extent its proponents are, in fact, attempting to suggest mechanisms.)
One might argue that the refusal by "the rest of the scientific community" to accept the various alleged positive results concerning ESP and psychokinesis is evidence of some kind of conspiracy. One might claim that science is, in some respects, just as closed-minded, knee-jerk, and faith-based as religion. And in fact, to some extent, these charges have some basis. Scientists are people, and people make mistakes, and get overly passionate -- sometimes to the extent of becoming prejudiced or dogmatic -- about their work. But I would also claim (with more than a little justification) that (a) closed-minded refusal to consider new ideas is counter to the ideal of science, (b) science is at least aware of its shortcomings and works assiduously (and with some success) to overcome them, and (c) any number of scientific revelations, now accepted as "fact", were in fact once brand-new and utterly heretical ideas.
There is a very interesting human phenomenon -- a subclass of our unfortunate tendency to fall into "us-versus-them" polarization -- which is the Underdog New Idea. That is, someone has a wonderful but heretical new idea, which because it's new and heretical there's a massive conspiracy by "the establishment" to ignore and suppress. Moreover, it's easy for that someone to get a certain number of ardent supporters, all of whom want very badly to believe that the conventional wisdom is wrong, and that their hero's new-and-different idea is deliciously Right. I don't know if this phenomenon has a name, but you see it all the time, and it's fascinating in its regularity. Citations welcome.
(1) Why is it that science "cannot approach" the supernatural? This is what I've usually heard and it's what the supernatural article says. But the ID people insist that the supernatural can be included in science, or that the accepted definitions used for "science" and "supernatural" are flawed.
This is a common misconception. A true scientist would say "if something termed as 'supernatural' were real, we could test it, and we do test it many many different ways. People have claimed to have supernatural abilities, or things, or live in supernatural places, or be supernatural, but nothing has stood up to 'truth testing' yet." James Randi is a great guy, in my opinion.
(2) Is a claim like "The Bible is the fully inspired Word of God" inherently unverifiable by scientific methods?
No! There's plenty of ways to prove that, or disprove it, but would a believe hear you if you disproved it? If you talked about the deaths over versions of the Bible, or the Roman Congress voting on what should be in it, or various Kings? I suppose it could have been inspired but is not still. We don't know what was written by human and... written by human with God's help, for this reason, I think it is already impure, because God himself did not write it, but use a human tool. So, the question if it is asking for inspiration, can be boiled down to "does God exist?"
(3) If so, is it because of an inherent philosophical difficulty, or simply because, in practice, there is no scientific proof for such a claim?
There is no scientific proof, however this does not necessarily deem it wrong. Lack of evidence found does not mean no evidence ever, but simply if there is no evidence for some claim, the skeptic has no reason to believe your claim. It is not wrong, because there is no evidence, just there is no reason to say it is right if there is no evidence saying it is right. If it is a binary situation, testing is somebody has psychokinetic powers or not, then evidence that he used physically induced air currents instead of psychically induced air currents, then that's usually taken as not only a negative, but a false positive. [Mαc Δαvιs]X (How's my driving?) ❖ 16:41, 11 February 2007 (UTC)[reply]
Why is it that science "cannot approach" the supernatural? This is what I've usually heard and it's what the supernatural article says. But the ID people insist that the supernatural can be included in science, or that the accepted definitions used for "science" and "supernatural" are flawed.
The difficulty here is that the word 'supernatural' is pretty much defined as "all of the things that some people believe but scientists have effectively disproven". After all, we don't regard (say) magnitism as supernatural. It's pretty weird - this invisible force that acts at a distance that most laymen have no clue about...but it's not supernatural because science has been able to produce repeatable experiments that show it happening. With stuff like human telepathy, not one single repeatable, controlled experiment has shown it happening - so we call it 'supernatural'. This definition of the word guarantees that science can never 'approach' the supernatural since we've said that the word means "things that science cannot approach". If we could see repeatable experiments, it wouldn't be supernatural anymore...it would be 'nature'.
Is a claim like "The Bible is the fully inspired Word of God" inherently unverifiable by scientific methods?
It's not that it's unverifiable - it's unfalsifiable - there is no possible experiment that could ever prove this to be false. This book was written by humans - that much is clear. Science would say that the complex interactions of their neurons and their environment caused this to happen. But since the existance of God is unfalsifiable - then it's impossible to prove that a supposedly omnipetant being who can do literally anything "by magic" didn't tweak those neurons - then cover his tracks so perfectly that science would be unable (even in principle) to find out that he was the 'inspiration'. We must resort to 'Occams Razor' (If there is a much simpler explanation - then that's what we're likely to believe) - and to Carl Sagan's mantra: "Extraordinary claims require extraordinary proof" - since (in scientific terms) this is a pretty astounding claim, the evidence to prove that it's true would have to be gold-plated and bullet-proof...and it's not. There is zero evidence. So overall - whilst science can't say for sure that it's bullshit - that's got to be our working hypothesis until/unless some evidence shows up.
If so, is it because of an inherent philosophical difficulty, or simply because, in practice, there is no scientific proof for such a claim?
It's worse than that. There is not even a possibility that there could be a proof that this 'God' thing is false. Any entity that is capable of literally anything with no limits whatsoever could fake evidence undetectably. So whilst in theory, the 'pro-God' community could prove his existance (eg By asking him if he'd just show up and do something really impressive and difficult) - any argument that science came up with (eg We've figured out exactly how the entire universe works - and we've got it down to this really simple and easy to understand equation - and there doesn't appear to be a God anywhere in the universe) can trivially be countered with "Ah - but God is infinitely powerful - he just made the universe come out that way to test our faith."...so it's a waste of time for science to try to disprove God - it's unfalsifiable. The problem with that is that there are an infinite number of unfalsifiable hypotheses: "The Invisible Pink Unicorn made everything and is infinitely powerful"...well, guess what? We can't falsify that either. "All of mankind are just software entities running inside The Matrix" - nope, no way to falsify that one either. "All I see of the world is through my senses - so I can't prove that my senses aren't fooling me - so maybe I'm the only being in the entire universe and everything I see is false"...there are an infinite number of these propositions. If science gave them any weight - then science would be useless to us. HUMANITY: "Hey Mr Scientist, how should I shape the wing of this airplane to make it fly more efficiently?" SCIENCE: "Sorry - we don't know because God may decide at any moment that he doesn't like airplanes so our equations are useless."...you see it's not very useful to include unfalsifiables into our thinking - it renders science useless. The fact that we always assume that unfalsifiable hypotheses are false is the only way for science to be of any use - and if it's not of any use - we shouldn't bother doing it. If you doubt that unfalsifiable theories get tossed out even though they MIGHT be true - just watch what's about to happen to String Theory. It fits the facts - it's workable - but it's unfalsifiable - and serious scientists who have realised that are running away from it. SteveBaker23:50, 12 February 2007 (UTC)[reply]
The supernatural tends to be anything that hasn't been proven by science:) There is a lot less of this now, so there is a lot less supernatural around, but still some:) And surely if god was omnipotent, he could stop scientists proving that he exists, and since they can't prove he does, does this mean he is stopping them, and therefore does exist:@Hidden secret 713:17, 13 February 2007 (UTC)[reply]
Cornstarch
Three Parts:
1-How is "modified cornstarch" made, including what, if any chemicals are used?
2-How is "high fructose corn syrup" made, including what, if any chemicals are used?
3-How is maltodextrin made from corn, including what, if any chemicals are used?
What are some examples of physical and chemical properties of Calcium Silicate?
I would like to know some examples of both the physical properties of calcium silicate and as well as some examples of the chemical properties of calcium silicate. Thank you so much.
I took a nice picture of a plant after some rain. Can the plant be identified by my picture, and if so, would it make an appropriate addition to that article? Thegreenj02:25, 11 February 2007 (UTC)[reply]
Hello. So i'm a highschooler in a physical world science class.
We are studying work (the force required to move something)
Basically i'm confused about this whole subject. does it have to do with gravity? how do we measure force?
Well I was assigned the investigative quesion "Would it require more work to pull a brick along a flat surface or an angled surface?"
If you could give me some info to help me find the answer it would be greately appreciated.
03:14, 11 February 2007 (UTC)03:14, 11 February 2007 (UTC)
It strikes me that the question as quoted is kinda hard to answer. Is it angled up or down? F'rinstance, if it were angled down by, say, 85 degrees, I doubt that very much work would have to be done. Bunthorne04:06, 11 February 2007 (UTC)[reply]
You can't force me to do your work for you. That being said, work is not force, it's force times distance; all else being the same, if you had to move something twice the distance, it would take twice the work. Gravity can be involved in work, but doesn't have to. For example, lifting a weight off the ground requires taking it into consideration. To answer your last question without answering your question, you should ask yourself how much force you would have to use to move that brick. Hint: what forces would oppose the motion? As a last resort, you could read mechanical work. Clarityfiend04:08, 11 February 2007 (UTC)[reply]
Start with Mechanical work. How mathematical is the class? Does it use vectors? The simple answer would be to look at the vectors that oppose movement. Gravity is a downward force. Friction is opposing force in the direction of movement. Tbeatty04:10, 11 February 2007 (UTC)[reply]
I think everyone else missed the meaning of your question:
A force is a push/pull that causes other things to move. The amount it effects things depends on that thing's mass - if you try using the same force against two different things, the thing with a small mass will be accelerated more than something with a big mass.
Work is a change in energy, which is also force times distance - which is not obvious at all, because it's usually not the same "work" we think of. For most high school physics classes, you're studying work from the viewpoint of a single force. For example, the total amount of work you do against(or get from) gravity is equal to the force of gravity times the distance you moved against(or with) gravity. Even though "holding a book up without moving it" would feel like "work", no total work is being done against gravity, so you probably would still consider it 0 work against gravity. Moving the thing side to side also isn't work - you're not moving it opposed to / with gravity.
So your "investigative question" is too vague - which work? Work against gravity? Work against friction? Note that gravity has a single direction, so the direction of your distance is important (you can only count the up-down distance for gravity). Friction acts in every direction that you might try to slide (as long as you don't lift off the surface), so the whole path's distance counts if you're calculating work by or against friction. —AySz88\^-^01:23, 12 February 2007 (UTC)[reply]
Way to confuse the poor kid! OK - so work is force times distance. So if you have to pull the weight twice as far - it's twice as much work. If you have to pull it with twice the amount of force then it's twice the work. OK - so now we know what work is. How about force? Well, there are lots of different forces. To get a block to move along a surface, you have to provide enough force to overcome friction and to overcome gravity and to actually accellerate the block. If the ramp is level - then gravity doesn't enter into the picture - so the forces you need depends only on the friction and however much accelleration you are giving it. In these kinds of school-level problems they probably assume that the block only has to move exceedingly slowly - so we can ignore the effort to accellerate it from a standstill (that would be F = m.a - force equals the mass times the amount of accelleration). For the sloping ramp, you also have to include gravity. If you are pulling the block down the ramp - gravity provides some of the force - and depending on how steep the slope is and how much friction there is, you may not need to provide much (or perhaps any) force yourself - at any rate, the force you need has got to be less than for the level ramp. If you are pulling the block up the ramp - then you've got both friction AND gravity to fight - so the forces you need is more than for the level ramp. If you are pulling the block over the same distance in all three cases then we know that the work required will be more for pulling the block uphill, less on a level ramp and less still on a downward ramp. This is good because it's exactly what you'd expect. If your job is hauling bricks around - you know it's less work to pull them downhill than uphill...I mean...DUH! In the real world - there are lots and lots of other annoying considerations - friction is generally less when something is moving than when it's stationary - that 'accelleration' cost isn't negligable - the amount of friction depends on the slope of the ramp - if the block moves. it's going to get hot - and that will change the nature of the frictional forces....all sorts of annoying practical details get in the way of knowing the utterly correct answer - but for school project the don't want that kind of depth. SteveBaker23:18, 12 February 2007 (UTC)[reply]
Grey Vs Gray
I would like to edit the heading for the 'Grey Matter' page; Grey should be spelt Gray as it is pertaining to a colour and not a family name. I have managed to edit all the 'greys'on the rest of the article but the title of the article as well as a diagram seem to be un-editable. How can I change it? Or can you change it please? Thank you.— Preceding unsigned comment added by 137.122.26.206 (talk • contribs)
So in just about every action movie ever made, some guy holds a gun to some guys head while guns are pointed at his own head. The premise of the conflict is that if the criminal is shot, even in the head, and even if he sees no sign beforehand, he'll have time to shoot his own victim before he dies. Is this at all realistic? Couldn't one of the poeple in this situation just pull the trigger without showing any sign beforehand and be certain he couldn't get shot back? I don't know which other desk might be better suited for this question.
70.108.199.13004:57, 11 February 2007 (UTC)[reply]
At point-blank range, the only way both people would end up dead is if they pulled their triggers at almost exactly the same instant. If one had already pulled the trigger, there would be no way for the other to get his off on time, unless the separation was only a few thousandths of a second after (or even shorter). − Twas Now ( talk • contribs • e-mail ) 05:40, 11 February 2007 (UTC)[reply]
I always thought it would cause them to simultaneously spasm some muscles, while collapsing. But, I confess to not having actually seen many people with guns be shot to the head. [Mαc Δαvιs]X (How's my driving?) ❖ 16:23, 11 February 2007 (UTC)[reply]
You don't necessarily die (or lose consciousness) instantly when shot by a gun, particularly with small calibers. In fact, people have taken bullets to their heads and walked around for hours afterwards. It all depends on the path the bullet travels. (The scene at the end of Fight Club, in other words, isn't entirely ridiculous.) That being said, I wouldn't want to depend on living long enough to fire the bullet. The situation is just a small-scale version of Mutual Assured Destruction, and movie-makers should be allowed some level of artistic license, no?
If that's not satisfying enough, I image one could do a few calculations. To find the answer, we would ultimately have to take various factors into account. The sound of the bullet travels at the speed of sound (350 m/s); bullets travel faster than sound, while in the air, but would slow down considerably upon hitting the skull. Then, one would have to take into account the time it takes for the brain to lose consciousness, and compare that to the time it takes to pull the trigger (which, considering that it would be a near-instinctual process, travels through nerves' electrical impulses - which is near the scale of the speed of light rather than the speed of sound). In short, I don't think it's crazy to imagine that if one person pulled the trigger in a movie's Mexican standoff, the person who pulled it would be at great risk of dying as well. zafiroblue05 | Talk22:07, 11 February 2007 (UTC)[reply]
I should have looked it up, you're right - except that rather than moving much slower than the speed of sound, action potentials move at around the same speed (100-1000 m/s, compared to sound's ~350 m/s) - so it's still up in the air. zafiroblue05 | Talk03:03, 13 February 2007 (UTC)[reply]
When the bullet hits someone in the head, the impact and the pain will throw him off balance for a short period of time, at least. This should give the victim some time to react -- WikiCheng | Talk05:25, 12 February 2007 (UTC)[reply]
Any info we provide about such topics is of course only for general interest and movie discussion, and is not intended to be practical advice for personal defense purposes. Wikipedia says simple reaction time is about 150 milliseconds for him to respond to the impact of the bullet or the sound of the shot by a trigger pull. (I have personally seen 100 msec simple reaction time). If the standoff participants are 10 feet apart, the bullet will travel ten feet in about 1/100 which is 10 msec. In the standoff described, if there were no possibility that the other gunman would agree to stand down, and he was going on like a movie badman about how he he was going to kill you right after he finishes his page of plot exposition dialogue, in other words you are completely sure he is eventually going to shoot you, and you have a sufficiently large caliber gun to completely mush his brain, I would shoot him through the brain and duck out of the way while emptying the gun at him. Negotiation is far preferable, but with his brain destroyed he cannot make an intentional trigger press, and odd are better any reflexive finger twitch depressing the trigger would fail to hit you than if he were allowed to fire a carefully aimed shot through your own brain. Of course you would say something to induce him to relax before you fired. Say "I'm giving you to the count of three to put down your gun. One.." (he relaxes), you shoot. You might also remark that he's going to have a hard time shooting you, because the safety on his gun is engaged (made you look). You would not want to give a visible "tell" that you were about to shoot. In other words, if you lose a lot at poker, being such a stone cold killer in the standoff is not going to work out for you. If it is not a standoff but just a person aiming a gun at another person, a judo instructor said that if the gunman is within easy reach, as is usual in movies and TV for composition and dramatic purposes, a trained martial arts fighter has a chance (but by no means a certainty) of grabbing the gun hand and sidestepping or turning so that when he pulls the trigger you are no longer in front of the gun. Then the martial arts expert can open the big can of whupass. But this requires a movement executed in the aforementioned 100 or 150 milliseconds, and even he said that he would not attempt his if it were a simple robbery. Just give him your watch and your wallet and don't wind up a dead hero. The average citizen would not succeed in the disarming attempt. A smart gunman would stay out of reach, and try to get his victim in an offbalance posture to prevent any sudden lunges (I guess that's why cops bark instructions for suspects to get in certain offbalance positions.) Edison17:54, 12 February 2007 (UTC)[reply]
It's pretty clear that the victim doesn't have time to react to the first person pulling the trigger - so the question initially boils down to: Will a bullet travelling through someone's head cause enough damage to prevent an almost instinctive pull of their trigger in retaliation? The fact is, we don't know. Nobody knows because you can't do experiments and there are vastly too many variables to make even an intelligent guess. However, lack of information doesn't necessarily stop this from being a viable scenario. Consider this: So there you are standing with your gun to his head and his gun to your head. You don't know for sure whether he would get a round off if you just pulled the trigger. However, you'd be taking an enormous risk. Furthermore, the other guy clearly thinks the same way - he's saying to himself "If I pull the trigger, there is a good chance I might die". If nobody has fired yet - then clearly both believe there is a big enough risk that if they shoot first they'll die. This is classic deterrence. You just have to provide a sufficiently credible probability of producing fatal retaliation for there to be a standoff. It doesn't matter what the facts of the matter are - only what the participants BELIEVE the probabilities might be. Since even a 1% chance of dying is pretty unacceptable to most people, we can see that this stand-off might actually be quite effective even if it's really unlikely that someone could pull the trigger with half of their brain splattered all over the floor. SteveBaker23:00, 12 February 2007 (UTC)[reply]
Great answer Steve!. I suppose this is what prevents the police sharpshooters from shooting the criminals even if they have a clean shot, if the criminal is pointing a gun to a victim's head -- WikiCheng | Talk10:29, 13 February 2007 (UTC)[reply]
There were a few other tests on missile buses for high altitude nuclear testing but none were on realistic trajectories (and I'm not sure if they were even in standard missile-warhead mating situations). The Soviets tested a number of ABMs in this fashion on realistic trajectories I believe but that's not the same thing as an ICBM at all. In any case this is the specific place on Wikipedia which discusses these tests. For a good book on the lacking of such testing see Inventing Accuracy by Donald MacKenzie. --24.147.86.18723:21, 12 February 2007 (UTC)[reply]
I am suffering from joint pains for a long time.Also I will be having muscle pulls easily.Sometimes, while playing cricket I had serious pain in my thumb and it will swell up and remain black for some days.What may be the probable reasons for my problems.
The blood is not impure, it is just low in oxygen when it is blue. Hemoglobin changes colour to red when oxygen is attached. Note that blood in some other animals is coloured differently, blue or violet or green even GB08:34, 11 February 2007 (UTC)[reply]
I remember reading that some women who are near crying babies sometimes start lactating. For example, wet nurses lactate but don't necessarily have babies at the time. --Wirbelwindヴィルヴェルヴィント (talk) 19:27, 11 February 2007 (UTC)[reply]
Hormonal abnormalities (a pituitary tumor) can cause lactation in women (or men). So it might happen. An unmarried girl might also be a new mother (it does happen). Edison17:23, 12 February 2007 (UTC)[reply]
Nothing is holding it still! All the loose objects in the Universe will be moving and spinning due to the way they were formed. Originally there was momentum or angular momemtum and the earth has retained momentum ever since. It has changed direction as it orbits the sun and galaxy.
There are several ways to answer this. The easiest is to say: "Gravity". The sun's gravity pulls the planets (including the earth) around in their orbits. But it's a bit more subtle than that. If the sun's gravity wasn't there, the planets would head off in straight lines and rapidly disperse all over the place. You might then still ask: "Why does the Earth Move" - but if there is no reference point to measure it's movement against, then for an object travelling in a straight line, you can't quite literally cannot say whether the object is moving such and such speed and in such and such direction - or whether it's standing still and all of the the other objects in the universe are moving in the opposite direction. So it's fairly meaningless to ask why or even if an object is moving in a straight line. Hence my earlier answer: Gravity is what bends those straight lines into the curves that make it clear that one object is moving relative to the other. SteveBaker22:43, 12 February 2007 (UTC)[reply]
According to Kepler the earth moves because the rays of light from the sun hit it in such a way that it is pushed sideways, but also moves round the sun instead of away due to huge magnets in both the sun and the earth:)Hidden secret 713:10, 13 February 2007 (UTC)[reply]
Casimir problem for weinberg
I recently heard about an arguement between two scientists about the level of energy in the Zero point energy field. Dr Steven Weinberg claimed that there was not all that much about, yet according to a recent page i read at physics web the zpf can produce pressure on casimir mirrors in the nanometre range [the least amount of energy between the plates] of about 1 atmopshere thats kgs per cm 2. Wouldnt it take a large amount of EM waves to produce this much pressure. The article isnt loading at the moment on my pc, but look the casimir effect page on this site at the link "casimir effect, a force from nothing" for the page about the 1 atmosphere of pressure.
I know what it is but the question still remains, pressures at the nanometre scale on the plates utilised in the casimir effect can reach up to the equivalent of one atmosphere of radiation pressure on the plates, this is because their is so little resistance inside the plates because much of the zpf is blocked out. My question to clarify is: How come, if steven weinburg is correct and the zpf is very weak, the pressures produced are that strong. surely it would have to be a hugely strong field to produce this kind of radiation pressure, even when there is nothing around to resist it. Please actually asnwer with something relevent to the question this time huh?
Causal observer
I would assume if you read the article, you would understand. The zero point energy is the lowest energy state an evacuated space can have. The Casimir effect, and the force being strong works only at the nanometer scale, because ZPF is so weak. It doesn't take much to move a mass so small, and it doesn't take much to push it hard. The Casimir effect happens because, sort of, the energy in the space outside the two plates is enough more than the energy in the space between the two plates. It takes the nanometer range to work, because it is so weak, such as the energy difference of between the plates and outside the plates, that needs to be high. [Mαc Δαvιs]X (How's my driving?) ❖ 17:22, 12 February 2007 (UTC)[reply]
Actually i think you may have misunderstood the article, From what i understand the casimir effect only works on the nano scale because the only way we can make one area of the zpf less energetic would be to cut off certain kinds of Em, so therefore there is less inbetween the two plates than on the outside so they are pushed together, you cannot get 1 atmosphere of pressure from a weak force. The mirrors are small but the force is universal so it pushes the same on everything, the pressure measured on the plates, when calculated [the plates are extremely small] is the equivalent of 1 atmosphere of pressure, so on all things the zpf exertes a pressure in all directions of around 1 atmosphere [i contacted a physcists about this] The casimir effect does not change the strength of the zpf, it makes it weaker in one spot, so currently everything in the universe is being pushed upon by 1 atmosphere of zpe vacuum pressure, the reason we cant feel it , is the same reason we dont feel the weight of air, we have enough pushing out and enough pushing in. So we are back where we started, why does such a weak force produce such a strong pressure, and who is right, the quantum physicists who say it is extremely powerfull or the classical physicists who say it isnt that powerfull?
Causal observer
Energy Content of Alcohols
After looking up on the net, it seems that beers generally have a energy content of 50kCal per Oz, which is roughly 1000kCal per pint. Which seems to me atleast to be an awful lot. I was wondering how they measured these things, is this the enthalpy of formation, or the enthalpy of combustion of the constituent products or something? If so does it inculde the energy of the ethanol, which being a hydrocarbon I assume has quite a lot of stored energy in it, and if so, si the human body capable of breaking down ethanol into CO2 and H20, which it would have to do to release these energies. Because I was (possibly wrongly) under the impression the human body couldnt break down hydrocarbons.
I know how they measure calories for other foods. They send a sample to a lab, the lab burns a set amount of the food and see how much it heats water up by. I'm assuming beers have a high energy content because the alcohol in the beer is burnable. As for the human body breaking down ethanol, ethanol metabolism says:
There is a common misconception that drinking alcohol leads to weight gain. This has never been proven in the literature and is the subject of ongoing debate among experts. There are many complex theories in the literature which hope to explain why drinking alcohol (i.e. high concentration alcohol such as vodka, as opposed to an alcoholic beverage like beer) may not lead to weight gain, but none of the answers are conclusive. It is known that some or even most of the alcohol that is ingested is not catabolized entirely to H2O and CO2. Instead, much of the alcohol that is processed by the body ends up as acetic acid in the urine.
It is clear that ethanol can be used as fuel for the body. As the article states, the major pathway for alcohol metabolism is ethanol -> acetaldehyde -> acetate -> acetyl (complexed with Coenzyme A) --> phosphorylation of ADP. This is not debated. What is debated is how much of each of these chemicals follow through in the reaction pathway before excretion. That some of the intermediates are excreted, and that a small fraction of the alcohol is metabolized by enzymes other than ADH-Σ (the type that usually deals with ethanol) serves to reduce the amount of energy one gains from ethanol. However increased ethanol in the diet tends to upregulate production of ADH (by smooth ER hypertrophy), which will increase the energy gained by creating more reaction opportunities before excretion. tucker/rekcut18:58, 12 February 2007 (UTC)[reply]
Sex ratio at birth
I doubt anybody knows the exact explanation, but why is that in the world more boys are born than women? In some countries, such as China, selective abortion in rural areas may explain this fact but a similar incident can be observed in European countries such as Italy or Spain, where I doubt that hypothesis has any basis. Any ideas? --Taraborn13:27, 11 February 2007 (UTC)
PS: Maybe this would fit better at the Humanities desk :P[reply]
There are three separate phenomena of interest related to newborn sex ratios (M:F):
The "baseline" or "natural" ratio of a healthy human newborn population appears to be about 105:100. The mechanisms are not known with certainty but are probably multiple. However, by late childhood, because of differential mortality, the ratio is close to even. By later in adult life, because of continued and accelerated male mortality, the ratio shifts markedly in favor of females.
It has been noticed that in certain conditions, such as war, the ratio shifts slightly in favor of males. This suggests there may be many subtle biological factors that differentially influence either fertilization success of Y spermatozoa or implantation success. Pheromones, coital frequency, anyone's guess.
A major cause of differential newborn sex ratios in some Asian countries, especially India and China, is simply selective abortion of female fetuses or infanticide of unregistered female births. This has resulted in imbalances as high as 120:100 in some populations of those countries (and obviously the governments are trying to discourage this). Attempts by parents to "choose sex" occur in western countries by a variety of mechanisms, but have a much smaller effect on the sex ratio because the methods are less effective than abortion or infanticide, because a smaller proportion of parents try to do it, and because not all prefer males. alteripse15:30, 11 February 2007 (UTC)[reply]
Blue: More women than men/Red: More men than women.Russia has more women than men (0.94 males per female, see Demographics of Russia); one of the theories put forward are that during the famines which occured in the Cold War, the low food levels were somehow detected by the body, and produced more female babies than male babies (in theory, a population of 1 male and 99 females can produce 99 babies in 9 months, but with very little genetic diversity, while a population of 99 males and 1 female could only produce 1 baby in nine months, but the genetic diversity of the population could be maintained far longer. As competition would be fierce for resources in a famine ridden country, in order for your genes to survive, you'd want to produce as many children and grandchildren as possible, hence the big female ratio is chosen). Now that Russia has more stable agriculture and access to food imports, the balance has shifted back to 1.06 males per female. Incidently, the population is one of the causes of mail-order brides. (See alsoSex ratio) Laïka16:55, 11 February 2007 (UTC)[reply]
A current hypothesis as to why females are ever so slightly selected against has to do with the differences in the X and Y chromosomes. Most simply, the X chromosome is larger than the Y chromosome, and more of a target for detrimental mutations (more base pairs = more of a chance that at least one BP will mutate). This is complicated greatly by the observations that women in fact have duplicate X chromosomes, that one is heterochromatized in the barr body, and by the existence of the Xist gene, but the difference, AFAIK, comes down to how much genetic material is present that, if destroyed, will decrease viability. tucker/rekcut16:49, 11 February 2007 (UTC)[reply]
A very simple hypothesis, widespread among laymen, is that the male sperm swim slightly faster because they carry a lighter load, and therefore win the race slightly more often... They only have to lug along a small Y chromosome instead of one of the much larger X chromosomes, and the smaller amount of DNA can be packed into a slightly smaller sperm head, which decreases viscous drag. --mglg(talk)02:08, 12 February 2007 (UTC)[reply]
Don't offer nonsense under the guise of "other people say". The chromosomes themselves make up such a small fraction of the weight of a spermatozoon that that "explanation" is like saying this locomotive will beat that one because the engineer weighs 190 lbs instead of 200 lbs. alteripse05:11, 12 February 2007 (UTC)[reply]
Please be WP:civil and do not characterize responses as "nonsense." One issue I did not see is the reported greater survival for low birth weight female infants, as related by a pediatrician and as seen at [5]. Why are male babies more fragile?Edison17:15, 12 February 2007 (UTC)[reply]
In fact, dear Alteripse, the human genome contains about 4 billion bases, at about 660 daltons each, which adds up to about 4 pg of pure DNA. A human sperm head is about 3x3x5 microns in size, and therefore weighs around 50 pg. Thus the pure DNA itself constitutes almost 10% of the weight of the sperm head! Furthermore, the extremely tight packing of the DNA in the sperm head is created with the help of packing proteins, mainly protamine, which contribute considerable weight to the chromatin (the packed protein/DNA complex). Thus the chromatin indeed constitutes a major part of the bulk of the sperm head, and the amount of DNA is a determining factor for the size, and thus the viscous drag, of the sperm head. There has been an extremely strong evolutionary pressure towards compact and fast sperm, due to sperm competition when a female is inseminated by more than one male (which is standard behavior in chimpanzees - no comment about humans...), and this has led to elimination of most non-essential cellular components in sperm. I share your concern that too many Reference Desk answers are offered "from the hip", but please save your most dripping levels of indignation for cases where your own footing is any more solid than that of the person you are complaining about... --mglg(talk)20:09, 12 February 2007 (UTC)[reply]
By the way, in the cattle industry there is a lot of money to be had if you can figure out a better way to sort bull sperm into male and female, and the difference in the amount of DNA is large enough that there is research going on trying to use phase microscopy methods to tell male and female bull sperm apart based on total dry-mass content. --mglg(talk)20:35, 12 February 2007 (UTC)[reply]
Do the math. The second sex chromosome is 1/46th of the chromatin, and the difference between the weights of 46XX and 46XY chromatin is at most about 1%. If the chromatin is 10% of the sperm wt, then you are looking at a 0.1% difference in weight of X sperm and Y sperm, which is a fairly tiny amount to explain a >5% differential success rate. The explanation is indeed nonsense. alteripse01:26, 13 February 2007 (UTC)[reply]
I hate to be picky, but sperm are haploid, and thus only carry 23 chromosomes... Furthermore, the 10% figure I gave above was just a lower bound to get the point across, it ignored all hydration water as well as the packing proteins etc.; in reality the chromatin is the dominant content of the sperm head. Therefore a better starting estimate of the volume difference would be 1/23, or about 4%. This is substantial difference, and it gets enhanced by the fact that the outcome of the race is determined not by the speed of a single sperm but by the speed of the fastest of a few hundred million independent sperm; for statistical reasons this has a much narrower distribution, so a small change in expected speed can have a large effect. Please understand that I am not arguing that this theory is necessarily true, I am only explaining its plausibility in the hope that you might reconsider whether your initial, eh, categorical dismissal was appropriate. --mglg(talk)02:49, 13 February 2007 (UTC)[reply]
"there is research going on trying to use phase microscopy methods to tell male and female bull sperm apart based on total dry-mass content." Wow! I never heard of female bulls before. Edison05:31, 13 February 2007 (UTC)[reply]
Molecules orbiting the sun
Is there anything known about the dynamics of singele molecules orbiting the sun? Mechanically there should be no difference to larger bodies, but radiation pressure from the sun should have a major and probably, due to different emission lines, a selectiv effect.
(after eit conflict) The sun's solar wind would push any orbiting gas or dust out to the heliopause, well beyond the outermost planets, in short timescales in astromical terms. The solar wind is powerful enough to significantly erode the atmospheres of the inner planets, apart from the Earth, which is protected by its magnetic field. Gandalf6117:58, 11 February 2007 (UTC)[reply]
Yellowing of plastics commonly results from exposure to the invisible form of radiation labeled, Ultra-Violet light. This yellowing phenomenon is technically called photo degradation and is common to many objects subjected to Ultra-Violet raditaion. An example of that is the yellowing of a newspapers left in sunlight. Some plastics are more resistant, such as the Acrylics. On the other hand, a stabilizer, actually a photo-absorber, can be added to the chemistry. After a while, even plastics, rubbers, etc., with these photo-absorbers will degrade, too. Photo-absorbers are like a balloon. Whereas a balloon can only hold so much air before it "degrades" by exploding, these photo-absorbers also become exhausted over time. Micro-wave ovens, as you likely know, are a form of radiation. Ken 64.231.90.17617:18, 11 February 2007 (UTC)[reply]
Ken, are you saying that the microwave's own radiation can cause the plastic on its outside to yellow? Or would the yellowing be primarily from sunlight? --Lph19:44, 11 February 2007 (UTC)[reply]
I was certain that microwave ovens were a form of matter. I guess you learn something new every day. :) One important difference between microwaves and UV is the frequency: the short frequencies in radiation of higher energy than the visible are often able to break chemical bonds directly (ionizing radiation). Microwaves generally only have enough energy to make molecules ring like tuning forks or to set them spinning. --Joel08:30, 12 February 2007 (UTC)[reply]
I've always gotten the impression that the yellowing (or in some cases pinkening) or the plastic in the microwave was due to interactions with colouring in the hot food. I've had brand new plastic bowls go pink after just a couple of times when I've used them to re-heat spaghetti sauce - yet stay clear for months when used to cook peas and beans. No amount of cleaning will get them clear again - so I suspect a chemical change - but I'm not convinced that microwaves were the cause. SteveBaker20:49, 12 February 2007 (UTC)[reply]
Oh wow, I just realized the original question could have been referring to plastic dishes inside the microwave; I thought it was about the outer plastic housing of the microwave itself. --Lph15:39, 13 February 2007 (UTC)[reply]
South-To-North Water Diversion (China)
I can't find anything on Wikipedia on the South-to-North water diversion in China. I found one article here but I want more articles. Normally I turn to Wikipedia's links section, but as I said, I can't find the article. It seems like too big a thing for you all to miss. Thanks. --70.56.231.172 16:28, 11 February 2007 (UTC)
Me again. I'll post this to requested articles as well.--70.56.231.17216:33, 11 February 2007 (UTC)[reply]
Vitamin - Sterilization
Hi, What is the most suitable method to sterilize a Vitamin , which is needed to supplement a bacterial medium ? Thanking you, --Pupunwiki17:38, 11 February 2007 (UTC)[reply]
I was reading about Einstien's famous equation and was stuck by something.
His equation states that E=mc²
However, if you solve for m you get the equation
However, the equation shows that matter is actually energy divided (?) by the speed of light squared. Is this right? and if it is doesn't that mean that you could "in theory" create something that can have all of it's matter instantly converted into pure energy by destroying it (like fire)? Also, can the principle of nuclear fission and nuclear fusion (smashing one or two radioactive particles together to release energy) be applied to ordinary objects? i.e. firing a neutron or protron at ANY type of atom and getting energy out of it
Even cooler is that when you car is rolling and has regular kinetic energy, it's effective increase in mass is . Simply by moving your car, you get that additional mass. --Tbeatty21:28, 11 February 2007 (UTC)[reply]
Obviously no new atoms or particles are created. The work expended on tensioning the spring is stored as elastic energy in the spring, or more explicitly in the form of electromagnetic field energy between the atoms. To get the flavor of what is going on, think as a simpler example of pulling on the two atoms in an O2 oxygen molecule. The pulling force will very slightly increase the distance between the two oxygen atoms, and increase the total amount of energy in the electric field between the two nuclei and their orbiting electrons. Something similar happens in the spring. The added energy in the electromagnetic field does indeed have a mass (which interacts with the gravitational field just like any mass), and would make the mousetrap read very slightly heavier if placed on a hypothetical very sensitive scale. How much heavier? Well, let's do the math! Let's say tensioning the spring on a small mouse trap requires pushing it by an average force of 10N for a distance of 10 cm. That would store one J of energy, which corresponds to a mass of m = E/c^2 = (1 J)/(3*10^8 m/s)^2 ~ 10^-17 kg = 10^-14 g. Multiplying this by Avogadro's number 6.023*10^23 yields ~6 billion atomic mass units. Since the atomic weight of iron is 56, that is as much mass as 6 billion/56 ~ 100 million iron atoms. More than you'd think, huh? --mglg(talk)01:56, 12 February 2007 (UTC)[reply]
The equation simply shows that mass and energy are interchangeable. The c-squared part comes about because when you convert a very small amount of mass into energy - you get a heck of a lot of energy because c is an ungodly large number and c-squared is insanely big. This explains why atom bombs (which actually convert a tiny fraction of their mass into energy) are so amazingly powerful. Conversely - as others have said...it doesn't matter whether your cup of tea is hot or cold - it doesn't seem to get any heavier. In truth, the relatively small amount of energy in hot tea compared to cold tea results in an utterly negligable amount of extra mass. The speed of light is about 300,000,000 meters per second and squaring that gets you 90,000,000,000,000,000 m2/s2. The amount of heat energy in a cup full of boiling water compared to a cup full at room temperature is about 250 Joules. But that means that the increase in mass of your teacup when it's heated up is 250/90000000000000000 kilograms. (0.0000000000000028kg) - but since (for example) an oxygen atom weighs something like 0.022/Avagadro's number kilograms - and Avagadro's number is another ungoldy huge number (6x1023) or 0.000000000000000000000000036 kg, your tea got heavier by about the mass of 75 billion oxygen atoms.
It surprises me too. I think we underestimate how much less an atom weighs. If you ask somebody to guess (not calculate) how much would 75 billion oxygen weigh, I suppose their answer would be in grams or fractions of a gram -- WikiCheng | Talk07:32, 12 February 2007 (UTC)[reply]
Er. I know very little about relativity theory, but the above calculation seems to be a misunderstanding or misapplication of Einstein's equation. If my understanding is correct, you can only apply this famous equation to situations in which special relativity applies (significant fractions of light speed). In classical situations where you are considering invariant mass, I don't think you can apply E=mc^2. E=mc²#Background seems to support this. Remember that E=mc^2 is only a special case; it's part of a more general equation:
Anyway, someone who actually knows something about relativity should be able to clear this up. -- mattb@ 2007-02-12T07:29Z
Actually, it's the other way around. The Equation E = m.c2cannot be used at high velocities. Here's why:
Relativity theory defines the total energy of a particle as:
Which is perhaps analagous to the definition of mechanial energery in classical mechanics (potential + kinetic energy). Relativity also defines Erest (the rest energy) and Ekinetic (the relativistic kinetic energy) as follows:
For resting masses Ekinetic = 0 and Etotal becomes mc2. However at significant velocities, the relativistic kinetic energy cannot be ignored and the formula loses its "conventional" form. —LestatdeLioncourt14:19, 12 February 2007 (UTC)[reply]
Questions like this and the answers are fascinating, but to clarify, please state where the extra energy is stored. It is confusing when you state the energy as "equivalent to x number of atoms of oxygen or iron created." Is the energy in fact stored, in the mousetrap example, in the preexisting atoms of the spring, without any new atoms created, so each of so that each metal atom in the spring (which might weigh a few grams in total) increases its mass by some fraction? Could someone make a reasonable assumptiion of how many iron atoms (or other alloyed elements)store the energy and by what percent the mass of each increases? Ditto for the boiling water, where the number of water molecules is easier to determine. Thanks. Edison17:07, 12 February 2007 (UTC)[reply]
Please first reread my answer above. No new atoms are created. In the case of the mouse trap spring, the energy is stored in the form of electromagnetic field in between the atoms (really between the nuclei and the electrons). This field has gravitational mass, because it contains energy. In the case of the hot water, the energy is stored in the form of kinetic energy of the water molecules – they move around faster. Because of their increased velocity, their relativistic mass increases, and therefore their gravitational mass. The invariant mass, or rest mass, of each molecule stays the same, however. --mglg18:29, 12 February 2007 (UTC)[reply]
Rock apes?
I'm currently reading Philip Caputo's A Rumor of War, a story about the author's experiences in 1960s Vietnam. He occasionally makes reference to an animal called a "rock ape." My question is, what exactly is a "rock ape"? Is it like a gibbon, or a macaque, or what? The rock ape wikipedia article redirects to a webcomic and offers no help. 68.252.189.13323:45, 11 February 2007 (UTC)[reply]
A google image search of "rock ape" gives me a Barbary macaque (not an ape, but eh? a doubt a lot of GIs/Vietnamese knew the difference in the 60s) not sure about the etymology. --Cody.Pope 00:04, 12 February 2007 (UTC) Ah, yes now I see their range is all wrong. I'd still bet on a macaque over a gibbon, since they rarely leave the trees to hang-out in and around rocks. Also, given that Europeans already called one kind of macaque an ape, I'd bet a trend at large is in play. --Cody.Pope00:36, 12 February 2007 (UTC)[reply]
Nah, I was simply saying that superficially all macaques look pretty much the same (compare this guy to this guy) also from the text of the book it is pretty clear they're talking about a mischievous living animal (also calling it a monkey once or twice). To me that's a macaque. Also, check out this list of monkeys/apes that live in Vietnam. --Cody.Pope01:46, 12 February 2007 (UTC)[reply]
Hello.
I asked my Doctor where you can donate your body to Science when one passes over to the other side, and the Doctor told my wife and I that it was done through the University of Oueensland.
Can you please send me your documents that you need to do this proceedure.
Here is my address which is a temporary address before we move into our new home in Burpengarry in five months time.
<removed address>
Regards
Richard and Moyra Papworth
(edit conflict)This is Wikipedia, the online encyclopedia that anyone can edit, not the University of Queensland. It is likely that you found our article on the university and belived we were the school itself. I can assure you that this is not so, and that the aforementioned university will most likely need to be contacted for this matter. Also, Wikipedia cannot offer legal/medical advice, and this question involves both. - AMP'd02:25, 12 February 2007 (UTC)[reply]
To whom it may concern-
Why does the area around our eyes getting darker when we don't sleep? I have heard theories, the best one is that it is venous congestion from prolong eye opening.
Thanks
— Preceding unsigned comment added by Salim19 (talk • contribs) 02:39, 12 February 2007 (UTC)[reply]
Can someone please explain phase angle and why capacitors and inductors and such change from it in layman's terms? I know the math but don't understand it or the concept really.69.29.62.7302:43, 12 February 2007 (UTC)[reply]
I mean, what is actually going on in RC, RL, RLC circuits
In an AC circuit without L or C components, the voltage and current are "in phase" or, at all times proportional. The introduction of L or C components in a circuit will cause the voltage and current at various places in the circuit to be other than exactly proportional. The "phase angle" is a measure of the disproportionally with respect to time where 360º = 1/f. hydnjotalk03:43, 12 February 2007 (UTC)[reply]
In fewer words, phase angle (in circuit phasor notation) is merely a representation of time delay. A phase angle of zero with respect to some point represents no time shift, while a phase angle of 360 degrees (2 pi radians) represents a time shift of one whole period of the phasor frequency. -- mattb@ 2007-02-12T03:52Z
so, because inductors and caps store energy, the wave at any given time "come out" of them at a time delay?
Yes. Because these lump elements store energy, they introduce a delay. -- mattb@ 2007-02-12T03:52Z
thank you. I figured that was what was going on but I wasn't for sure
I always thought of a capacitor as a device which hates to see the voltage change. If the voltage starts to change, the cap will absorb current (charge) or pay out same to try and keep the voltage constant. The voltage change lags behind the current change in a capacitor. On an oscilloscope, with AC going through a capacitor, the peak of the current waveform leads the peak of the voltage waveform by 90 degrees. An inductor hates to see the current change, and produces a counter EMF to oppose the current change, so the current change lags behind the voltage change. On a scope, the peak of the voltage waveform leads the peak of the current waveform by 90 degrees for an inductor. In either case, the presence of resistance decreases the lead from 90 degrees. Edison16:57, 12 February 2007 (UTC)[reply]
Total oxygen-producing capacity of the Earth's vegetation
Have there been scientific studies to estimate the total oxygen-producing capacity of the Earth's vegetation? If so, what do we know about it? If the current trends of population growth and deforestation continue, at what point will we be in danger of not having enough oxygen? --71.175.23.22604:11, 12 February 2007 (UTC)[reply]
It's likely that the Earth would become unlivable due to excess carbon dioxide long before the oxygen started to run out. The fact that minerals like coal and diamond are buried are the reason that oxygen is so available on the Earth's surface; it was all CO2 to begin with. The other question to ask is: what do we use oxygen for? Well, we use it to oxidize fuel, and we breathe it to oxidize food. Food and biofuels like wood or whale oil get their carbon and hydrogen from CO2 and water that were (in geological terms, anyway) recently split by photosynthesis. If we can produce enough food for our population, we will, by default, have produced enough oxygen to metabolize that food. Fossil fuels, as I mentioned earlier, were separated from their oxygen much longer ago.
We will never mine all of them, though: most just aren't accessible. If accessibility weren't a problem, we would be stopped from digging up coal (and from living) by a greenhouse effect like the Earth hasn't seen in a very long time: we're worried about the effects we've seen while going from 280 to 380 parts per million of atmospheric CO2, but using up half the world's oxygen would bring the concentration up to 10.5%, or 105,000 ppm.
I hear that the developers of the first nuclear bomb worried that it might ignite the atmosphere, forming nitrogen oxides and using all the world's O2 in one fell swoop, but that obviously didn't happen (we now know that it's impossible). I haven't heard any other serious scenarios where we might use up all the oxygen without the side effects of such a process killing us all first.--Joel09:12, 12 February 2007 (UTC)[reply]
The "igniting the atmosphere" scenario was actually about igniting a nuclear reaction such as fusion of two nitrogen atoms to form aluminum. Such a reaction would be exothermic and therefore potentially self-sustaining, and it was thought that the blast might be hot enough to start it. Calculations using a more detailed model showed that it would not. --Anonymous, February 13, 2007, 04:14 (UTC)>
CO2 is pretty poisonous actually - If there is 5% of CO2 in the air, humans will die - irrespective of how much oxygen there is. (Prolonged exposure to air with more than half a percent of CO2 is considered hazardous...again, irrespective of the amount of oxygen). So the key thing about plants is not so much that they are producing oxygen as that they are removing CO2. Incidentally, plants only consume CO2 when they are exposed to sunlight - in the dark, they consume oxygen and actually produce CO2 - just like animals do. As for how much they produce - I have no clue...but green phytoplankton in the oceans are another major way that CO2 gets absorbed out of the atmosphere so it's not just "plants" in the usual sense of the word. SteveBaker20:38, 12 February 2007 (UTC)[reply]
Autorotation is indeed the answer - but it's something that takes skill to learn - and it's very nerve-wracking. When the engine dies, you have to tilt the blades of the rotor so that as the helicopter plummets down ("like a stone"), the blades turn like a windmill in the airflow. This does two things. Firstly, the rotor acts like a parachute - slowing down the rate of fall of the helicopter - secondly, the blades start to spin faster and faster (because it's acting like a windmill). At some appropriate height - just before you hit the ground - the pilot has to reverse the pitch of the blades again so they are back the way they'd be if the engine was still running. That causes them to start pushing air downwards - just like they'd do if the engine was still running - but because it's not, the rotors lose energy and slow down dramatically. But (ideally) that last downward push is just enough to let the helicopter gently settle the last few tens of feet onto the ground. The nasty part for the pilot is judging his height just right for that final manouver. If he does it too soon then you're still way above the ground with the rotors not spinning anymore and the helicopter surely will plummet like a rock. If he leaves it too late then that last burst of energy that would have slowed you down doesn't happen in time and you'll still hit the ground too fast. This is a tough skill to learn and it's very, very nerve wracking to do 'for real' because if you get it wrong - you're probably dead. So most helicopter pilots only do it once or twice in a real helicopter - and hope to heck that they never have to do it in a real emergency. The best way to learn is in a flight simulator where you can practice as many times as you need to learn the skill well. SteveBaker20:28, 12 February 2007 (UTC)[reply]
An old Navy pilot told me that any landing you walk away from is a "good" landing. I would think that, by analogy, any landing that leaves the aircraft even repairable would be a "near perfect" landing. All this from the perspective that it is an amazing feat to get anything heavier than air to fly at all. Edison05:39, 13 February 2007 (UTC)[reply]
arun's ques.
does human urine contain sperm?
Only if the human in question has ejaculated recently so that their urinary tract has left-over sperm paddling around.
Is it possible to keep something - such as a mattress, cold or chilled without electrical power? Is there a cooling gel or system that could keep something cold for hours?
THANK YOU!!!
A water bed can act as an enormous heat sink, such that if you don't heat it, it can actually be dangerously cold (e.g., to an infant or bedridden person). In general, anything that can absorb and radiate heat away from your boday faster than you can produce it, will stay "cold" indefinitely. --TotoBaggins14:39, 12 February 2007 (UTC)[reply]
Without consuming power, it can only stay as cold as the environment it's sitting in - this is dictated by the second law of thermodynamics - so we're pretty sure there is no 'get out clause' that would allow you to build something that can cool itself without power. Even a large water mattress will eventually settle down to somewhere around room temperature. However, that will feel cool to your skin because we are much warmer than room temperature and heat flows from warm things into cooler things. But - our perception of coolness is not strictly one of temperature. If you take a chunk of metal and a chunk of plastic that are at exactly room temperature - and place your hand on the metal, it will feel cooler than the plastic. That's because our perception of temperature is the amount of energy our skin loses or gains from whatever it's touching. Since metal conducts heat away quite efficiently while plastic doesn't, we feel more heat from our skin flowing into the metal than into the plastic - so plastic feels warm to the touch and metal feels cold - even when they are at the same temperature. So if you take a nice cuddly blanket (which is a great insulator...like the plastic) that's been sitting in the same room as a waterbed (which conducts heat away like a chunk of metal) - then the water bed will FEEL as if it's colder than the blanket - even though it's not. So your FEELING of cold can indeed be kept up without electrical power - although the temperature cannot. Providing the water bed can lose heat into the room faster than your body can feed heat into it (which it easily can) - then you'll feel cool all night. BUT if the air temperature ever gets above body heat (which can happen here in sunny Texas) - then the opposite would happen. Because the room temperature is above your body temp - and the water bed will eventually come to be the same temperature as the air, a water bed will conduct heat INTO your body much more efficiently than a blanket would - so you'd feel a lot hotter in the water bed. But the second law of thermodynamics is what prevents you from making a refrigerator that doesn't use any electricity. The laws of thermodynamics are such kill-joys! SteveBaker20:13, 12 February 2007 (UTC)[reply]
Without consuming some form of energy you will not be able to keep something cold. But this doesn't mean that it must be electrical power. If you take a metal plate for example and let alcohol drop on it at a steady rate, you will keep this metal plate cold for a while. Similar experiment with different materials (ether, amonia) are also possible. Just keep in mind that some form of liquid must evaporate to become a gas (i.e. absorb energy). The second law of thermodynamics doesn't prevents you from making a refrigerator that doesn't use any electricity. Indeed due to the second law of thermodynamics you can make a refrigerator that doesn't use electricity. For more information look at Einstein refrigeratorMr.K.(talk)13:19, 13 February 2007 (UTC)[reply]
Astronauts Pills
I heard a while back that there was a pill given to Astronauts to relieve sexual tension or urges once in space. Is there any information on this or was this just a rumor?
In any case, one suspects they have more important matters on their minds. There is no better anaphrodisiac than having to pay close attention to your survival. They are considered members of the elite 100km high club without going that bit further.--Shantavira09:15, 13 February 2007 (UTC)[reply]
I read somewhere that there was a pill in which the Astronauts would have "sex" on their dreams while they are sleeping. And then the drug dealers got a hold of this drugs and where selling them. Has anyone heard of this story?
Oribit
Is it a valid comment to say that “an aeroplane orbits the Earth, if the aeroplane circumnavigates the Earth?" i.e. one complete flight around the earth = one orbit.
I am of the opinion that this is not an orbit (in a scientific sense), but I just want to get the general consensus. Thanks RaGe16:23, 12 February 2007 (UTC)[reply]
Once you start altering the meaning of a word, it could mean anything you want:) Is a person standing on the ground "orbitting", given that he is circling the earth's rotational axis once a day? DMacks18:35, 12 February 2007 (UTC)[reply]
"Orbit" is correct according to the dictionary, (an approximately circular or elliptical path traced by something in motion OED) but it's never used in that specific sense in practice. "Circumnavigation" is the right word in that situation. --Shantavira18:33, 12 February 2007 (UTC)[reply]
If this is just a question of dictionary definitions - then indeed, standing perfectly still for 24 hours would imply you were orbiting the earth. But this is the Science Desk - not the English Lit. Desk and scientists very often have different meanings for words than the general public...so we need to talk about the true distinction between what a circumnavigating aircraft does compared to something like a satellite that is 'in orbit'. When we talk about something being "in orbit" around the earth, we generally mean "in a stable orbit". That means that without firing any rockets, you'll keep going round and round the earth pretty much forever.
That's clearly not what our airplane is doing. As soon as it shuts off it's engines...kersplat...no more "orbit" - it's in a highly unstable orbit. To be in a stable orbit, you need to be going around the earth at a speed such that "centrifugal force" (a term most physicists hate - but which none the less serves our purpose) exactly equals the force of gravity. That's a rather precise speed that depends on your altitude above the earth. SteveBaker19:59, 12 February 2007 (UTC)[reply]
Steve goes wrong at the end: what he's describing are the conditions for a stable circular orbit. An elliptical orbit accommodates a wider range of speeds, and the speed of the object will vary continuously -- fastest when lowest, slowest when highest -- but this is still stable, so long as the lowest point is for practical purposes above the atmosphere. For an orbit that isn't circular, the speed at the lowest point will be faster than for a circular orbit at the same height (so you still need a minimum speed to be in orbit), and the speed at the highest point will be slower than for a circular orbit at that height. --Anonymous, February 13, 2007, 04:24 (UTC).
The speed of light is always the same-however fast you are moving, light always passes you at 3x10^8ms^-1. So if you were on a photon travelling at 3x10^8, and another photon passed you it would be travelling at 3x10^8 relative to your speed. However from the other photon, you would pass it at 3x10^8. This seems to mean two photons can pass each other, both going at twice each others speed. How the **** does this work?Hidden secret 717:27, 12 February 2007 (UTC)[reply]
From one photon the other would appear to be moving at 6x10^8, so could this be extrapolated out further to suggest that a photon could travel at infinite speed relative to one travelling at infinity-3x10^8, which was relative to one travelling at infinity-6x10^8&c:)HS7
It is misleading to phrase the question in terms of photons, because, in a sense, photons don't "experience" time at all. No photon could "pass" another photon. So let's instead consider an astronaut moving at 0.9c relative to the Earth. A photon passes her, and she observes its speed to be c relative to her. Would an observer on Earth then have measured the speed of the same photon to be 1.9 c? No, the Earth observer would also measure a speed of c. It will appear to the Earth that the relative speed of the photon to the astronaut is 0.1 c, but that the astronaut measures a relative speed of c because of the strange things that relativity does to the astronaut's measuring devices: the astronaut's clocks appear (to the Earth observer) to go too slowly, and her rulers appear (to the Earth observer) to have shrunk.
If we instead consider a second astronaut that passes the first one, at a relative speed of 0.9 c, and a third astronaut that passes the second one with a relative speed of 0.9 c, and a fourth astronaut that passes the third one etc., then all of these astronauts will move at less then c relative to the Earth observer. Even if there is an infinite series of such passing astronauts, their speed relative to Earth will only approach c, never exceed it. --mglg(talk)18:52, 12 February 2007 (UTC)[reply]
Photons don't have a rest frame of reference. That means that there is no relative velocity to even speak of. Imagining yourself as the photon and being "at rest" with respect to other photn, while a thought experiment, is simply not a physical reality. Tbeatty20:26, 12 February 2007 (UTC)[reply]
Yeah, you can't have a photon pass another photon. Think about what you mean by "passing" here — you mean that one photon, going c, is surpassed by a photon on a parallel path going at a speed greater than c. You're basically saying, "the speed of light is constant (in a vacuum), but what if light could go faster than the speed of light?" Which is a nonsensical question and one which doesn't really appreciate what the "speed of light" means. You might as well say "if the top speed of a certain model of car is 50 mph, and another of the exact same model of car goes by it at 100 mph"... see the logical problem? --24.147.86.18723:13, 12 February 2007 (UTC)[reply]
Alleles identical by descent
No disease model is given, nor is the information about the genotypes of parents and a child
in a family. Is it possible to tell the IBD score from father to son?
In another case, we have a family in which father and the second child are affected,
mother and 1st child are not affected. what would be the IBD score?
That's pretty much just the color that Rifampin is (reddish) +/- some additional yellow from urine (--> reddish-orange). You're excreting the drug in your urine (mostly) and also in every other bodily fluid, which is why you were warned (or should have been) to avoid using soft-contact lenses if you wanted them to stay clear instead of red. - Nunh-huh21:38, 12 February 2007 (UTC)[reply]
Is table salt the same as the salt in tears?
Okay, so my friend says the salt in your tears is the same as table salt. My other friend (who is nerdy) says the two are completely different because table salt contains iodine, but this isn't the only difference. I need you guys to settle this once and for all. NIRVANA276420:59, 12 February 2007 (UTC)[reply]
The main salty component is the same in both (sodium chloride). But as your nerdy friend pointed out, table salt also contains small amounts of some other compounds like iodine, and anti-caking aids. Tears, of course, also contain many other things: many other salts, a large number of different proteins, etc. But, again, their salty taste comes mainly from the same chemical compound as is in table salt. --mglg(talk)21:09, 12 February 2007 (UTC)[reply]
By the way, there is just one salty tasting known substance. It is sodium chloride. If something tastes salty, there is sodium chloride inside. Mr.K.(talk)13:29, 13 February 2007 (UTC)[reply]
Really not true. Chemically "salt" is a generic name for a large class of ionic compounds. Not surprisingly, several of the common mineral salts also taste "salty", which is how the group originally got its name. Calcium chloride and potassium chloride are ones you might encounter as a sodium chloride substitue in food. A large numbers of "salts" will also taste bitter, and some organic salts even taste sweet. Dragons flight17:12, 13 February 2007 (UTC)[reply]
MSG tastes savory and not salty. Potassium chloride tastes bitter, although it is a salt substitute for sodium chloride for preserving food. Calcium chloride is a equally a substitute for Sodium chloride for preserving food. See this article and this for more information about the taste of calcium chloride. In the first article the authors try to overcome the taste of calcium chloride through "an oily solution of calcium chloride, which reduces the bitter taste of the salt." The second also points to the bitter taste of calcium chloride: "Calcium chloride is not the ideal calcium salt to use in food fortification because of its high bitterness ratings". The only source about salty taste of calcium chloride that I found was wikipedia itself. MThis is due mainly to the anatomy of our taste_buds for saltiness, which work through ion channels. Specially Na+ is able to pass through this channels.Mr.K.(talk)19:42, 13 February 2007 (UTC)[reply]
A drug categorization dispute
Would anyone be willing to participate in settling a dispute? Please read Wikipedia talk:WikiProject Psychedelics, Dissociatives and Deliriants#Categorization dispute. I know this is hardly the place to ask a question like this, but I've been trying to enlist help from users in Wikipedia:WikiProject Psychedelics, Dissociatives and Deliriants] to help, and not a single Wikipedian has made any comments, and we're a far cry from reaching a consensus on a debate we're having. The debate is over the definition of "psychedelic," as Wikipedia currently uses the word to describe a very specific class of serotonergic and cannibinoid drugs. I argue that the definition is too stringent. The defender of that definition and I have cited many sources to defend our respective views, and they're well referenced, so simply reading through and leaving your two cents would help us reach a consensus. Thanks! Jolb21:20, 12 February 2007 (UTC)[reply]
I looked at the page Hallucinogens and the other links and saw the way they have been broken up into three classes, I also looked at the points you both made. I have no dissagreement with either..
Hello, I'm the anonymous user who posted "Science and the supernatural" on Feb 9th. I have another, related question. Creationists and Intelligent Design proponents sometimes argue that "Just as a the existence of a watch implies that there must be a watchmaker, and it would be perverse to suggest that the watch came about by random chance, so a complex universe [or "irreducibly complex" structures in that universe] shows that there must be a God." Thus, science would prove the existence of God. I have read people like Isaac Asimov try to refute this argument, insofar as it is offered as a scientific proof, pointing out that the whole point of science is to find blindly operating natural causes and that "to surrender to ignorance and call it God is premature and it has always been premature." Yet, when we find a watch (or even some kind of machine we do not recognize), we do assume that there is an intelligent designer. The existence of humans is an accepted scientific fact (I think), as is the fact that watches are intelligently designed. So where is the flaw in the analogy? Are humans supernatural beings? Or is the analogy valid? Cause I'm not entirely sure that ID is a bad idea. EDIT-made my Question more clear 69.223.156.24122:37, 12 February 2007 (UTC)[reply]
I see no real flaw in your arguments - it's just that very little is 100% certain - that's the only problem.
Also it is possible that humans are supernatural beings - I've often wondered this - but it's neither provable or disprovable as far as I can tell.
There is no real explanation for existance - as you have noticed I think - but if we say that it must have been made by something eg god (as per the watch) the problem continues ie who made the god.. I can tell you I found the whole question fundamentally unanswerable, though I admit I still think about it.
Lots of people are fairly certain that god either exists or doesn't exist, who however can be certain? - everyone thinks about it don't they?87.102.16.19722:53, 12 February 2007 (UTC)[reply]
By the way I'd like to point out that it's not actually scientific method you are describing but more logic and reason that you are using to prove/disprove the existance of things. Better than science in my opinion. You might want to start reading philosophy articles - though there's a lot to wade through you've got till eternity to do it! Good luck - remember that the 'greatest minds' of world history haven't really cracked this one.87.102.16.19723:04, 12 February 2007 (UTC)[reply]
The reason the watchmaker analogy is used by creationists is that it's emotionally appealing rather than because it's intellectually sound. It's appealing because in our experience, all watches are made by humans. Therefore if we find one, we assume it was made by a human. But this is not because the watch is "complex", it's because all the watches we know were made by people. One might with equal (or equally little) justification say that the presence of a rock implies a rockmaker. And there is no analogous experience that all humans are made by gods. The statement presumes the same thing that it seeks to prove, so it's not intellectually sound; its purpose is to persuade, not enlighten. It also fundamentally misrepresents evolutionary theory, as no evolutionary theory claims that any complex structure ever arose "by chance". - Nunh-huh23:07, 12 February 2007 (UTC)[reply]
Irreducible complexity is a different concept than just complexity — I just want to point that out. Paley's original watchmaker argument was not about irreducible complexity (irreducible complexity only becomes required later when you have an alternative method — gradualistic evolution — to argue against). Irreducible complexity is an entirely different thing and should be regarded quite separately from your question (IC says that some structures could never have naturalistic/evolutionary explanations because removing one element of them would be useless, ergo any sort of evolutionary process would never have been able to create it. This is quite different from the argument that complexity implies a designer, in general).
As for the problem — it depends entirely on whether you consider the explanations of naturalistic "design" (design without a designer) to be valid. The main argument against it is that there are some principles which we generally call naturalistic which seem to, without any additional intelligence, give rise to incredible complexity. But whether or not you consider those principles to be evidence of further interaction by a God or not — i.e., maybe he set forth the principles in question — or whether you consider them to be "truly" naturalistic will depend primarily on your prior philosophical/religious convictions, because there is no compelling logical reason to choose one explanation or another. The "scientist" would perhaps say that the introduction of superfluous concepts seems unnecessary and illogical but that is an aesthetic, not a logical, preference. --24.147.86.18723:08, 12 February 2007 (UTC)[reply]
Which is actually an argument that works easier in Paley's favor than against it. For Paley it is clear that if you agree that there is a watchmaker God then you will find plausible that existence itself is at the discretion of such a God. Which is not necessarily any larger of a logical jump than saying that things "just exist" for the sake of it, which is pretty much the closest answer you would get from modern science (officially science would actually just refuse to give an answer, as it is not really a question within its purview, but to me that doesn't really help much). --140.247.242.7518:07, 13 February 2007 (UTC)[reply]
The is the dumbest argument in the world! Let me explain why.
"A watch implies a watchmaker, therefore a human implies a God".
The biggest problem is this "How do you recognized a watch (a thing that is designed) when you see one?" Because of your experience of a watchmaker(designer) or stories of a watchmaker(designer). Now ask yourself this question, if you had never had the experience of God or stories of God, will you conclude that finding a human implies the existence of God. Of course not.
What you are saying is:
Things that are designed are "complex looking" therefore things that are "complex looking" are designed. QED.
It isn't the "dumbest argument in the world", and generally when one encounters an argument which has been discussed up and down by dozens of philosophers for hundreds of years assuming that it is simply "dumb" is more a statement about yourself than it is one about the argument. Paley's actual argument, which you likely have not read, is much more specific about what he considers this complexity to be, and he appeals to the very general experience one has with things like mechanical clockwork, which you'd be a fool to think doesn't imply a designer (Paley's argument is in many ways a very pragmatic one, appealing to what "any reasonable person would believe" rather than attempting to define everything from first principles). The only reason Paley's argument doesn't really work is that we do, now, have explanations of how highly complex things can come about without intelligent intervention. Paley's argument simply says that authorship and complexity seem connected in the human technical world, and there is no a priori reason not to think they would be connected in a biological world. It's someone like Darwin who gives you a possible a priori reason for doubting that. --140.247.242.7518:07, 13 February 2007 (UTC)[reply]
To the original poster: I can specifically recommend Richard Dawkins's book, The Blind Watchmaker, which as its title implies addresses Paley's Watchmaker fallacy directly.
Why is the analogy fallacious? My own answer is that you can come at it from two directions. One is that, although life is undeniably complex, hypothesizing the existence of a watchmaker -- a god -- implies much more and even more unimaginable complexity. Life may be improbable, but an omnipotent god is even more so!
The other answer, the other direction to come at it from, is that evolution and natural selection actually work much, much better and with much more finesse than you might at first imagine. It's very hard to believe at first; it seems nearly impossible that (to cite everyone's favorite example) something as magnificent as the eye just happened to evolve, by random accident. Again, read Dawkins for a better understanding of this -- he explains it very eloquently and convincingly.
If I were an omnipotent god and I wanted to create life, there's no way I'd have the patience to muck around with individual eyeballs and irises and ribs and stuff; instead I'd invent evolution and natural selection, and let life design itself for me. —Steve Summit (talk) 02:35, 13 February 2007 (UTC)[reply]
That's a good point. You know, this sort of topic came up in my biology class. In this post, however, I will give my personal opinion on the matter.
If there is a God, which I firmly believe as a Roman Catholic, that wanted to create a diverse and free race, then he would have created a system to do so. Let's take into the perspective of Nazism. The Nazis attempted to acheive a Master race by means of experimentation with women in the concentration camps. In this case, Hitler tried to play god by means of manipulating the human population (selective breeding? eugenics?). As we know now, trying to create your own race by means of using your own power might not be the best thing for the human population right now. It would strip us of our individuality and uniqueness. Now in the case of human society today, generations of children are produced by natural process such as fertilization.
In conclusion, I believe that God created the human race along with a means of naturally producing further generations of humans to create a completely diverse population, with creatures of different backgrounds, unique characteristics, and individuality.--Ed¿Cómo estás?03:19, 13 February 2007 (UTC)[reply]
There are so many ways around this watchmaker analogy. For example: Suppose you have the components to make a watch - a bunch of gearwheels and springs and stuff. You shake them up and dump them at random onto the floor...what are the odds that there will be a complete, functioning watch just sitting there on the floor? Almost zero...really, astronomically small. But evolution has been operating for three billion years - hundreds of thousands of teeny-tiny viruses and bacteria have been breeding in every drop of water in our 1,340 million cubic kilometers of ocean - reproducing every few minutes for all of those billions of years. If every single one of those events were you tossing the watch parts onto the ground - does it seem so improbable that one of those would turn into a functioning watch just by chance?
But things are much, much better than that in the world of living creatures. They have DNA - this allows the sucesses of one generation to be passed onto the next generation. Watches don't have that. It they did then if by chance two gear wheels happened to assemble themselves together, then they will be ready-assembled for the next watch-tossing event. This speeds things up no end.
A better example is Richard Dawkins one of asking what the probability of a million dice being rolled and all coming up sixes. The odds are far, far too long. If you rolled dice from the big bang until the end of the universe - the odds are slim that you'd ever see a million sixes. However, if you roll the dice once and are allowed to keep the sixes you rolled - then on the first throw, one sixth of the dice come up sixes - on the next throw, we roll only the remaining five sixths - and already nearly a third of our dice are showing sixes. If you did this for real, a few dozen tosses would suffice to get all of the dice to show up sixes...and that's the way it is with evolution. Each successful mutation pushes the 'design' of the creature a little closer to what we have today.
Evolution is not a theoretical thing. Take a disease like Turburculosis. Treat patients with whatever wonder drug you have - and almost all of them get better. But the mycobacterium that cause the disease EVOLVE - in each generation, just a tiny, tiny few of the bacteria somehow manage to survive the drug. The ones that survive have some kind of gene that lets them avoid the worst effects of the drug. Over years, the drug gradually loses it's effectiveness because the bacteria evolve to survive in it's presence. We can see this happen in the DNA of the bacteria - there is no magic, no mysterious 'designer' - it happens through simple, easy-to-understand mechanisms that are easy to study. The bacteria can evolve resistance to a particular drug over just a matter of years - it doesn't take millions or billions of years - it happens in no time flat. Evolution is a FAST process. Drug resistant diseases are very commonplace - and they result from evolution - pure and simple.
I don't believe watches are made by watchmakers because they're complex. I believe watches are made by watchmakers because a large number of people are glad to describe, in detail, how to make a watch. If God comes down here and announces on television that it was him who created Earth, I will believe in him. --Bowlhover03:53, 13 February 2007 (UTC)[reply]
Paley's argument does not depend at all on knowing how watches are made. It is made from the standpoint of one who can judge something as being more likely to be authored intelligently than not, even if they do not know for sure how or why it was made. I think you'll find that in most cases you'd be taking a pretty silly position if you couldn't believe in the intelligent authorship of a technical object without knowing exactly how it was made, or expecting someone else to. You can infer without too much difficulty in the technical world that intelligent authorship exists, which is part of the crux of Paley's argument. --140.247.242.7518:07, 13 February 2007 (UTC)[reply]
Well what I did was first I made the earth dodecahedral in shape and I placed continents on some of the pentagons of the dodecadhedron, you call them africa, north america, south america, europe, central asia, east asia, india, and antartica. I also drew some little islands and australia was an afterthought. Then I made the biggest mountains at the bondaries between the pentagons, that's were all the volcanos are as well. Then the pentagonal surfaces were distorted a bit to make the earth look rounder, I made the moon out of silver and the sun of gold. Are you listening? User:God.83.100.254.4011:55, 13 February 2007 (UTC)[reply]
In the book IRobot, by Issac Asimov, the robot QT uses logic to prove that he was created by god instead of by people, even though he saw that people could create robots, and that the earth didn't exist as he had never seen it:) This shows that logic could prove almost anything if you want it to:)Hidden secret 713:04, 13 February 2007 (UTC)[reply]
The problem with "intelligent design" is not that it is false, it is that it us unfalsifiable. A virtually identical argument could apply to any part of human scientific endeavor. Take fire for instance. Fire looks pretty scary and complicated. If all early people just threw up their hands and said "this is complicated, dangerous shit - God must have made it, let's just run away", we'd still be in the stone age. Or, disease. Just because it was not immediately obvious how pathogens could reproduce and transmit didn't mean it was the work of supernatural powers out of the realm of human understanding. Basically, the "god did it" theory is the most boring, overused excuse in the history of human nature. It's so boring I'm tired of writing about it. The only interesting part is that the intelligent design movement against evolution (and science in general) is a great example of a societal evolutionary effect. Eventually the united states will be so scientifically exhausted from generations of pseudo-scientific education that we'll be extinguised as a culture. --18.19.0.4119:24, 13 February 2007 (UTC)[reply]
Is there an overlap between rocks labelled flint and rocks labelled opal.
I'm specifically thinking of rocks found in association with chalk, sometimes in nodules with a white surface, dark gray/muddy brown with underlying colours or white/yellow/grey sometimes with graphite coloured dendritic structures.
I assumed flint but have seen in a minerology book similar rocks described as 'common opal' and 'dendritic opal' - it was not clear if they were found as nodules in the book.
I did a nice long search on this piece of trivia, and it turns out that it has been asked and answered with silliness, many times. The big bat caves of North America always seem to have counter-clockwise exit spirals, but nobody has systematically confirmed it with every cave. There was even an unreferenced suggestion that they have different directions in the north and south hemispheres, just like bathtubs! (not!). --Zeizmic01:11, 13 February 2007 (UTC)[reply]
The air in a cave tends to be at a different temperature than the air just outside. If this air is warmer than the outside air, it generates a thermal. One of the best ways for flying animals to gain altitude is to spiral around in a thermal -- and guess what happens if a swarm of bats don't all spiral around in the same direction? --Carnildo22:13, 13 February 2007 (UTC)[reply]
Gravitational effect of planetary size/density
This is sort of a theoretical question, but I can't find the appropriate articles on my own searches:
Assume a smaller planetary diameter than Earth (6300 km for example?);
Assume a roughly equivalent mass, and therefore gravity, compacted into that smaller area;
What, if any, known limits are there on planetary density/accretion/survival? Feel free to disregard the problems of having a core of sufficient density, although not anything related to angular momentum, loss of atmosphere, or other habitability.
Disregarding your disregard, it may be possible to have a planet made mostly from iron from a supernova, or possibly from lead, as ther are some lead stars who's main metal is lead, they tend to be very low in metals, and high in neutrons. What elements are there are converted by the s-process up through the periodic table, and the heavy elements decay back to lead.
Planets are formed from a stellar disk from points with slightly greater density than others, then snowball into larger and larger planets, sweeping up more and more with its growing gravitational field. Densities of planets can and do vary widely; the terrestials (Mercury-Mars) have a much greater density than the gas giants (Jupiter-Neptune), the fairly small variation in your "what-if" (a planet with a density about 1% more than Earth's) is easily feasible, say if the dust cloud that became our Sun had a tiny bit more iron instead of silicon. On formation, whether or not a planet forms in a particular orbit depends on where other planets have begun to form. A large mass like Jupiter will disrupt nearby planets, preventing them from forming, capturing them, or ejecting them (related to Clearing the neighbourhood).
The surface gravity of a planetary body plays a large role in determining whether it can hold on to an atmosphere. Beyond certain limits (determined by such things as the bodies relation to it's star and the amount of gas available), the planet will start trapping hydrogen and helium and grow into a gas giant. So for a given mass, decreasing its size will increase the probability that it will be able to retain a H/He envelope. However, if enough gas is available, it may then greatly increase in size by gobbling up gas, and in the process the net effect would be to decrease in density. So there is probably some upper limit on the density of an object that can form in a gas rich proto solar system. Aside from that, there is no physical limit on achievable density till you get much much denser and start seeing nuclear reactions. People and animals living on a planet with higher surface gravity would probably have thicker limbs and shorter heights to provide added support for their own weight. Dragons flight18:22, 13 February 2007 (UTC)[reply]
February 13
Sleepiness
I had a bad encounter with sleepiness in math class today. =( So, I went to the Sleep article to answer a few questions that I have about it, but it wasn't there. Anyway, here goes:
Is sleep mostly affected by the external or internal environment?
Can sleepiness or drowsiness be affected by conditions such as hot weather or cold weather? (today, it was snowing) What about climate?
Can drowsiness be affected by the clothes you wear?
Is sleepiness also affected by the tone of voice of the person your listening to? Will a monotonous monologue affect one's drowsiness? (eg boring teacher)
Is the position of the sleepy person affecting that person's drowsiness? Will sitting up make someone more awake, as opposed to someone resting on top of their desk? Or what about leaning back on the chair? Does this have to do with blood circulation?
No matter how hard someone tries to resist, can a person still go to sleep anyway? Is it some sort of involuntary action?
Lots. For women, the menstrual cycle can affect energy levels. Being dehydrated or low on oxygen can make one feel sleepy. Having a poor sleep the previous night can also do so. The frequency, quantity and components of diet can affect some people, i.e; some people get sleepy after a big meal, others when they go too long without eating. I personally find the weather a component, but snow does not personally affect me. Also personally, I find that my relationship to my own tiredness and environment makes a difference. For instance, if I don't want to be somewhere I get tired. If I tell myself what I'm experiencing is boring I get tired. If I tell myself that I'm sure to be tired because of some previous experience (lack of sleep, exertion, etc), I will be tired. Room temperature and lighting can make a difference. And finally and of course, health issues can make a difference; illness, nutrient deficiencies, etc. And BTW, I find that a) sitting up straight, b) taking deep breaths, c) doing eye rolls, d) drinking a big glass of icy water, and e) giving myself a pep talk and following 'energetic' thoughts helps keep me awake. A cup of coffee and a brisk walk help too. Good luck! Anchoress05:06, 13 February 2007 (UTC)[reply]
Sleepiness and falling asleep are clearly a function of a number of variables. OF COURSE a boring teacher speaking in a monotone about something boring will put you to sleep! If you didn't get enough sleep the night before, all the more so! If you ate fried chicken and mashed potatos and gravy and apple pie with ice cream for lunch and washed it down with a couple of beers, all the more so! If the lights are turned down low and you slump down in your chair and rest your eyes by closing them and it is warm in the room and other people are snoring, all the more so! Remedies: Sit up straight. Concentrate on how important it all is. Take detailed notes. Maintain eye contact with the speaker. Pinch or slap yourself every little bit and play a radio very loud and sing along with it (sorry that is more from having to stay awake while driving). Edison05:53, 13 February 2007 (UTC)[reply]
I find that I am more tired when it is too hot, or when I am not doing anything, so it seems the obvious answer is to force yourself to do something, then you will be more awake and able to do whatever it is you want to be awake for:) I also find taking something to college to eat during or between lessons helps:)Hidden secret 712:53, 13 February 2007 (UTC)[reply]
What happens when an oil pocket near a subduction zone is driven down into the earths core and reaches the molten iron?Or molten rock? It can't burn but does it explode?
Well, given the huge temperatures and pressures down there, it's likely that there will be some kind of chemical reaction - but it's not going to be 'burning' in the normal sense of the term. There would certainly be nothing left that looked anything like 'oil' long before it got deep enough to reach the molten core. Think about the coal seams being crushed into diamonds - these are drastic chemical and physical changes. SteveBaker23:44, 13 February 2007 (UTC)[reply]
When water flows out a faucet, the stream narrows on its way down. Why does this happen? Is it related to molecular bonding? pressure? density? - 72.81.251.19304:00, 13 February 2007 (UTC)[reply]
Don't quote me on this, I'm just a high school biology student. My understanding is that water molecules bond to each other due to slight hydrogen bonding between the oxygen and the hydrogen molecules.--Ed¿Cómo estás?04:11, 13 February 2007 (UTC)[reply]
Imagine what would happen if it didn't get thinner: the column of water would be coming out at of the tap with a radius of (say) 1 cm at a rate of (say) 10 cm of column per second, yielding 10πr2 == 10π cm3 of water per second. But now the column of water accelerates due to gravity to 20 cm of column per second, yielding 20π cm3 of water per second. Where did that extra water come from as the column descended? The only way to resolve this missing water problem is for the stream to get thinner, or break up into droplets or something. It doesn't break up (right away) due to water's hydrophyllic nature, as alluded to earlier. --TotoBaggins04:33, 13 February 2007 (UTC)[reply]
Remember occam's razor. Does the faucet in question have an aerator? Perhaps the copious air bubbles introduced are merely coming "out the sides" as it were. The water meets in the middle, because of it's surface tension. ToTo's explanation is completely correct, but may be less pronounced in the 40cm fall to the basin. tucker/rekcut22:25, 13 February 2007 (UTC)[reply]
Astronomy Question?
Have used your web site to try to find a few Astronomy questions I have had in the past. I was trying to find out more information about the Hertzsprung-Russell Aurora. Witch is a chart that tells you the magnitude in brightness of stars in the sky, from the Sun to the North star. I was shocked to see that when I did a internet search on the Hertzsprung-Russell Aurora. All I found was a web site to buy a 2007 Astronomical Calendar. Witch I already have in my bed room. Can you find out more information on the Hertzsprung-Russell Aurora for me and the many amateur Astronomers like me? Maybe you contact NASA to find out more information about this subject. I hope you can find out more information about the Hertzsprung-Russell Aurora, because I am curious about this subject.
...While a chart that shows you the brightness of the actual stars in the sky is called a star chart. There are some free ones linked from that page you might like to look at. You can quite see a lot with one of those and a pair of binoculars. Spiral Wave09:39, 13 February 2007 (UTC)[reply]
movie with atmospheric phenomenon?
I was interested in looking up the phenomenon featured in a movie, but now I can't remember what movie it was.
Two (male?) characters are talking at the bow of a ship, and they reach a point, probably not very well-traveled, when there's a high-pitched screeching noise. The shot goes to a view of the horizon, water and sky meeting, and the older and wiser of the characters has a name for it and describes it as the world being turned upside down.
I feel like it's in some sort of period, maybe fantasy action-adventure movie, and that the thing is called Somebody's something, although that last part might be wrong... Anyone?
This scene is from the 2005 film The Life Aquatic with Steve Zissou. As the title character is untying his shipmates after a pirate attack, Pele, blindfolded, asks "What is that sound? Is that...," to which Zissou replies "The Artctic Night-lights. Yeah. 'As if the natural world's been turned upside down.' - Lord Mandrake. Vikram, get some cutaways of this miracle."
Suppose by accident or by anchient or recent medical or legal text you discovered a chemical or virus or toxin or disease that was totally untraceable and acted over time or in a relatively short period of time according to the amount or frequency given then made friends with someone who was rich, got put in there will or became the sole inheritor of their fortune somehow and then did the deadly deed? Sounds like a murder mystery I know but with all the wonderous things that have occurred even before the founding of ancient Egypt, in the present day and most likely into the future is such an untracible, unknown death potion possible? (BTW... this question has nothing to do with the events surrounding Howard K. Stern.) 71.100.10.4807:04, 13 February 2007 (UTC)[reply]
There are many poisons. As any reader of detective fiction will know, there are some that are said to be untraceable. There are many more that are undetectable unless you know exactly what to test for.--Shantavira09:22, 13 February 2007 (UTC)[reply]
How about untraceable and undetectable with the knowledge thereof passed down from generation to generation and provided to only a very few special and secret elite? 71.100.10.4810:01, 13 February 2007 (UTC)[reply]
I know that taking in saturated fats will boost the level of both HDL and LDL levels (but more of the LDLs) and that'd raise our blood cholesterol levels. However, how do the saturated fats boost the lipoprotein levels?82.33.108.16909:24, 13 February 2007 (UTC)[reply]
tongue
you know we sometimes (in fact most of the time) get some white stuff on our tongues, and according to Chinese medical theories, more white stuff, means that yu are more sick or something, but what on earth is that, and does it really correlate with one's health?
82.33.108.16909:35, 13 February 2007 (UTC)[reply]
As far as I know that white stuff is a bacterial film that builds up over time. Though it can be something worse even a fungal infection. But for the most of us it's just a sign that we should spend more time performing oral hygene. 62.194.90.10710:17, 13 February 2007 (UTC)[reply]
Geographic tongue can sting and become quite painful. I cannot drink Sprite because it makes my whole tongue throb in pain. To my knowledge, there is nothing that can be done except stop eating and drinking when the geographic tongue pain flares up. --Kainaw(talk)18:49, 13 February 2007 (UTC)[reply]
A few biology related questions
I've been going to a bio paper where i don't have the answer key for most of the questions. There're a few questions where're i'm not too sure about the answer. They're all multiple choice questions, and i haven't included the answer options which i'm already sure is wrong. Much appreciated if anyone can help me out in any of these.
"Components of the cytoskeleton are: A) composed of subunits made of protein D) observed to coil and contract to cause cell movement." "A" looks like the more correct answer to me, but i'm not sure whether ALL components of the cytoskeleton are made from protein subunits. The cytoskeleton on a whole does cause cell movement, but i think saying the components of the cytoskeleton coil and contract to cause movement is wrong. Which is the correct answer?
The cytoskeleton is made of 3 filament types, actin, microtubules, and intermediate filaments. Actin is used in general locomotion, but only muscle cells have proper contractile units (though they are made partly of actin). The coil compressors are not found inside the cell, but in the ground substance. tucker/rekcut22:17, 13 February 2007 (UTC)[reply]
"The number of different enzymes in a generalized eukaryote cell, such as an Amoeba, may be as many as: A) 80 B) 400 C) 1000 D) 4000" I've got absolutely no clue about this one...
"Ethylene is released from: A) plant meristems B) flowers C) ripening fruit D) all of the above are correct" I know ripening fruit defintely makes ethylene, and plant meristems don't. But i don't know whether or not flowers release ethylene at all.
"In an experiment, auxin at a concentration of 1 part per million was applied to radish seedlings. Stem growth was found to be significantly stimulated. The roots likely showed B) stimulation, but greater than that of the stems C) inhibition D) apical dominance" The logical assumption would be that when the stems are stimulated, the roots would be inhibited. The thing is, I've always learnt the effects of Auxin in terms of when there's high or low concentration...and i really have no idea whether 1 part per million is considered "high concentration" or "low concentration" for auxin.
"The requirements of an animal for gas exchange increase as animals get larger because A) the ratio of its surface area to its volume gets larger C) they have more cells remote from the external environment. " Both should be correct reasons for why requirements of gas exchange are larger for big animals. But i'm not sure which would be considered the more 'significant' reason and therefore the 'most correct' answer. I'd go with C here, but i'd like to hear what anyone else has to say.
This question is, in my opinion, flawed. The classic answer is A, that as height increases by h, surface area increases by h squared and volume by h cubed, but this is why the circulatory and respiratory system evolved. In animals, the surface area of the lung alveoli can be calculated as having a (nearly) linear relationship to the lung displacement. As long as the cardiac output is great enough, adding more volume (of flesh to be perfused) is a matter of adding more parallel units (thus the number but not size of vessels, except perhaps for the few great vessels, is unchanged.) Of course, in very very large animals, this model breaks down, but it is because of the PRESSURES involved, and has little to do with surface area. The heart has to create such a high pressure in the aorta to have a reasonable differential across the capillaries that something gives. Of these two answers, though, C seems more wrong. All animals have circulatory systems capable of bringing nutrients to the deepest of tissues. tucker/rekcut22:17, 13 February 2007 (UTC)[reply]
C is right; A merely affects how hard it is for sufficient gas exchange to occur. The actual reason is the increased number of cells; I suppose they include the "remote" clause because they're counting only deliberate gas exchange and not that performed "automatically" at an interface. --Tardis17:28, 13 February 2007 (UTC)[reply]
"Haemoglobin is an efficient respiratory pigment in vertebrates because it A) is contained within red blood cells C) is able to form oxyhaemoglobin at high [O2] " Is haemoblogin contained within RBCs or just on RBCs? I had thought it was the latter, but if that's the case, the answer would be C (option B and option D were defintely wrong options) Option C doesn't sound right either - since it makes it sound like oxyhaemoglobin is only formed at high [O22], or is it?
The article says that it makes up 35% of the weight of a RBC, so it can't very well just be on the outside: remember that oxygen has no trouble going through cell membranes. So I think I'd go with A, although it's not clear that such containment is the reason it is efficient. I guess C is wrong with that reasoning too, though, since just oxidizing at high [O2] isn't going to make anything efficient. --Tardis17:28, 13 February 2007 (UTC)[reply]
Both (A) and (C) are correct statements, but only (C) is the reason that hemoglobin is an efficient respiratory pigment. A respiratory pigment should require a high O2 for oxidation, because that means at low O2 the oxygen will dissociate (making it available to low-oxygen-pressure tissues). See hemoglobin for a discussion of the hemoglobin saturation curve and cooperative binding. - Nunh-huh19:20, 13 February 2007 (UTC)[reply]
"Branching of cardiac muscle fibres in the wall of the heart enables A) differences in the speed of the spread of muscle excitation B) a stronger contaction C) a spread of excitation to all heart striated muscle D) a delay between atrial and ventricular contractions" IIRC, the purpose of the branching is so the heart (as a whole) contracts uniformally. Which isn't one of the options. I think the answer may be C, but i'm not sure whether or not the branching does enable a stronger contraction.
The heart does not contract as a unit, but in parts. The signal passes from SA to AV node, then (after the BoH) to the right and left bundle branches. These branches occur in the stream after the atria have contracted, so it can't be D, the action potential is all or nothing, and it's quality does not change the strength of contractions, so it's not B. C is true, the branches do help to propogate the signal, but they do not enable it, as they would contract even if the bundle branches were blocked (RBBB). These branches are most important because their configuration controls the timing of action potentials hitting the apices of the ventricles. tucker/rekcut22:17, 13 February 2007 (UTC)[reply]
"The three main functions of the circulatory system in animals are D) mass transport, transport of heat, and transmission of force" "D" was the correct answer based on the answer key. i'm not sure what the questions means when it says that a function of the circulatory system is to transmit force? what force?
"Consider the factors which affect the movement of water up a 50meter tall tree. The factors may be ranked from most important to least important as follows C) leaf transpiration, cohesion of water molecules, air pressure, capillarity". "C" is the correct answer per the answer key. Why would leaf transpiration a more important factor than cohesion of water molecules? And why is capillarity the least important? And on a side note, where do you guys think root pressure would rank?
Cohesion merely helps to transmit the force; it's transpiration that actually generates the osmotic pressures that pull the water. (Consider what would happen without transpiration at all.) Capillarity merely reduces the effective height of a tube. I'm not sure what you mean by "root pressure". --Tardis17:28, 13 February 2007 (UTC)[reply]
without getting too techy, DNA is made up of lots of nucleotides joined together. nucleotides are made of ribose sugar joined to a base and a phosphate group.
the carbons in the ribose sugar are numbered carbon-1 to carbon-5 (nucleotide has a nice picture. in the picture, 3' means carbon-3)
basically, when nucleotides join together, the phosphate group that's joined to carbon-5 of one nucleotide joins to carbon-3 of another nucleotide, making a chain of nuclotides that are joined together by phosphate links between their carbon-3 and carbon-5 atoms.
this means that one end of the DNA chain will have a nucleotide with it's carbon-3 not joined to another nucleotide (3' end), and the other end will have a nuclotide with the phosphate on it's carbon-5 not joined to another nuclotide (5' end) (see the second picture in DNA). --Dak19:07, 13 February 2007 (UTC)[reply]
AARUN S BAGH >>>> QUES about sex
can a woman be pregnant if a man inject his urine into her vagina?
I am sure you phrase your numerous questions carefully, and that you want an answer to the question you actually ask, so, yse, a woman CAN be pregnant under the specified condition. Especially if she were already pregnant. But it is not recommended to do this to a pregnant woman. Edison15:39, 13 February 2007 (UTC)[reply]
No. Blockage is almost always caused by either hair or grease. Bleach is ineffective against these. Use a chemical drain cleaner, and be extremely careful to exactly follow the instructions, as these chemicals are very dangerous. If you have a plunger or plumber's snake, try that first. -Arch dude15:59, 13 February 2007 (UTC)[reply]
But do NOT use drain cleaner if you have already poured bleach into the drain. That combination can generate large amounts of toxic chlorine or chloramine gas (depending on the type of drain cleaner), and poison you and your household. --mglg(talk)17:25, 13 February 2007 (UTC)[reply]
Note that one type of drain cleaner is indeed strong bleach. One common household alternative is machine washing powder - specifically the biological type is best. You might need to wait a bit though.87.102.66.14217:42, 13 February 2007 (UTC)[reply]
You should only use chemicals as a last resort, since (besides being generally unpleasant) they will cause damage/buildup in your drain that will lead to future blockages. The easiest and quickest way to clear a drain is to fill the sink with water, take a toilet plunger, give it three "pumping" plunges on the drain, and on the fourth stroke, pull the plunger all the way off the drain. Repeat as necessary. It may be helpful to stuff wet rags into any nearby drains so that the plunger pressure can't escape through them. --TotoBaggins17:54, 13 February 2007 (UTC)[reply]
I find it much easier to unblock a sink by removing the elbow in the p trap below the sink (it is very rare that a sink doesn't have one). That is where most of the clog is normally located and you can easily clean it out with nothing more than your fingers. --Kainaw(talk)18:46, 13 February 2007 (UTC)[reply]
Is there "virginfilia"?
There are many paraphilias explained in English wikipedia, but not one. What is called a person who has virgin fetish, or wants to have sex only with virgins, or who can not touch women that have been fucked by someone else? What causes this condition? Can you heal it? Thanks for your help! 193.167.45.24216:41, 13 February 2007 (UTC)[reply]
Doubtless it does exist, however Wikipedia is unable to give medical advice. If you are concerened about anything relating to medical or psycological health then the person to speak to is a doctor. --Neo17:54, 13 February 2007 (UTC)[reply]
Boric acid is also good for green - it's also available from pharmacists - but please note - not for a barbeque - adding odd chemicals to a fire used for cooking not a good idea. (Don't recommend borax as the sodium in it gives a yellow colour.)
Low sodium salt is a good choice - it will have sodium/potassium in.
For a red flame try a calcium compound - these are easy to get - calcium chloride is available as a road deicer (harware store), or calcium sulphate (plaster of paris).
Burning different gasses can make flames of different colours too. Hydrogen burns with an almost invisible flame, Butane burns with a blue flame, SteveBaker23:24, 13 February 2007 (UTC)[reply]
Astronauts Pills Part Deux
This is a re-visit from my question earlier. I read somewhere that there was a pill in which the Astronauts would have "sex" on their dreams while they are sleeping. And then some drug dealers in Cali got a hold of this drugs and were selling them on the streets. Has anyone heard of this story?
This is only my opinion, but I'm going to say that it's extremely unlikely. The reason being economics. No drug company (in my opinion) would create a potential goldmine like that and purposely restrict its use to 15 people a year. Anchoress18:36, 13 February 2007 (UTC)[reply]
Body part removal - least possible giblets left for survival
Anyone familiar with the many daily facts and quotes supplied to various sites may recognize this:
Even if the stomach, the spleen, 75% of the liver, 80% of the intestines, one kidney, one lung, and virtually every organ from the pelvic and groin area are removed, the human body can still survive.
I've been tasked with justifying this. To some small degree I can, organ by organ, understand it. But collectively? That's a lot to worry about; it would at least be very compromising. Any help out there? Wolfgangus18:45, 13 February 2007 (UTC)[reply]
Organs tend to be fairly independant in their functioning. I'd be concerned about the combination of stomach and intestines: at the very least, you'd need to be careful in what you eat: some sections of the intestines rely on food being pre-processed by the stomach or by other parts of the intestines. You might also have trouble keeping hydrated, without enough digestive tract to absorb water. --Carnildo22:35, 13 February 2007 (UTC)[reply]
Surrogates
Do sex surrogates really exist? If so, are they considered part of the AMA?
Hi
Hope you can help me? I have been trying to answer this question for a biology scenario and after a fruitless search I can't seem to word it in a way that makes sense. Thankyou for your time and any help will be appreciated.
'Briefly explain how the nerve supply to a skeletal muscle fibre causes it to contract? You may use a labelled diagram if necessary.
Does wearing a watch for almost 4 years non-stop restrict the growth of my wrists?
Okay, this is bizarre, but I just took my watch off for the first time in about 4 years - I wore it when I slept, during showers, everything. I seriously never took it off once. I put it on when I was 12 and I am 16 now. A lot of growing takes place in that time. People have noticed my wrists are pretty skinny for my size (6'5", 190 lbs). Is it possible that the watch restricted the growth of one of my wrists which also somehow restricted the growth of the other? Thanks! NIRVANA276422:09, 13 February 2007 (UTC)[reply]
Okay, this is a really bizarre confession, but at about your age, I was worried about exactly the same thing. If this were true, then you would expect that wearing small shoes would stop the growth of your feet, and so on. People have tried to stop parts of their bodies from growing, but they find it to be impossible, except by going through pain (eg. foot binding). Even if you could affect the growth of one wrist, there is no way it could be copied for the other one. I have skinny wrists, much smaller than either of my parents', but it is just genetic (probably from recessive genes or something). The Mad Echidna23:06, 13 February 2007 (UTC)[reply]
It is normal for bone structures to respond to stress. I have very small wrists until I was 19. That's when I started boxing. In a year, my hands and wrists widened. I haven't boxed in a good 10 years and my hands/wrists are smaller than they were when I boxed, but not as small as they were before. This is not unique to the wrists. For example, if you remove a tooth completely, the jawbone below the missing tooth will shrink. Like other and joints throughout the body, they weaken if not stressed in any way and strengthen if they are stressed (not to the point of fracture, of course). --Kainaw(talk)23:45, 13 February 2007 (UTC)[reply]
Hypnosis...?
Is it possible to hypnotize someone and then suggest to them that later after being exposed to a certain que that they fall into a deep sleep resembling a coma and to take such shallow breath they do not breath in enough air to stay alive or that their heart stops, etc.? (BTW... this question has nothing to do with the recent events surrounding Howard K. Stern.) 71.100.10.4822:51, 13 February 2007 (UTC)[reply]
No - definitely not. There is a great deal of debate over what Hypnotism is and how it works - but one thing is clear, you are only affecting what the person wishes to do. However, no matter how much you wish it, you cannot hold your breath long enough to cause harm because the autonomic systems take over breathing control once CO2 levels in the lungs get high enough. SteveBaker23:09, 13 February 2007 (UTC)[reply]
Formal common English plant names
Is there any convention about the capitalization of common English names for plants, used alongside the scientific binary names? For instance, which one is (most) correct: Smooth Rupturewort, Smooth rupturewort, smooth rupturewort? Thanks, — Kpalion(talk)23:34, 13 February 2007 (UTC)[reply]
xrays
okay i now this is homework but if some1 could point to the right topic then i can do the rest. I've done an experiment with x ray diffraction which were told the x-rays are at 2 frequency's and was wondering what an appropriate error in the wavelength would be. i can think to sources of error in the wavelength but i don't now how to quantify it. the two i thought of where the sources not quite emitting at the wavelength said, and the wave spreading between source and the crystal (ie wavelength L ends up being several waves over L-delta L and L+delta L, i assume we used soft xrays though not sure if that helps or is true wavelengths given where around 0.1-0.2nm--137.205.79.21823:53, 13 February 2007 (UTC)[reply]
