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April 13

Problem about capacitors in series

I don't seem to understand how capacitors can be connected in series. My question requires picturing a normal circuit diagram with two capacitors connceted in series with a cell. Now, I am rather puzzled with the fact that when you just connect the capacitors, you can get an ampere reading of say 2A between the two caps...I mean the Ammeter connected in series with the two caps except that you place it between them. Like II---A---II where the II is the cap symbol and A is the ammeter. I read in a book that capacitors arent supposed to pass any current between them. That's supposedly the point. But then, how come the Ampere reading. Upon searching in Google, I cam up with something about charges, but couldnt get the picture. I need to know because I am dying with curiosity.

If you are using alternate current than there will be a current going through the capacitor. There might also be some transient current even if the current is direct. Dauto (talk) 04:56, 13 April 2010 (UTC)

It is not true that capacitors can't pass current. It isn't possible for charged particles to move across the barrier, but when the amount of charge on one face of the capacitor changes, it produces an electric field that causes movement of charges on the other side, thereby inducing a current. Looie496 (talk) 05:07, 13 April 2010 (UTC)

If electricity in a wire is like water in a pipe, then a capacitor is like an impermeable elastic hshsghrt5hrseghsegtaehg

membrhgbdgdhgdtrhthutfr6htrhbrsane blocking the pipe. If you push the water in one direction with a constant pressure, the membrane will stretch until the restoring force balances the pressure, at which point the water flow will stop. The current on the far side of the membrane is always the same as the current on the near side, though—there's just a limit to how far the water can flow in total, for a given pressure. When the water is just sloshing back and forth (alternating current), there's no such limit because the membrane never stretches too far in either direction. -- BenRG (talk) 07:51, 13 April 2010 (UTC)

I like that analogy! One could extend it to explain the rules for capacitors in series and parallel, and to a warning about very high pressures (voltages) breaking the membrane. Dbfirs 08:29, 13 April 2010 (UTC)

Then you will love the Wikipedia article Hydraulic analogy. Cuddlyable3 (talk) 12:58, 13 April 2010 (UTC)

I did! It made very interesting reading. I've always thought of electricity intuitively in this way, but I've never thought of extending the analogy that far! Dbfirs 20:18, 14 April 2010 (UTC)

Wasp question (not about the insect)

Could anyone suggest some plausible reasons for a Wasp to suffer catastrophic failure? By "catastrophic" I mean severe enough to cause the engine to fail suddenly and completely during flight (as opposed to developing reduced power or gradually overheating) AND to require custom-made spares and/or a fully-equipped machine shop to repair. Any ideas, anyone? 24.23.197.43 (talk) 05:14, 13 April 2010 (UTC)

Bird strike (could it take out a piston engine?). Or Enemy Fire. Buddy431 (talk) 05:46, 13 April 2010 (UTC)

That didn't redirect to where I thought it would. I guess shooting is the closest I can find. That's really a pathetic article for an important topic. Buddy431 (talk) 05:48, 13 April 2010 (UTC)

The capitalization of "Fire" makes it a title (song title, in this case). However, Enemy fire is a redlink, I will redirect it to shooting. StuRat (talk) 09:45, 13 April 2010 (UTC)

Done. StuRat (talk) 09:45, 13 April 2010 (UTC)

Are you writing a novel or something? Avoid the word Catastrophic failure as in my book that means reduced to scape. Mechanical failure of some sort would be a good candidate. Components used in engines of that era where prone to fail unexpectedly. What you want is a failure that does not wreck the engine. A dropped vale in the cylinder head would cause the pilot to shut down the engine ASAP.

Here are a list of WASP engines photos on Wikimedia Commons.[1] There are lots of valves. Badly broken cylinder rings could be another - would cause a lot of dramatic smoke to trail from the aircraft etc., etc. A dropped valve would require the head to be removed and the old valve sleeve to be removed a new one pressed in, you need a workshop for that. From the photos I can’t tell if the valve would drop through into the cylinder but if it can, then that would damage the piston head a be a major repair job. Broken rings could score the cylinder walls and require regrinding as well as needing the piston to be removed. Again, you can’t do that sitting on the side of the tarmac. If its for a novel, then don’t get technical. Finally: I don’t know what year air worthiness certificates were introduced but the only need I have come across for a ‘custom made spare’ is when a script writer wants to get the message across to the audience that this is just another silly American B movie that lacks any credibility what's-so-ever; but if you must, here are some possible things that such an aircraft might be used for.--Aspro (talk) 08:00, 13 April 2010 (UTC)

I don't see anything wrong with giving details. Even if the audience doesn't understand them, they still "lend authenticity". As for a "custom spare", perhaps a component of the engine needs to be replaced, and no spare is readily available, so might be produced by a nearby machine shop ? This scenario might come up particularly during war, when getting the plane flying again may be critical and the normal delivery of spare parts may be interrupted by enemy action. StuRat (talk) 10:02, 13 April 2010 (UTC)

A brief comment as to why the component failed (say metal fatigue) is OK but there is that danger, that a technical explanation may lead the audience to think that this in depth information is going to turn out to be important, later on in the story. Indulge too often, and the audience can get lost with information overload. It is different for such shows as CSI: Crime Scene Investigation because there is always someone on hand, and at the right time, to ask the soppy questions, that give the investigators the opportunity to spell out for the audience, exactly how each factoid links together. However, if the OP was writing that sort of thing, he would already have the background knowledge to be able to do his own research in this area. Second point. For reasons of weight and performance, aircraft engines are built to very tight safety margins. Even in war time, critical engine parts, that might be held responsible for such a failure would be have been manufactured to such high quality standards, that it is unrealistic, that a workshop would have those engineering documents available to inform them how to do it. An airfield workshop would unlikely have suitable case hardening nor heat treatment ovens, and on so on, nor stocks of the right metal in that grade. If they need to case harden or heat treat a chisel etc., they would just use a forge. The engineer whipping off his leather belt and punching out of it a new washer for the lube system is a possibility, but that is the sort of thing that can be fixed easily and would not lead to a sudden catastrophic failure. The two conditions the OP requests thus exclude each outer, even for this era. --Aspro (talk) 11:52, 13 April 2010 (UTC)

Wrong fuel or sand in the fuel. Cuddlyable3 (talk) 13:05, 13 April 2010 (UTC)

Thank you all very much (especially Aspro). Yes, I'm planning to write a novel about a long-distance flight, and the particular scene with the engine failure is supposed to happen somewhere in Indonesia, and to lead into a comic scene where my heroine goes with a local trucker to get spares but the trucker drives so recklessly that they run off the road several times and end up having to make repairs to the truck as well. I think a dropped valve would be the best kind of engine failure in this case -- serious enough to make the engine fail at once and completely, but not so serious as to wreck it altogether. Plus, the engine would make a lot of dramatic-sounding noises at the moment of failure. (And yes, if the cylinder was one of the upward-pointing ones, then the valve would drop into the cylinder.) As far as "custom-made spares", my understanding is that they don't make Wasp engines or spares for them anymore, so any spare part that is specific to that engine and not just a generic engine spare would have to be made to order. Once again, thanks a lot to everyone, and clear skies to you! 24.23.197.43 (talk) 02:14, 14 April 2010 (UTC)

You could probably specify a broken valve spring - that would avoid the "dropping into the cylinder" thing - and it's likely that you could find a sufficiently similar spring (eg from a truck engine or something) to at least allow you to limp home. My problem is that this engine has a lot of cylinders and the failure of one valve wouldn't cause a total failure - just a loss of power. Just have the fuel line break...much more abrupt - and very certain to force a landing. Also more credible that you could find some replacement tubing. SteveBaker (talk) 18:49, 14 April 2010 (UTC)

generalising the pI = pH formula for situations where the opposing weak acid and base are of different concentrations

It dawned on me that a major shortcut for amine + carboxylic acid solutions of equal molarity was to treat them like an amino acid and therefore pH = pI = (pKa1 + pKa2) / 2. But what if they are of different concentrations? How would I modify the formula? Is there a way to "weight" the pKas? I'm guessing they wouldn't be weighted linearly? John Riemann Soong (talk) 06:54, 13 April 2010 (UTC)

Voltage Divider and a Wheatstone Bridge

The article on the wheatstone bridge uses the idea of a voltage divider to calculate the voltage across the bridge. But it seems to me that there's a problem with this approach. The equation for the voltage divider assumes that the current running through the two impedances is equal for both. However, if we consider, say, R₁ and R₂ to make a votage divider, then because there's a current across the bridge, the current across R₁ will not be the same as the current across R₂. So we can't use the voltage divider equation in this case. How, then, is the method describes in the wheatstone bridge article valid? 173.179.59.66 (talk) 08:07, 13 April 2010 (UTC)

The key point is that the position is adjusted so that the current through V_G is zero, then the current must be the same through R₁ as it is through R₂, because there is nowhere else for it to go. Think of current through (not across). Dbfirs 08:19, 13 April 2010 (UTC)

Except, from the article:

"If all four resistor values and the supply voltage ($V_{S}$) are known, the voltage across the bridge ($V_{G}$) can be found by working out the voltage from each potential divider and subtracting one from the other. The equation for this is:

$V_{G}={{R_{x}} \over {R_{3}+R_{x}}}V_{s}-{{R_{2}} \over {R_{1}+R_{2}}}V_{s}$

This can be simplified to:

$V_{G}=\left({{R_{x}} \over {R_{3}+R_{x}}}-{{R_{2}} \over {R_{1}+R_{2}}}\right)V_{s}$"

So it seems that there is a voltage across V_g, and hence a current. 173.179.59.66 (talk) 20:30, 13 April 2010 (UTC)

Er, not when the bridge is balanced (ie when the contents of tha braces equals zero) there aint.--BandUser (talk) 21:18, 13 April 2010 (UTC)

Try putting $V_{G}=0$ in your equation (the braces), and thus deriving the equation to find ${R_{x}}$: $R_{x}=(R_{2}/R_{1})\cdot R_{3}$ . Perhaps this needs to be spelled out in the article if it is being misunderstood. Dbfirs 21:48, 13 April 2010 (UTC)

From the article: "...if R1, R2, and R3 are known, but R2 is not adjustable, the voltage difference [ie V_g] across or current flow through the meter can be used to calculate the value of Rx...". So clearly, the formula presented above is used to calculate what the voltage across the bridge would be, whether or not it's balanced. Hence V_g isn't necessarily zero. 173.179.59.66 (talk) 23:08, 13 April 2010 (UTC)

This was an alternative for when the normal balancing procedure is not possible. The point of the normal balancing procedure is that it can give a very accurate result. I would question the accuracy of the "alternative" that you mention, but I haven't used it. (If you are not going to balance at all, then you might as well just use a multimeter!) Perhaps the article needs more explanation. Dbfirs 02:13, 14 April 2010 (UTC)

It's apparently a quicker method, because it's faster to read a voltmeter than to adjust a resistor. Regardless, my question still remains unaddressed: seeing as how V_g need not be zero (as the article, and hence the above formula, both assume), how is it that the approach used, that is, via voltage dividers, is valid? 173.179.59.66 (talk) 04:40, 14 April 2010 (UTC)

V_g, as a galvanometer, draws an extremely small current, so I assume that we are making a fairly accurate approximation. I have only ever used a Wheatstone Bridge in accurate mode, but I can see that for some applications, it might be more convenient to use the alternative, with good accuracy provided that the current through the galvanometer is extremely small. Our article doesn't explain how to apply the correction, but I'll leave this to an expert. Dbfirs 08:20, 14 April 2010 (UTC)

So if I understood correctly, the galvanometer will have a very high resistance to minimize the current lost, right? Originally I had thought that this must be true, but in an assigment I recently had, we were given the same layout as a Wheatstone bridge, except V_g was replaced by a regular resistor. We were then asked to find the current through this resistor. The problem is that, in the solutions, my teacher used the same method as above, by using voltage dividers. Is he wrong? 173.179.59.66 (talk) 08:32, 14 April 2010 (UTC)

No. Galvanometers are low resistance, very sensitive ammeters. For bridges with arms in hundreds of ohms region, you could take the galvo resistance to be effectively zero. I have never heard of using a bridge unbalanced for measurement of one of the arms. But if you wanted to do this I suggest using a high impedance voltmeter to measure the difference in voltage. This will draw effectively zero current and then you could work out the unknown resistor.

When you were asked to work out the current through the resistor, was the bridge balanced? If so, the answer would of course be zero. Hope this clarifies.--BandUser (talk) 17:21, 14 April 2010 (UTC)

(I think the usual arrangement is to use a galvanometer with a high series resistance to protect it, which makes it into a high impedance voltmeter if the resistance is known.) With the resistor in place of the galvanometer, I think you were just expected to use Kirchoff's circuit laws without the special Wheatstone Bridge equation that is only valid when the current through the galvanometer is zero. You might also like to read Network analysis (electrical circuits) for a general treatment. Dbfirs 19:47, 14 April 2010 (UTC)

No, the bridge was very specifically said not to be balanced. And yet, he used the voltage divider method above to get the voltage across the bridge, and divided that by the resistor value of the bridge (which was comparable to the value of the other resistors) to get the current. But from what I understand, this is a mistake, right? 173.179.59.66 (talk) 20:35, 14 April 2010 (UTC)

You could prove it wrong by applying Kirchoff's law to the currents (unless by some very strange coincidence the values chosen happen to give a correct answer from an incorrect method, but I can't find any values that would achieve this). The incorrect method gives a good approximation when the bridge resistance is large compared with the other four. Dbfirs 15:11, 15 April 2010 (UTC)

Plants - pinching new growth? pinching? really?

I'm new to this whole horticulture thing. I'm starting easy, with an avocado seed. It's got roots and I expect a shoot soon. I've read that if you don't want a 10 foot tall tree with 2 leaves at the top you should "pinch off" new growth every once in a while to encourage it to expand outwards rather than upwards. My question concerns the exact action - am I really just... cutting off the top of my plant? This seems rather barbaric. Is there a special way to cut it? 59.46.38.107 (talk) 09:14, 13 April 2010 (UTC)

Pinching is just that, taking your thumb and fingernail and nipping out the shoot. Wait until it gets to a manageable height and then take out the growing tip. If you're growing tomatoes, this process is called "stopping" and will result in more fruit. I've never grown an avocado so I can't vouch for it in this circumstance. This article [2] has more detail on the process and its results. --TammyMoet (talk) 09:49, 13 April 2010 (UTC)

Take note, the reason these jungle plants have a big seeds is so that they have the energy reserve to shoot up above the deep shade, given by the thick ground level foliage of the forest floor, until they reach sufficient light to sustain them further. It will bolt skywards given half a reason to. An indoor room give the same light level reading on a camera as the jungle floor. Pinch the top bud out as suggested. You could leave it outside during the day. As your new to this, set an alarm clock to ring in the early evening, so that you remember to bring it back inside, so as to avoid any frost damage. Avocados are cheap, so experiment. --Aspro (talk) 10:27, 13 April 2010 (UTC)

You don't need to lop off the entire top of the plant, all you need to do is eliminate the terminal buds (buds at the top/end of the seeding) by "pinching" them off. Let's say your avocado seedling is now a meter tall and growing straight up without branching. If you cut off the group of buds at the top of the seedling (at the end of the growing season) it will stop growing straight up next year . Instead the seeding will start sending branches off to the sides from a set of buds lower down the seeding (usually next to the leaves). These side branches will grow diagonally upwards the next season. When you think these side branches have grown high enough (2-3 meters?), you can then pinch or cut off the terminal buds of these branches. This process goes on and on and on until you have the tree with the high and form you want. The article "Pruning" may help. Sjschen (talk) 18:45, 13 April 2010 (UTC)

marine animals that have evolved from land animals.

Sir,Madam. I was thinking about the structure and movement of various marine animals, and got to wondering, is the upwards and downwards movement of the tail section of certain species whales and dolphins for instance, indicative of species that have returned from the land to the sea. bearing in mind the propensity of fish to move their tail sections from left to right. Yours Truly John Walshe.

I don't think that's a hard-and-fast rule, as there are marine animals not evolved from land animals which use the up-and-down motion, too, such as rays. There are also land animals, like snakes, which use a side-to-side motion. However, the up-and-down motion does facilitate sticking ones head (or just blow-hole) out of the water to breath, and only marine mammals need to do that, so there is some link. StuRat (talk) 11:06, 13 April 2010 (UTC)

I suppose the up-and-down motion of walking on land translates into up-and-down swimming in sea; the reason marine snakes, lizards and newts swim side-to-side like eels would then be that they crawl partly side-to-side on land as well. What about the ichthyosaurs, does anyone know how they swam? --91.148.159.4 (talk) 15:22, 13 April 2010 (UTC)

Considering that their tail fins were vertically oriented, I'd say it's much more likely that they used the fish style of side-to-side motion. Matt Deres (talk) 16:50, 13 April 2010 (UTC)

True. Well, I suppose this can be connected to the fact that they evolved not from dinosaurs (dinosaurs had developed the capacity to walk up-and-down pretty much like modern land mammals do), but from more archaic reptiles that presumably still crawled with partial side-to-side movement like lizards. Thus, one may say that while the implication "terrestrial origin -> walking -> up-and-down swimming" does exist, it only holds in those lineages where "proper" up-and-down walking has already been developed in the first place, and this took quite some time to develop in terrestrial animals. Penguins are another telling example - unlike ichthyosaurs, they do not originate from crawling reptiles but, ultimately, from walking ones (specifically from dinosaurs), so their swimming is primarily up-and-down oriented, as in marine mammals.--91.148.159.4 (talk) 18:42, 13 April 2010 (UTC)

Shrimp

The horizontally oriented tails of marine mammals developed from side-by-side hind legs, so there's a connection there. Fish on the other hand developed without any tie to what anatomy worked on land. Rckrone (talk) 17:46, 13 April 2010 (UTC)

Actually, looks like I'm wrong with regard to cetaceans and manatees whose tail fins are just tails. So scratch that. However, the Marine_mammal#Adaptations section touches on what 91.148.159.4 said about swimming and walking motions. Rckrone (talk) 17:58, 13 April 2010 (UTC)

Bear in mind that most "flat" fish evolved from bottom-feeding fish that habitually lay on their sides and whose eyes and various other body parts migrated to make that a permanent thing. Looked at like that, they are flapping their tails "from side to side" - but they are swimming on their sides so it looks like they are flapping up and down. SteveBaker (talk) 18:05, 13 April 2010 (UTC)

Dawkins addressed this very point in "Greatest Show on Earth" and he agrees with the premise suggested by the OP. it is the orientation of the mammalian spine that gives the up and down "galloping" motion in aquatic mammals. I think rays do not flex their spine up and down to swim, they use their laterals. And steve above is also correct. Also land snakes and lizards didn't evolve a mammalian spine so I don't see why the fact they walk side to side has anything to do with aquatic mammals. Another extremely interesting thing about land/sea migration is that it looks like some turtles/tortoises migrated from the sea to the land not just once but twice! Sea to land, back to sea and to land again! Including the ancestral fish to amphibian migration, that means they've been from sea to land three times! Vespine (talk) 22:29, 13 April 2010 (UTC)

Well the spine and the way of walking change together, one is a means for the other. But I don't think it's only a mammalian thing; as I said, I think that there are animals other than mammals that have adapted to swim, and that swim not laterally like fish, but mostly up-and-down. Penguins evolved from birds, which walk on land, and (swimming) shrimp evolved, perhaps, from bottom-walking crustaceans - although admittedly both seem to use their limbs more than fish and cetaceans usually do.--91.148.159.4 (talk) 22:57, 13 April 2010 (UTC)

Well that's exactly the point, penguins evolved to walk on land too but do not use their spine for swimming so they are a bit of an "inbetween" and shrimp don't have spines so they don't really count. I do agree with you that a spine which bends vertically is not THE definitive indicator of mammalian origins in an aquatic animal, but it is one of the very strong indicators. Along with things like lungs and bone structure. Vespine (talk) 00:20, 14 April 2010 (UTC)

Sure, no doubt about mammalian origins. The OP was about a connection between tail movement orientation and terrestrial origins in general, not only mammalian origins, so I was trying to say that the connection between walking and up-and-down swimming in a broad sense may hold not only in mammals. I'm conjecturing that dinosaurs' and birds' spines have also become sufficiently re-oriented to make vertical oscillation easier than lateral one. Of course, I could be wrong - I don't understand the underlying anatomy well enough, and I don't really have examples: it's true that penguins don't seem to rotate their bodies for swimming very much anyway, so it may have been too far-fetched of me to draw them into the picture. On the other hand, there may be some examples with swimmers that have a background as sea-bottom walkers: for example lobsters swim by flipping their tails up and down more or less like marine mammals (source in hidden text). Shrimp and crayfish use limb-like structures, but they also flip their tails like lobsters ((source in hidden text)). The flat ends of their tails are also horizontally flat, as in marine mammals. --91.148.159.4 (talk) 14:25, 14 April 2010 (UTC)

Primaeval woodland in the UK

Is there are woodland or forest left in the UK that is truely wild and has never ever been planted or cultivated? Even ancient woodlands such as the New Forest were planted centuries ago. Thanks 78.147.232.11 (talk) 12:25, 13 April 2010 (UTC)

According to episode three Man Made Britain of Britain From Above - which I've just (20 minutes ago) watched - the answer is pretty much no. Mitch Ames (talk) 13:51, 13 April 2010 (UTC)

Depends what you mean by "never ever been planted or cultivated". The wood at the bottom of my garden (Brandon Wood, Warwickshire) is an ancient woodland, mentioned as such in the Doomsday Book. But no tree in there seems to be more than about 150 years old. This could be because the trees have been harvested over the ages, and that might mean the woodland has been "cultivated". Also a woodland which contains pollards - that has been "cultivated", but it could date from "time immemorial". I beg to differ with Mitch, however, in that the Caledonian forest seems to be a remnant of the post-glacial coniferous forest which covered the British Isles after the last Ice Age. --TammyMoet (talk) 15:22, 13 April 2010 (UTC)

Caledonian Forest 89.240.34.241 (talk) 22:34, 13 April 2010 (UTC)

In a case like this, I wonder how great a role something like the Little Ice Age can play in skewing the results. I'm not a climatologist, but it seems to me that you'd have a hard time finding a section of forest that had existed continually for, say, a thousand years when you have temperature changes that great, lasting for so long. Matt Deres (talk) 16:44, 13 April 2010 (UTC)

300 years is a blink of an eye when talking about great trees such as oaks! --TammyMoet (talk) 19:07, 13 April 2010 (UTC)

Not if it gets so cold that it causes the tree to die or even if the climate shift is enough to curtail the growth of saplings in favour of more cold-hardy species. More philosophically, there's the possibility of a variation of the "Ship of Theseus" - is it still the same forest if the oaks survive, but the beeches and poplars are replaced with, say, birches and evergreens? Matt Deres (talk) 20:20, 13 April 2010 (UTC)

I've seen numerous oaks younger than that develop rot to the center and basically die of old age. Edison (talk) 16:14, 14 April 2010 (UTC)

What I should have said was, is there any land in the UK that has never been cultivated, managed, or planted? Unless its bare rock, its probably going to be a forest, climax community and all that. I understand that Britain would naturally be covered in wild forest but at various times all of it (or nearly all?) has been cultivated or cleared by man. 89.240.34.241 (talk) 21:32, 13 April 2010 (UTC)

Places such as Rothiemurchus, Abernethy and Glen Affric are remnants of the Caledonian Forest of which according to our article only 1% remains (but that 1% should fit your requirement).213.160.108.26 (talk) 22:25, 14 April 2010 (UTC)

The previous answers are correct, there is even much debate as to whether or not the UK was ever even entirely forested. Before we arrived on the scene there would have been plenty of herbivores (like elephants) that would have knocked down trees and probably maintained grassland/savannah. The most ancient woodland left is probably Hatfield Forest (go there now and there are no planes flying overhead into Stansted Airport!), Westonbirt Arboretum apparently contains a ring of genetically identical trees that are thousands of years old and may be a relic of the primaeval woodland you refer to. 131.111.30.21 (talk) 10:36, 17 April 2010 (UTC)

I had imagined that the elephants and hippos and so on would have been before the various ice ages, when the glaciers covered most or all of Britain. Presumably after the last ice age, Britain was covered in forest, and people eventually migrated here. I find it surprising that all of Britain has been cleared by humans - there were not many humans in past ages, and they must have worked really hard. I presume they used slash-and-burn farming techniques that I think are still used in the Amazon area. 78.146.229.142 (talk) 12:02, 17 April 2010 (UTC)

Gravity, friction and mass.

Would you please explain what is conflict in my logic based on my understanding of the laws of physics between statement number 1 and statement number 2. I suspect my knowledge of physics is flawed and I would welcome guidance.

Statement 1.

Two bodies(say a sphere) of identical size and shape are dropped at the same time from the same height. One sphere is filled with lead and the other sphere is filled with feathers. Both spheres will hit the ground at the same time.

Statement 2.

The same two spheres are each placed on identical skateboards and set off at the same time down an identical slope. The sphere filled with lead will pass the sphere filled with feathers.

If gravity is a constant accelerating force what is the explanation for the outcome of statement number 2 ?

Thank you.

86.12.198.101 (talk) 14:44, 13 April 2010 (UTC)

That's so easy. The coefficient of friction is not the same for every force applied. This is obvious if you think about what happens when you try to push with your pinkie a balloon versus a lead ballast of the same shape. In an "idealized" environment (where the physicist assumes zero friction) you can push each of them just as easily. Or maybe not, since they have inertia. What do I know, I'm just a useless hack. 84.153.214.140 (talk) 14:58, 13 April 2010 (UTC)

Statement 1 is true in an idealized setting without air resistance or other friction. Statement 2 is false in this setting (with no friction, the skateboard will behave like a sled - but see below).

Statement 2 is true in most realistic settings with friction.

However, there is an idealized setting in which both are true: No air resistance and rolling resistance, but perfect friction between skateboard wheels and slope. In this case, the potential energy of the system (proportional to the mass of the skateboard and the sphere) is converted into kinetic energy (corresponding to forward motion and proportional to the mass of the system) and rotational energy of the skateboard wheels (which is independent of the weight of the system). In the heavier system you need a smaller proportion of energy to make the wheels spin, so a larger part is kinetic energy, hence it goes faster. --Stephan Schulz (talk) 15:05, 13 April 2010 (UTC)

(edit conflict) Statement 1 is only true in vacuum. Otherwise air resistance will have an effect. For substances with such different densities as lead and feathers, air resistance will be a significant factor. In Statement 2 air resistance will have an even bigger effect, as the effective force acting on each skateboard and sphere parallel to the slope is less than its weight; it is weight x sin(θ) where θ is the angle between the slope and the horizontal. Gandalf61 (talk) 15:08, 13 April 2010 (UTC)

The problem here is that the two parts of the question make different kinds of assumptions. In effect, we have a spherical cow and a goat-shaped goat. In the first case, the questioner has seen fit to ignore the effects of air resistance - which would otherwise result in the lead ball hitting the ground before the feather-filled ball. But in the second case, friction with the track and between the axles and the wheels has not been ignored, because if it had then both skateboards would arrive at the end of the track at the same time. So this is really an issue of missing/unstated assumptions. If we were told (for example) that these two experiments were being carried out on the moon (no air resistance - but plenty of friction) then we might reasonably understand what the questioner had in mind...but without that context, we don't know what we're supposed to ignore and what we required to take into account.

The question is greatly confused by the fact that we're specifically told that the feathers are packed into a ball the exact size and shape of the lead ball. If we're supposed to be ignoring air resistance then why bother saying that? The usual assumption in this kind of question is that if such details are stated, then they are relevant. SteveBaker (talk) 17:48, 13 April 2010 (UTC)

Not quite, see my comment above. There is a reasonable abstraction (no friction, no air-resistance, but perfect no-slip wheels of finite moment of inertia) where you can have this result. --Stephan Schulz (talk) 18:13, 13 April 2010 (UTC)

Its like rolling two cylinders down an inclined plane, only this time it's the skateboard wheels that are absorbing the energy. The same thing would happen on the moon, so air resistance isn’t the prime factor.--Aspro (talk) 18:22, 13 April 2010 (UTC)

... and if you take the spheres off the skateboards and just roll them down the slope, then the lead sphere will still win (assuming the spherical shell is more dense than the feathers). There was a similar question on an Oxford Entrance examination in the 1960s. If you want the feathers to win, then you have to put less lead inside the other sphere and suspend it at the centre with light spokes. Dbfirs 21:12, 13 April 2010 (UTC)

Oxford Entrance examination of the 1960s??? Are these practical experiments preformed any more? I have read, just this month, that the modern school system only trains pupils to pass exams, instead of providing an education. There are many questions asked 'here' which seem to confirm that education (and the insight that it can provide) is a thing of the past. Can we get these school fees reimbursed? They have not delivered the goods.--Aspro (talk) 21:59, 13 April 2010 (UTC)

BTW: Just to be fully correct, the lead ball will hit the ground (slightly) before the feather one. It is not true that everything falls at the same speed, but rather it is approximately true. On earth the difference is not measurable, but it is there. To the OP: do not let this confuse you - most of the time the approximation is correct and should be used. Ariel. (talk) 02:40, 14 April 2010 (UTC)

I think I know why you think think that, and if yes, I had a major discussion with my high-school teacher about it. Both bodies are attracted towards the common center of mass, and the heaver ball makes the Earth move faster...right? Or wrong? --Stephan Schulz (talk) 07:40, 14 April 2010 (UTC)

Well, let's be a little careful about that. He who lives by the nit-pick must also die by the nit-pick! We know that $F=G{\frac {m_{1}m_{2}}{r^{2}}}$ - the force exerted on each body (both the ball and the earth) is proportional to the product of the two masses. However, the acceleration due to that force is given by A = F / m ...and the acceleration is what we care about here. So the acceleration of the ball depends only on the mass of the earth because its own mass cancels out...and the same is true of the acceleration of the planet...it depends only on the mass of the ball. So yes, the earth does move by the most microscopic amount imaginable in the direction of the ball due to the balls' own (insanely puny) gravitational field. If you drop the lead ball, it'll hit the ground a vanishingly small amount of time sooner than if you had dropped the feathery ball. But (and this is the point where your nit-pick fails!) if you drop both balls at the same time (as this experiment stipulates) - then even at this microscopic level of nit-picking, they still land together since the earth is being accelerated simultaneously by both balls. (Unless you drop the balls on opposite sides of the planet or something - but then our uber-nit-picker would invoke relativity and we'd have to ask what "simultaneous release" means for widely separated objects moving in different directions.) The balls themselves both experience the exact same accelerations. But in any case, the numbers involved are vastly too small to matter and I strongly urge our OP to studiously ignore this part of the thread because it's very, very, silly! SteveBaker (talk) 18:42, 14 April 2010 (UTC)

Homosexuality and Pedophilia

Hello, I don't want to do politics, so please don't do either, I was just wondering if there are any studies inverstigating links or relations between homosexuality and pedophilia. Again, no polemics, no political (in)correctness, just studies, please. Thank you very much. --Lorem ipsum dolor sit amet (talk) 18:00, 13 April 2010 (UTC)

Yes. This review article from 2007 should contain some relevant references. --NorwegianBlue ^talk 18:48, 13 April 2010 (UTC)

To clarify, this link is about childhood victims of homosexual paedophilia becoming homosexuals as adults, not about homosexuals being likely to commit paedophiliac acts (I'm clarifying, because there were some recent questions about the latter in connection to a statement by some papal spokesman).--91.148.159.4 (talk) 19:01, 13 April 2010 (UTC)

Not a study but I shall contribute a logical argument: how could homosexuality be any more related to pedophilia than various fetishes, such as shoe fetish, or even heterosexuality? Pedophilia itself is a sexual orientation, just like verious fetishes.--92.251.147.169 (talk) 18:51, 13 April 2010 (UTC)

See yesterday's thread at Wikipedia:Reference Desk/Humanities#Homosexuality = Paedophilia? Studies?. Comet Tuttle (talk) 20:23, 13 April 2010 (UTC)

Is pedophilia normal?--79.76.163.157 (talk) 23:18, 13 April 2010 (UTC)

What do you think? Look up the definition of "normal" and try to fit paedophilia into any of those definitions. I'll be surprised if you are left with any ambiguity after this exercise. Vespine (talk) 00:23, 14 April 2010 (UTC)

I detect that are implying that the answer is clearly abnormal, however it depends on the definition you take. Here are two, from WordWeb v5.0:

1. (psychology) being approximately average or within certain limits in e.g. intelligence and development - this make both homosexuality and pedophilia abnormal

2. In accordance with scientific laws - this makes both homosexuality and pedophilia normal

Abnormality says nothing about the potential harm to individuals nor what remedies (e.g. convince society that homosexuality is acceptable vs aversion therapy for homosexuals) are appropriate. An IQ of 150 is abnormal. It says nothing useful. 78.148.114.247 (talk) 00:56, 14 April 2010 (UTC)

Well, no, you're arguing semantics, I specifically said to look up the various definitions. Normal can also mean "(of a solution) containing one equivalent weight of the constituent in question in one litre of solution." but it's hardly relevant, just like "in accordance to scientific laws" is not relevant in this context either. dictionary.com normal has that definition at 4(b) of natural occurrence. google normal does not even have that definition. If the question was "is a society with paedophiles normal?" I'd say you might have an argument, but is being a paedophile normal? I think is clear cut. Vespine (talk) 01:23, 14 April 2010 (UTC)

Well if you use the definition "of natural occurrence" (is being a paedophile a/of natural occurence) then perhaps although it depends what you mean by 'natural occurrence'. If you mean innate then I think the answer is may be. As we've discussed many times before on the RD, the word natural is very fussy and it would seem difficult to argue conclusively any behaviour that occurs isn't natural. Well unless you believe in God and/or the devil in which case you could certain behaviours only come from God and/or the devil and these aren't natural but that isn't a particularly scientific answer. Nil Einne (talk) 01:58, 14 April 2010 (UTC)

Is being a homosexual normal? 78.148.114.247 (talk) 01:53, 14 April 2010 (UTC)

This is the science reference desk. We can talk about probabilities and perhaps evolutionary causes and maybe even biochemical and/or genetic causes. But words like "natural" and "normal" are not things that science can help you with. They are terms without solid meanings. We can't perform some kind of scientific test for "natural-ness" or "normality". This is a matter for society to decide. This question belongs on the "humanities" reference desk - and it's already been asked there. So unless someone can answer the actual question we've actually been asked ("Are there any studies relating these two facets of human behavior?") let's end this thread and direct readers and contributors to the correct place to discuss it. SteveBaker (talk) 02:07, 14 April 2010 (UTC)

Actually, true pedophiles (those whose primary sexual interest is prepubescent children) often don't prefer one gender over the other. It's the fact that a child IS A CHILD that attracts them. They are attracted to the way children look (i.e., the lack of adult secondary sexual characteristics is what turns them on) and think. Most pedophiles find some children more attractive than others, but what makes a particular child special may have as much to do with age and physical characteristics as with gender. Like people of more acceptable sexual orientations, a pedophile may have a "type." Gentlemen prefer blondes, women like guys who are tall/dark/handsome, and so forth - that doesn't mean that "preferring blond women" is a sexual orientation in its own right or anything other than an individual preference. An adult who chooses to act on an attraction to a person whose body is sexually mature but who is below the age of consent is another matter. Male homosexual culture, probably even more than our culture already does, idolize the beauty of youth, and as homosexuals are already existing for the most part outside of mainstream society, it may be easier for them to ignore the taboo on sexual involvement with a minor. So there may be cultural link or relation between homosexuality and sexual involvement with post-pubescent minors, but actual sexual involvement is a behavior. Attraction is involuntary, and although culture has an influence, biology is a huge factor in attraction. Are gay men more turned on by teenage boys than straight men are by teenage girls (whether either of them admit to or act on that attraction or not)? I doubt it. 71.104.119.240 (talk) 06:31, 14 April 2010 (UTC)

• Vatican Statement Regarding Comments by Card. Bertone
  • Interview with Scicluna --88.66.204.235 (talk) 17:12, 14 April 2010 (UTC)

Of course by definition, no perversions are normal. Maybe thats how we define perversions. Some perversions are legal (eg homosexuality), some are not (eg pedophilia). Other countries have different rules. Lawsin different countries are somewhat arbitrary. Morals are something defined by the religion you follow.--BandUser (talk) 00:09, 15 April 2010 (UTC)

It looks like your definition of 'perversion' is arbitrary too. And I think you'll find that morals are not solely defined by religion. AlexTiefling (talk) 14:18, 16 April 2010 (UTC)

Making my own tubular steel shelving in needed dimensions

I like this shelf but its dimensions render it inapplicable to my situation. I could buy some tubular steel or aluminium, but then what - how would I attach the ends to a plate in a way that didn't look messy? I'd like something that looks similar to the one in that picture (all-metal). I have a soldering iron and a weird little handheld butane thing I bought years ago and lost the instructions for - I remember it said something about brazing. Also, there are some putty things available where you mix two putties together and they react and harden after a period to a metal sort of bond (for fixing pipes etc). Anyone got any suggestions? --78.148.114.247 (talk) 22:18, 13 April 2010 (UTC)

You didn't link to a picture - so it's hard to guess what you have in mind. Soldering or brazing steel or aluminium tubing is a difficult and skilled process. You might want to consider using screw-fit plumbing fittings - then spray-paint it matte black or something. Take a trip to the plumbing section of your local DIY store and you'll be sure to find ready-made parts that can basically be screwed or even epoxied together to make a stiff framework - you'll even find parts that would be useful for feet and other bits and pieces. The "putty" stuff you are thinking of is called "Epoxy putty" - and that might well be all you need. If you are really itching to use the butane torch, you'd want the kind of copper plumbing fittings that have solder already applied inside the joints. That would be a much easier way to connect copper tubing - but it's not suitable (or even available) for steel or aluminium tubing. SteveBaker (talk) 23:37, 13 April 2010 (UTC)

Oh, right, thanks here is the image. I'd like it in this matt aluminium/steel finish. One possibility might be to cut off one of the sections with a multitool and then use a grinding wheel to neaten it? Most of all, I like this particularly cheap one but I can fathom no way that this would look neat after I had attacked it with a multitool. 78.148.114.247 (talk) 23:51, 13 April 2010 (UTC)

Ah - I see. Well, in the case of the one on eBay, instead of cutting off the tube that runs along the front edge of the shelf (leaving ugly, raw cut edges on the front ends of the support tubes). I would cut off the last tube at the BACK of the pipe and relocate the brackets forward one row...but everything depends on how those brackets are fixed. If they are just screwed into place - then it's easy - but if they are welded or molded on there - that wouldn't work. SteveBaker (talk) 02:22, 14 April 2010 (UTC)

Two methods:

• Buy the tubes, and flat metal for the sides, then connect them by buying long threaded dowels. Drill holes in the flat metal, put the dowels through the tubes and metal, then attach a nut on each side and tighten. Then use your multitool to trim the dowel right down to the nut. For extra reliability buy loctite threadlocker, use blue if you plan to take it apart or red if you want it permanent.

• Get short wooden dowels exactly the size of the inside of the pipe. If necessary make them using a hole saw. About 2 inches long. Glue them to the side metal, then glue the pipes onto them. For extra strength drill a hole in the metal and put a wood screw (sheet metal actually - you want a flat bottom on the head, not a cone like a typical wood screw) through the metal and into the wood.

Ariel. (talk) 02:31, 14 April 2010 (UTC)

April 14

Pressure

What is the general direction of a low pressure center as it moves across the US? Lamb99 (talk) 00:58, 14 April 2010 (UTC)

The trade winds in the US blow from west to east. As a side note weather forecasts in the US are more accurate further from the west coast because of this. Ariel. (talk) 02:44, 14 April 2010 (UTC)

They are called westerlies. The trade winds go from east to west and are over the tropics. Dauto (talk) 03:01, 14 April 2010 (UTC)

The term Ariel was trying to think of was prevailing winds. The trade winds and the westerlies are two instances of prevailing winds. --Anonymous, 05:15 UTC, April 14, 2010.

Hmm, and the map in those articles makes it look as though the trade winds do blow in the US. I've added a comment to the trade winds talk page. --Anonymous, 05:40 UTC, April 14, 2010.

Strong low pressure systems over the US can also travel northward due to ridging within its warm sector, southward due to cold Arctic air, or even retrograde westward in a counter-clockwise loop. We've seen all three of those this year, satellite archives here. ~AH1^(TCU) 23:42, 14 April 2010 (UTC)

Research influenced by funding source

I frequently read about research studies sponsored by companies or industries with a special interest, in which the conclusions of the study invariably support the position of the sponsor. A recent example that comes to mind is the FDA's 2008 finding that bisphenol A in plastics is perfectly safe, citing chemical industry studies while ignoring independent research that reached other conclusions.

What is this phenomenon called, where the conclusions of a study are pre-biased according to the sponsor's interests? I thought there might be an article on it somewhere, but all I can find is one sentence in Selection bias#Related issues. ~Amatulić (talk) 05:28, 14 April 2010 (UTC)

In general, that type of thing is called a conflict of interest. Note that the lab may do everything legit, but the company hiring them can still twist the results, by suppressing info found contrary to their business interests and highly publicizing info helpful to their business. To do this, they require the lab to sign a nondisclosure agreement before they are funded, which states that any info learned belongs to the funding company, and the lab has no right to release it independently. The same company might fund many studies at several labs, and pick and choose to find those that support their position. StuRat (talk) 05:36, 14 April 2010 (UTC)

As someone from the other side of the pond, I find it astonishing how often government decisions are the result of influence by commericial interests, rather than the public good. 89.242.91.98 (talk) 09:38, 14 April 2010 (UTC)

Are you sure it doesn't happen there, too ? StuRat (talk) 14:50, 15 April 2010 (UTC)

Research has shown that people are unaware of the factors that affect their decisions. I recommend Influence: Science and Practice for everyone. To the point, even if everything is on the up and up researchers will still be affected by their sponsors, but they may genuinely deny it. It's human nature. Imagine Reason (talk) 14:21, 14 April 2010 (UTC)

I detect a conspiracy, since your link is now a redlink. :-) StuRat (talk) 14:49, 15 April 2010 (UTC)

The specific question of the FDA (and other agencies) is often referred to as regulatory capture. --Mr.98 (talk) 14:33, 14 April 2010 (UTC)

Interesting replies, but not quite what I'm looking for. Doing some googling, the correct term appears to be "funding bias". Since such an article doesn't exist on Wikipedia, maybe I'll write one sometime.

I found some academic papers using this term, although the most accessible is this economist's blog article, which uses more specific terms "funding outcome bias" and "funding publication bias":

Anders Sandberg (2007-01-14). "Supping with the Devil". OvercomingBias.

Also, this paper on funding bias related to health effects on cell phone use doesn't any term to describe the phenomenon, although it refers to another paper that uses the term "sponsorship bias". ~Amatulić (talk) 18:20, 14 April 2010 (UTC)

Another source of bias is coming to a conclusion prior to examining the data, then using data evidence to support that pre-stated conclusion. This method is technically not science. ~AH1^(TCU) 23:48, 14 April 2010 (UTC)

I agree that approaching a study with a bias can be a problem, but not if it's a double-blind study with only objective measures. In such a scenario, there's no method by which the researchers can bias the data to support a given conclusion. Say they have a cholesterol lowering drug (or that this is what they want to conclude). If they take blind blood samples, send them to a lab for cholesterol counts, administer the drug, then repeat the blood tests, there's no opportunity for them to mess with the data. Any subjective measures, on the other hand, like determining if an anti-acne med works by "counting and classifying the severity of pimples" would likely fall prey to such bias. Also, if the researchers have the opportunity to throw out "bad data", this process can be highly subjective. StuRat (talk) 14:58, 15 April 2010 (UTC)

Metal in the microwave?

The microwave in my house has a metal rack in it, in the chamber where the food cooks. How does this work without doing damage? I've brushed my hand on the rack after the microwave had been running for ten minutes or so, and it was hot, but not nearly so hot as a spoon I left in the microwave for two or three minutes. Is this some special kind of metal? Please explain! 71.104.119.240 (talk) 05:54, 14 April 2010 (UTC)

I found patent #4455467 which talks about it. It seems that the rack is designed to try to hide in the cold spots of the microwave, but also that the rack is simply large enough to absorb the heat. Ariel. (talk) 09:11, 14 April 2010 (UTC)

Thank you! I wouldn't have thought that it was safer to put a big rack in the microwave than a spoon or a bit of foil, but I guess it makes sense that smaller items can't absorb the heat. (I guess that explains why I've known a few spoons to survive microwave cooking, whereas a thin foil wrapper on a stick of butter bursts into flame immediately - according to my roommate who tried to melt the butter with the wrapper on.) 71.104.119.240 (talk) 07:56, 15 April 2010 (UTC)

IIT QUESTION

A LARGE FLASK FITTED WITH A STOP COCK IS EVACUATED AND WEIGHED, ITS MASS WAS FOUND TO BE 134.57gm. IT IS THEN FILLED TO A PRESSURE OF 735mm AND THEN RE-WEIGHED , ITS MASS IS FOUND TO BE 137.456gm THE FLASK IS THEN FILLED WITH WATER AND WEIGHED AGAIN, ITS MASS IS NOW 1067.9gm. ASSUMING IT IS AN IDEAL GAS CALCULATE MOLECULAR MASS OF GAS.

    FORMULAE THAT COULD BE USED IS OF A REAL GAS EQUATION i.e :-
    
                    PV=RnT
         where:- P = PRESSURE
                 V = VOLUME
                 R = CONSTANT[0.0821]
                 n = NO. OF MOLES
                 T = TEMPERATURE
—Preceding unsigned comment added by 122.173.31.193 (talk) 06:17, 14 April 2010 (UTC) 

Please don't use all caps. StuRat (talk) 06:20, 14 April 2010 (UTC)

Please do your own homework.

Welcome to the Wikipedia Reference Desk. Your question appears to be a homework question. I apologize if this is a misinterpretation, but it is our aim here not to do people's homework for them, but to merely aid them in doing it themselves. Letting someone else do your homework does not help you learn nearly as much as doing it yourself. Please attempt to solve the problem or answer the question yourself first. If you need help with a specific part of your homework, feel free to tell us where you are stuck and ask for help. If you need help grasping the concept of a problem, by all means let us know.:StuRat (talk) 06:20, 14 April 2010 (UTC)

As a hint, you're given the pressure, you can get the volume from the amount of water and the density of water, and you've probably been told the temperature (or can assume room temperature). You can now solve for the number of moles. With this and the mass of the gas, you can calculate the molecular (molar) mass. Good luck. -- 140.142.20.229 (talk) 20:43, 14 April 2010 (UTC)

Even harmonics in Electrical power lines

It is generally said that only ODD harmonics are present in electrical supplyand odd harmonics are only dealt with -- My question is "Why EVEN harmonics are not present OR why it is not a problematic issue? —Preceding unsigned comment added by 170.38.136.2 (talk) 06:21, 14 April 2010 (UTC)

That's not a generally true statement. Harmonics are typically caused by some type of distortion; certain types of distortion favor amplification of even or odd harmonics. For example, see Triangle wave vs. Square wave to compare the frequency spectra. If your distortion caused the time-domain waveform to look more like a triangle wave (rising and falling during non-negligible periods), you would see more energy in odd harmonics. In general, a signal distorted by an arbitrary, general nonlinear distorting system will spread its energy to many frequencies, including even-harmonic, odd-harmonic, and non-harmonic frequencies. Nimur (talk) 15:35, 14 April 2010 (UTC)

Two answers. First, practically all non-linear loads - the things that induce waveform distortion - do it symmetrically (as a bridge rectifier does), thus all distortion is odd-order. Second, any substantial source of even-order distortion (like a one-way diode shorting the unfuzed line) will cause DC in the line. The grid wasn't designed to feed DC, and numerous client transformers plugged into the grid were not designed to be fed DC... the system goes berserk and then either the culprit disconnects from the grid or it will be tracked quite soon. NVO (talk) 09:23, 15 April 2010 (UTC)

Gravity, friction and mass II

Would you please explain what is conflict in my logic based on my understanding of the laws of physics between statement number 1 and statement number 2. I suspect my knowledge of physics is flawed and I would welcome guidance.

Statement 1.

Two bodies(say a sphere) of identical size and shape are dropped at the same time from the same height. One sphere is filled with lead and the other sphere is filled with feathers. Both spheres will hit the ground at the same time.

Statement 2.

The same two spheres are each placed on identical skateboards and set off at the same time down an identical slope. The sphere filled with lead will pass the sphere filled with feathers.

If gravity is a constant accelerating force what is the explanation for the outcome of statement number 2 ?

Thank you.

86.12.198.101 (talk) 08:42, 14 April 2010 (UTC)

You seem to have asked the samed question here yesterday, and you got several very detailed responses (see Wikipedia:Reference desk/Science#Gravity, friction_and_mass. above). Do you have a follow-up question ? Gandalf61 (talk) 08:54, 14 April 2010 (UTC)

To summarise briefly (just in case you missed the answer in the detail of the discussion), resistances will have an effect, but even if you ignore all resistance, skateboard wheels carry energy proportional to the square of speed, and this energy comes from gravity through the loss in height. A lighter sphere will have less energy to lose, so a bigger proportion will go to the wheels and less will be available for linear speed.

If the spheres were sliding down a frictionless slope with no air resistance, then they would slide at the same speed. Dbfirs 19:27, 14 April 2010 (UTC)

Memory

Today, I realized that it is easier for me to remember the name of a person if I say it out loud at least once with focused attention, rather than simply writing it down and forgetting about it. Is there something to this in the recall process, or is it simply an idiosyncrasy? Why would I be able to better recall a name spoken out loud rather than recalling a note with the name written on it? Viriditas (talk) 09:31, 14 April 2010 (UTC)

I don't know of a name for what you're describing, but I'd say it's not an idiosyncrasy. It's a common suggestion that if you want to remember the names of the people you meet, you want to address them by their names in your conversations with them. Apparently saying their names aloud helps you remember their names. A related phenomenon I've observed is that if you don't know how to pronounce a word or name, it's very difficult to remember it. So vocalizing a word seems to play a role in helping you recall it. --98.114.98.221 (talk) 11:21, 14 April 2010 (UTC)

This is often called Salience (neuroscience) --Digrpat (talk) 14:46, 14 April 2010 (UTC)

Salience, yes, thank you. That was the word I was looking for. Viriditas (talk) 20:36, 14 April 2010 (UTC)

It might be that vocalizing the name develops procedural memory of the name, as opposed to declarative memory. Paul (Stansifer) 17:55, 14 April 2010 (UTC)

Interesting. But, isn't learning a name and saying it more of a declarative memory task? And isn't writing down a name, regardless of the information, a procedural task? I don't think about much when I'm writing, I just do it. Viriditas (talk) 20:36, 14 April 2010 (UTC)

about science

how to study science more easily?  (Unsigned comment added by Sharook (talk • contribs) 15:36, 14 April 2010 (UTC))

It usually helps to have a solid grasp of basic mathematics; depending on how quantitative your scienctific inquiries are, math generally helps. Are you looking for references to books or websites, or do you want some practical study tips? Nimur (talk) 15:38, 14 April 2010 (UTC)

It is "easier" with a gifted instructor who cares whether you learn, and with a good textbook. It is "easier" to become skilled at the math portion of science if you do lots of well chosen problem sets, and that process seems to work best in a group setting, where each contributes. It is also "easier" though not easy, if the learning is as experiential as possible, with good labs and demonstrations. In "bad" labs the emphasis is all on achieving results which are "correct" with a degree of precision greater than the equipment and time provided readily allows, leading to a temptation to "drylab" or fudge results. Edison (talk) 16:11, 14 April 2010 (UTC)

I think it helps if you understand WHY some technique or formula is important rather than learning it 'cold'. It also helps immensely if you choose to learn just because you love the subject. I don't know how old you are - but I was really turned on to science through The Feynman Lectures on Physics (a set of three text-books) which are intended for kids in their final year or two of high school or their first year or two of college. Feynman was the consummate scientist. If you need inspiration, find any biography of him (there are MANY) and be amazed by how he treated subjects as diverse as how to pick up women in bars, how to eradicate ants from his kitchen and how to travel to Tuva with a scientific viewpoint - and had fun doing it. SteveBaker (talk) 18:11, 14 April 2010 (UTC)

Practicing with more scientific experiments can also make science more interesting. ~AH1^(TCU) 23:30, 14 April 2010 (UTC)

May I respectfully remind everyone that not all science is math-based and one needs no more love of math qua math than love of words qua words for most sciences: both are simply useful tools and in many sciences the math is learned long after the initial flame of interest is kindled. I think the key event is seeing how a scientific explanation of something enhances your understanding of it in a way that makes it seem the best way to make sense of it, and leaving you wanting to know more and more things that way. Mine was started by reading Isaac Asimov's World of Carbon at about 13. alteripse (talk) 02:40, 15 April 2010 (UTC)

The only science is physics! Chemistry is just wet physics. Biology is just hydrocarbon-contaminated chemistry. Sociology is just primate biology. The humanities are just sociology for the imprecise. Nimur (talk) 05:47, 15 April 2010 (UTC)

Ob. XKCD: [3] SteveBaker (talk) 13:31, 15 April 2010 (UTC)

This argument is so sophomoric that it makes me nostalgic for college but I'll play another round for the sake of old times. You have the hierarchy inverted. The true intellectual challenge is to scientifically examine systems of more and more complexity, so those who investigate higher order systems deserve more respect than those who stick to math problems. Even more impressive are those who can apply multiple levels of analysis to high-order problems. For example the scientific investigation of diabetes ranges from math, physics, and electronics, to the psychological and social sciences and part of the challenge is to have the wisdom to decide at what level one might best find a solution. Sort of makes a mathematician seem pretty one-dimensional, and a physicist not much better, doesnt it? alteripse (talk) 01:13, 16 April 2010 (UTC)

I think anyone who confines their interest to any one narrow area of study is pretty one-dimensional, but polymaths seems to be rarer these days. Dbfirs 07:08, 16 April 2010 (UTC)

how does the nitrate reduction test work in microbiology?

I'm really really annoyed at my TAs because they seem to avoid organic chemistry explanations like the plague ... they say they can't help me with explaining why one test gives what colour and by what mechanism. OMG. So ... I was hoping someone here could tell me. Supposedly Zn(0) acts like a catalyst(?), but I'm a bit suspicious of people using this term. I rather suspect the zinc actually gets consumed. John Riemann Soong (talk) 16:25, 14 April 2010 (UTC)

We're talking about the nitrate reductase test? DMacks (talk) 17:32, 14 April 2010 (UTC)

Here's a fuller explanation than we have in the article. The test is to see if bacteria have the capability of respiring using NO₃^- in the absence of oxygen. The bacteria are grown in tubes containing media containing NO₃^-. The test to see if they are capable of such reduction is a specific test for NO₂^-. NO₂^- turns reddish purple in the presence of N, N dimethyl-1-naphthylamine and sulfanilic acid. If the bacteria have reduced NO₃^- to NO₂^-, and no further, the color change will be apparent. But if there is no color change, the bacteria may be incapable of NO₃^- reduction, or they may have reduced NO₃^- to NO₂^-, and then further reduced the NO₂^- to N₂ or other intermediates. So we distinguish between these two possibilities by adding zinc to the colorless media. Under acidic conditions, zinc catalyzes the reduction of NO₃^- to NO₂^-. So if there is NO₃^- present in the colorless media, adding zinc will produce the color change and indicate that the bacteria incubated in that medium were incapable of NO₃^- reduction. If addition of the zinc to the colorless media does not produce a color change, it means that NO₃^- is not present, and that therefore the bacteria incubated in that tube were capable of NO₃^- reduction. - Nunh-huh 00:33, 15 April 2010 (UTC)

Thanks! I kinda knew some of that already. What I am really interested in is the organic chemistry of it and the mechanism by which zinc "catalyses" the reduction. What even supplies the electrons? What gets oxidised in the reaction? Are we using metallic zinc, or the Lewis acid catalyst Zn2+? How many steps and intermediates does the reaction go through? It seemed to me that a sulfonic acid was quite oxidised already. Does the napthylamine become a nitro compound and become an aromatic dye? John Riemann Soong (talk) 00:56, 15 April 2010 (UTC)

OK, I currently suspect the napthylamine becomes an amino-napthoquinone, which shows up as red. Can anyone confirm my suspicion? Thanks. John Riemann Soong (talk) 00:58, 15 April 2010 (UTC)

I dunno about the red part of the test, but I'll make what I think is a reasonable guess about the zinc part.

We've got metallic zinc and acidic aqueous solution, right? Two things spring to mind:

• First, metal + acid → salt + hydrogen, so Zn + 2HX → ZnX₂ + H₂.

• Secondly, dissolving metal reductions, such as the Clemmensen reduction. See also the various uses of zinc/acid for the reduction of nitro compounds.

Have a quick read of nitrate reductase test, nitrate reductase, nitrite reductase, nitrate and nitrite just to check the answer isn't there.

There's plenty of info I found with Google, such as Fluka's Nitrate Reduction Test. The detailed description says the red ppt is Prontosil and that Zn powder catalyses the reduction of nitrate to nitrite. I would've thought there'd be plenty of discussion in textbooks and/or the literature on the mechanisms of such simple reactions as [NO₃]⁻ + Zn → [NO₂]⁻. Try electron transfer for starters, or maybe Anal. Chem. (1986) 58, 1590–1591.

Ben (talk) 11:45, 15 April 2010 (UTC)

Thanks so much! I just wanted to update the article as well as improve my own chemical understanding. I'm familiar with the Clemmensen reduction but in that reduction the product is I believe zinc oxide and the fully-reduced (former) ketone/aldehyde. And Zinc here is really a stochiometric reactant and not a true catalyst, right? So Zn2+ acting like a Lewis acid template? The problem is that I can't really see what happens to the nitro group that "activates" the reaction. John Riemann Soong (talk) 15:47, 16 April 2010 (UTC)

Using earwax to test purity of water

I remember, as a child, being told on a wilderness survival course that you could test the purity of water by putting earwax in it. If the wax floated, the water was contaminated; if it sank, it was safe to drink. We were solemnly told not to clean our ears out in the week before a wilderness trip, and to always have a cotton bud in our survival kit.

Is there any scientific logic behind this? To me it now seems plainly wrong. I can see that certain things - salt, for example - would affect the density of the water. But there must surely be all sorts of bacteria which could contaminate water without affecting its ability to support earwax, never mind the obvious flaw that however pure your water was to begin with, it's now got earwax in! --OpenToppedBus - Talk to the driver 16:41, 14 April 2010 (UTC)

Seems entirely bogus to me. As you say - there are a wide variety of factors that could affect the density of the water (not least, temperature) that wouldn't affect your health - and contaminants at the level of a few parts per million that could kill you that would have an utterly negligable effect on density. There is no way this could work. I suspect this was a variety of snipe hunt to persuade kids not to wash their ears before the trip. SteveBaker (talk) 17:58, 14 April 2010 (UTC)

I agree that it sounds silly. Perhaps the logic behind it has to do with the amount of air dissolved in the water. Water with no air in it would be denser, I believe, perhaps causing the Q-tip to float, and this would indicate a lack of plant life, and also wouldn't support many types of animal life, some of which may be harmful to human health. So that may be where the idea came from. However, drinking water just because earwax floats in it is a really bad idea. Just assume it's unsafe and boil it or decontaminate it via another approved method. StuRat (talk) 18:48, 14 April 2010 (UTC)

wielding

what are the sparks from wielding? are they super heated metal filings? —Preceding unsigned comment added by Jonny12350 (talk • contribs) 17:06, 14 April 2010 (UTC)

Yes, they are little burning pieces of metal. By the way, that's 'welding'. Hope this helps, --The High Fin Sperm Whale 17:56, 14 April 2010 (UTC)

I have "wielded" (as in firearms) and "welded" (as in metals with electric arc). The two processes were very different. Edison (talk) 03:33, 18 April 2010 (UTC)

decarboxylation and reduction of pyruvate

Why do these steps in fermentation not yield ATP? I imagine a dicarbonyl is quite electronically strained given the repulsion between the two carbonyl carbons. Furthermore, the reduction of acetaldehyde into ethanol AFAIK is exothermic. John Riemann Soong (talk) 17:32, 14 April 2010 (UTC)

"This tape will self-destruct in five seconds"

What kinds of technologies exist that can make a message self-destruct after it has been heard? Hemoroid Agastordoff (talk) 18:31, 14 April 2010 (UTC)

If it's on computer, just erasing all copies would do the trick. The usual self-destructing casette tape shown on spy shows appears to start a small fire when the tape completes. This would be easy to do in the tape recorder, by ejecting it into a fireproof compartment containing something like match heads, striking them, and having the plastic cassette case catch fire from that. Making the tape itself self-destruct, without help from the player, would require some fancier engineering, and would also destroy the player and maybe set the house on fire. A more realistic way to blank out the tape quickly might be to subject it to a strong electro-magnet. StuRat (talk) 18:37, 14 April 2010 (UTC)

With computers it actually gets trickier unless you are talking about extremely specialized technology. There are a lot of places in a computer's memory that information can reside, and in theory it wouldn't be too hard to hijack a message-delivering program that was trying to delete itself (deny the program the permissions to delete itself, for example). --Mr.98 (talk) 18:46, 14 April 2010 (UTC)

The ultimate form of this is quantum cryptography, where, in theory, the message is physically destroyed (the quantum state is changed) upon observation. This means that no matter what one might want to do with the original version of the message, it is technically gone. --Mr.98 (talk) 18:46, 14 April 2010 (UTC)

Old fashioned way might be to make the tape of a flammable plastic and tight wrap white phosphorous into the tape five second further down the spool than the message. You would have to wrap it un an inert atmosphere but exposed to air when the tape ran on the P would start burning and set off the tape. Or on an iPod record Captain Beaky and His Band immediately after the message forcing the listener involuntarily to smash the iPod up into small pieces... --BozMo talk 19:07, 14 April 2010 (UTC)

If the listener can be trusted to destroy the tape, it could just end "Please destroy this tape within five seconds". If the listener can't be trusted, then it becomes a Digital Rights Management problem of a sort, and there's no secure way to do it because of the analog hole: that is, the listeners could just be recording the audio with a different tape recorder onto a non-self-destructing tape. In that case BozMo's solution is really the only thing that works, although I would suggest "I'm Sad the Goat Just Died Today" by The Frogs, which is so astonishingly unmusical that the destination recorder might shred the tape in protest. Or, if you're working with video, I once saw a DVD player break down thirty minutes into Max Hell Frog Warrior. Paul (Stansifer) 21:03, 14 April 2010 (UTC)

They actually did that (the first thing) in one episode. Phelps played the tape while on a rooftop and instead of the usual self-destruct notice it ended with "Please dispose of this tape in the usual manner". There was a chimney next to him and he dropped it into that to incinerate it. --Anonymous, 21:55 UTC, April 14, 2010.

I picture it dropping safely into a pile of cold ashes, only to be retrieved by the enemy, thus blowing the whole plan. StuRat (talk) 22:17, 14 April 2010 (UTC)

Fortunately, that didn't happen: we saw the puff of smoke as it was consumed. No doubt the head office, although short of white-phosphorus-equipped tapes, had sufficient resources to locate a building where not only was there a place on the roof to conceal the tape, but also a chimney that led directly to an apparatus where the fire was always burning. I mean, anything else would hardly be credible, would it? --Anon, 04:24 UTC, April 15, 2010.

A message on some edible paper provides an easy way to dispose of it. StuRat (talk) 22:19, 14 April 2010 (UTC)

It would be pretty easy to make a special kind of USB key that would run a display program when inserted into a computer and then destroy itself. Looie496 (talk) 01:28, 15 April 2010 (UTC)

A powerful little permanent magnet glued inside the Craig tape recorder after the playback head and before the tape reached the takeup reel would erase it just after it was played. No puff of smoke required. A degaussing coil could be installed under the takeup reel with AC imposed on it when erasing of the reel is desired. That would require a powerful inverter and be far more failure prone than the magnet option. The recording could be on specially made magnetic tape with a nitrate backing (like old movie film) rather than modern plastic. Then a small ignition source like a piece of resistance wire briefly energized would cause the reel of tape to burst into flame, taking the recorder and anything flammable near it with (do not try this at home). If it were recorded on a shellac disc or a wax cylinder it would be easily smashed, melted or burned. If it were recorded on a steel wire from a wire recorder, current could be passed through the wire heating it above its Curie point, thereby erasing it. Edison (talk) 01:41, 15 April 2010 (UTC)

Listen very carefully. I shall say this only once. Cuddlyable3 (talk) 17:44, 15 April 2010 (UTC)

The problem with most of the above solutions involving destroying the tape after it finished playing have some problems: it only takes effect after the tape completely finished playing. So stopping it half a second before the end and rewinding it makes it usable again. A better solution would be to insert an eraser magnet (like what is used when you record a message) right after the place of the reading head. So the message is being erased while it is playing. --131.188.3.21 (talk) 21:44, 17 April 2010 (UTC)

Your statement is clearly incorrect. Please read posts before responding. A magnet which erased the tape immediately after each segment of it played would not allow playback. Edison (talk) 03:29, 18 April 2010 (UTC)

... but it would erase (continuously) a fraction of a second after playback. It could be implemented just by reversing the positions (and connections) of the record and playback heads in a conventional cassette player. I agree that this is not the "Mission Impossible" style of self-destruct, but it satisfies the general query. It does require modified cassette recorders. Dbfirs 16:10, 18 April 2010 (UTC)

Physics - Safer Car

2004 Ford Crown Victoria - Police Interceptor (16 mpg) does not have Crumple zones.

Does that mean it is safer for me to drive in that?

Weight - 4157 lbs for a Sedan (Dinosaur Car aka Traditional Sedan)

Frontal Driver Rating - 5/5 Frontal Passenger Rating - 5/5 Side Driver Rating - 4/5 Rollover 2 Wheel Drive Rating - 5/5

--

2004 Chevrolet Impala (20 mpg) - I think has Crumple zones.

Frontal Driver Rating - 5/5 Frontal Passenger Rating - 5/5 Side Driver Rating - 4/5 Rollover 2 Wheel Drive Rating - 4/5

Just wondering which car to buy from the Police car Auction.

Weight - 3446 lbs

--

A little more information regarding the Crown Victoria which I don't understand whether is a liability or advantage during a crash:

As one of the few remaining passenger cars with body-on-frame construction (that's why it doesn't have Crumple Zones?), it is rugged, and enables repairs after minor accidents without the need to straighten the chassis – an important benefit for a car frequently used by police forces for PIT maneuvers, a maneuver in which the back left or back right corner of a fleeing vehicle is gently pushed with the front left or front right corner of the chase vehicle, disrupting tire adhesion on the fleeing vehicle with the goal of causing the fleeing vehicle to rotate and decelerate.

--

I would like to have bought the Safest Car on the market right now, which is Lexus 2010 with all the new electronic safety features that take it one step towards driver-less cars. Or the Ford Taurus 2010 which has the most of the new electronic features safety features. But I am not able to afford a brand new car, let alone a "Luxury Car" such as the Lexus.

I don't need all the space afforded by the car. But because on the road there are Pick-up Trucks/SUVs/Sport Utility vehicles it makes it necessary to buy a heavier car. But I don't think buying a Pick up truck is safer, because it is more prone to roll-overs. It will be mostly only 1 person using the car i.e. no passengers or luggage.

I think people who buy very small cars - Smart Cars/Honda Fit for a higher mpg are foolish, as they will suffer severe injuries or even death if they crash with the big vehicles mentioned above (or even for that matter a mid-size vehicle like Corolla).

Since I don't have a blank cheque to pay for Gas like Police departments, I am considering 2004 Chevrolet Impala vs. 2004 Ford Crown Victoria. These are cars that are part of most police fleet, with Crown Victoria having a 80% market share.

The Crown Victoria sedan 16 mpg has a lower mpg than a Dodge Caravan SUV which is 18 mpg.

--33rogers (talk) 19:10, 14 April 2010 (UTC)

Well, in the UK the Lexus's selling point is that they combine luxury car features with family car prices. When I was buying a new car a couple of years ago, it was a little (say 15%) dearer than Toyota or Honda, but lots (say 30%) cheaper than BMW or Audi. So don't write it off. Lexus have been producing cars for some time so why not look for a used model? --TammyMoet (talk) 19:22, 14 April 2010 (UTC)

Read Driver-less_cars#Driver-assistance section, then you will see that all new safety features only the "Luxury Cars" of 2009/2010 have them, with the exception being the Taurus.--33rogers (talk) 19:37, 14 April 2010 (UTC)

Crumple Zones are a safety feature. All else being equal, you want them in your car. Of course, they make the car harder to repair after an accident, but If I have to have unrepairable damage, I'd rather it be to my car's frame and not to my own. APL (talk) 19:25, 14 April 2010 (UTC)

If nothing else changed, a car with crumple zones would be safer, in general. However, the Crown Vic is a larger car, which also gives you more distance, and thus time, to decelerate the passengers during a crash, as well as the more mass working to push smaller cars out of the way in an accident. So, which car is actually safer, I can't say. I suggest looking up the safety stats for each. StuRat (talk) 19:31, 14 April 2010 (UTC)

Just thinking, Would it be easier to maneuver a mid-size car like the Chev Impala, to prevent a crash in the first place? Should that be also a factor to consider in the decision making process? --33rogers (talk) 19:42, 14 April 2010 (UTC)

Yes, all things being equal, a smaller car will have a smaller turning radius, and otherwise be more maneuverable. However, safety features like anti-lock brakes and traction control may have a greater effect than vehicle size. StuRat (talk) 20:19, 14 April 2010 (UTC)

Regarding Crumple Zones, my theory is this: a car with crumple zone will absorb more impact of the forces in a crash? Whereas the other car Crown Vic, which has no crumple zone, will be deflecting most of the crash force impact to the other car, thus being more safer? --33rogers (talk) 19:46, 14 April 2010 (UTC)

No - folding crumple zones transfer the energy into the car - thus, away from the passengers. The car has the distance of the crumple zone in order to slow down...It's like having a few feet of brakes before the collision. Vimescarrot (talk) 19:52, 14 April 2010 (UTC)

Agreed. StuRat (talk) 20:19, 14 April 2010 (UTC)

Rogers, the physics don't work that way. You really don't want a rigid collision. Any sort of "deflection" would result in the car suddenly going one way and passengers going a different way. You want to ease into those direction changes, and crumpling is a way to do that. APL (talk) 05:05, 15 April 2010 (UTC)

Note also that cars are not solely designed to maximise the safety of the occupants; they are also designed to minimise, as far as practicable, damage/injuries to what the car hits, especially pedestrians. Crumple zones to some extent (though body shape to a larger one) can reduce an impact sufficiently to, sometimes, reduce the effect of a collision to injury from what otherwise might have been death. 87.81.230.195 (talk) 12:15, 15 April 2010 (UTC)

I don't see any of these answers noting that the police car must be able to purposely collide with another vehicle without crumpling. For example, you must be able to do a PIT maneuver without the front of the car collapsing into your front wheel. Therefore, crumple zones are removed. -- kainaw™ 13:19, 15 April 2010 (UTC)

The part of a car that is responsible for the most accidents is the nut behind the wheel. Cuddlyable3 (talk) 17:47, 15 April 2010 (UTC)

Ah yes, there's also a nut loose on my keyboard that sometimes causes similar problems. :-) StuRat (talk) 02:21, 17 April 2010 (UTC)

Flashing of white tail by alarmed animals

I disturbed a Muntjac deer by the side of the road, and as it ran away it raised its short tail showing a very visible white 'signal', just as a rabbit would. When it stopped with a lowered tail it almost disapeared as the colour of its fur matched that of the floor of the wood, and if I had not seen it moving earlier I would never have noticed it.

What is the evolutionary purpose of the white tail signal? It would make it much easier for a predator (or hunter) to see it and follow it, so more likely to be eaten. How could it have evolved? I'm not sure it would even help the relatives of the alarmed animal (and hence pass on those genes even if the target animal was killed) as its running away ought to be enough to tell them to be alert. 78.149.114.89 (talk) 19:44, 14 April 2010 (UTC)

May be there was a young fawn near by that you did not notice because you had your attention atracted to the white tail? 169.139.217.79 (talk) 19:49, 14 April 2010 (UTC)

I think the idea is this:

1) The predator starts to chase they prey.

2) The prey, knowing it has been spotted, raises the tail, as there's no point in hiding now.

3) The predator fixates on the easy to see tail during the chase.

4) The prey then lowers the tail, while changing direction, stopping or otherwise hiding it's position.

5) Had the predator been tracking some other part of the prey, it might have kept it in sight, but, having tracked the tail, which is no longer visible, it loses sight of the prey animal long enough for it to escape.

From the deer's behavior, it sounds like you got the standard anti-predator treatment, which seemed to work properly. As far as the deer is concerned, it just saved itself from being eaten by you. StuRat (talk) 19:55, 14 April 2010 (UTC)

This is common in many animals - not the 'broken wing' behavior certain birds use to draw predators away from their nests. the evolutionary advantage is that a predator has a much lower chance of catching an animal that is alert to its presence, so any animal that is aware of the predator and can attract its attention lowers the risks to nearby (unaware) prey animals at minimal risk to itself. --Ludwigs2 20:17, 14 April 2010 (UTC)

I'm not sure I would have seen it running away without its raised tail, so that knocks out the logical sequences suggested above. 78.149.114.89 (talk) 22:30, 14 April 2010 (UTC)

Not really, that just means you aren't as good of a predator (at least as far as eyesight goes) as the deer thought you were. StuRat (talk) 00:32, 15 April 2010 (UTC)

Mainly because he was not a predator (he wasn't hunting was he?), but the deer didn't know that. 169.139.217.77 (talk) 01:20, 15 April 2010 (UTC)

I'd swear I saw a documentary that referred to the deer's tail, and similar markings in other species, as "follow-me" markings. They said that the purpose was to keep the herd moving together—to alert the other deer, and make it easier for them to follow the leader. I am unable to find a reference for this explanation at this time. -- Coneslayer (talk) 12:31, 15 April 2010 (UTC)

They might well use it for other purposes like that, but, in this case, intentionally raising the tail when it thinks it's been spotted by a predator shows it's using the tail to help it escape. StuRat (talk) 14:42, 15 April 2010 (UTC)

A deer is not clever enough to do the reasoning you have described. Its just an instinct. See anthropomorphism and anthropomorphic fallacy. Although I'm not sure that either of those terms is the correct one to mean giving animals the same thoughts and feelings as humans, like Walt Disney. 78.151.110.54 (talk) 14:18, 16 April 2010 (UTC)

It's painful to write about animal behavior in a way that doesn't use words we normally apply to humans. We just don't have words to describe it. Instead of "it thinks" we should say "impulses travel from neuron to neuron in it's brain, recognizing the pattern of predator pursuit and causing a predetermined instinctual set of signals to be sent to the appropriate muscles in it's tail" ? If you wish, please rewrite my entire 5 steps that way. I have better things to do. StuRat (talk) 02:14, 17 April 2010 (UTC)

No need, Stu. Your statements were accurate except perhaps that "instinctively" should replace "intentionally". The anthropomorphism was in the mind of the reader. Dbfirs 19:13, 18 April 2010 (UTC)

Cryptorchidism in patients with 5-Alpha-Reductase Deficiency. [?]

I have several questions concerning people with 5-Alpha-Reductase Deficiency. The wikipedia article says that (in childhood) they are often raised as girls because their external genitals are indistinguishable from those of natal females. At puberty, however, they are identified as boys due to —among other sex characteristics— their clitorises growing into (very small) penises and their testes descending.

My first question deals with the location of said testes in a post-pubertal man with 5aRD: How far below his abdomen are said testes located (vis-á-vis a typical, adult man)? I've tried finding images of people with 5aRD —both men and children— but thus far have come up fruitless.

Also, are patients with 5aRD more likely to develop testicular torsion, cancer, and other maladies as a result of this condition? Or is there some other factor that I'm failing to take into consideration?

May these individuals be benefitting from the action of superficial veins (notably, the Great Sapphenous Vein) providing blood to their testes cooler than arterial or deep-vein blood? Has anybody looked into this? Where may one find articles and pictures of this fascinating condition? Pine (talk) 20:48, 14 April 2010 (UTC)

I moved this question to Talk:5-alpha-reductase deficiency. Check there for the answer. alteripse (talk) 02:08, 15 April 2010 (UTC)

Cat and dog repeller

Does anyone know of any way to repel cats and dogs (and even deer) from moving vehicles on a 50 kilometres per hour (31 mph) or less road? I've seen so many cats, dogs, and deer hit on this road, I'm wondering if there's something I can affix to my car to give the little critters a fighting chance. Thanks. Viriditas (talk) 20:58, 14 April 2010 (UTC)

Do you mean to lessen the blow if you hit them, or to make it less likely they'll get hit at all? If it's the second i'm not sure there's much you could do yourself, but protective fencing would help, also more 'openess' would probably help too - I find that mostly it's animals coming out of bushes and straight onto the road is a common cause (though Pheasants do seem to be constantly suicidal no matter what you do to try stop it). ny156uk (talk) 21:53, 14 April 2010 (UTC)

Yes, I often run down peasants pheasants. StuRat (talk) 22:00, 14 April 2010 (UTC)

Those big spotlights on the roof, like on a redneck's truck, would probably give them more warning at night. However, you might cause traffic accidents and they might be illegal. StuRat (talk) 21:58, 14 April 2010 (UTC)

You could also make more noise, say by keeping the windows down and radio on. But, again, this would annoy the neighbors. Perhaps a sound that only cats and dogs could hear would be in order. StuRat (talk) 22:02, 14 April 2010 (UTC)

They make lots of products similar to these specifically for deer. I've heard some town councils in areas with deer/car problems encourage people to install them. Beach drifter (talk) 23:03, 14 April 2010 (UTC)

a little explanation Beach drifter (talk) 23:04, 14 April 2010 (UTC)

(Edit Conflict) In my experience (with deer, badgers, etc. in the New Forest, other Hampshire and Southern English locales, and in Scotland), the best way to minimize/avoid impacts is to drive slowly and very carefully, keep a constant lookout, and slow down or stop whenever necessary. Animals tend not to understand, or rapidly get accustomed to, traffic noises both usual and unusual, and extra noise-making mechanisms would be extremely irksome for local human inhabitants, should there be any in earshot. Deer in particular are apt to be dazzled by lights and and freeze (hence the illegal hunting method of lamping), and also react unpredictably to traffic, sometimes leaping into a vehicle's path at the last second; cats are also prone to this. Of course, driver caution is enhanced in the New Forest because within its boundaries all animals (including the numerous free-roaming ponies and cattle) have automatic right of way and it is a fineable offense to hit one whatever the circumstances.

Within ten miles of my own house, in the Forest of Bere, I have had at times to slow down or stop for mice, weasels, partridges, owls (who like sitting on the median line), rabbits, (domestic) cats, fox cubs (adults tend to get out of the way) badgers, deer, and what appeared to be a juvenile puma (duly reported to the Big Cats in Britain Society - what, no Wiki article?). 87.81.230.195 (talk) 23:08, 14 April 2010 (UTC)

Just as a side comment: a few years ago I drove on U.S. Route 191 in southeastern Utah at dusk. A national park ranger had described the route as "Deer Alley", and so it was. The road was festooned with signs and they were fully justified by the number of deer nearby. I was particularly taken by the signs that said WATCH FOR DEER IN YOUR LANE — deer in someone else's lane obviously being someone else's problem! --Anonymous, 04:27 UTC, April 15, 2010.

I'm sure the deer will signal before changing lanes. :-) StuRat (talk) 14:35, 15 April 2010 (UTC)

Bear locomotion

While bears run... how do they land with their feet? heel first or toes/front part first? --Belchman (talk) 21:47, 14 April 2010 (UTC)

I watched some bear movie clips on YouTube - it looks to me like their claws/toes hit the ground before the heel. But there are a lot of species of bear out there. Anyway - you can watch bear videos just as easily as I can...so tag! You're it! SteveBaker (talk) 04:06, 15 April 2010 (UTC)

Mastering crystallography

Within a week, I need to master crystallography, with emphasis on X-ray crystallography, because my 4th year biochem final exam will be heavily based on crystallography. The exam will test concepts as well as applications like doing some simple calculations involving space groups, coordinates, etc. Will it be possible to master the topic within that time frame? My plan is to read the book "X-ray crystallography made crystal clear" twice while taking notes. But I found that some pages are hard to understand due to heavy mathematics. For someone like me with only Calculus 1 and 2 background to fully understand crystallography, what other better, more easily-accessible resources or webpages are there to help you master crystallography? Thanks. —Preceding unsigned comment added by 142.58.132.157 (talk) 21:55, 14 April 2010 (UTC)

See Main Page - Online Dictionary of Crystallography. -- Wavelength (talk) 23:09, 14 April 2010 (UTC)

Wikipedia has articles on X-ray crystallography and Crystallography. Cuddlyable3 (talk) 17:15, 15 April 2010 (UTC)

doctors dont wear gloves

why dont doctors dont wear gloves? example http://www.youtube.com/watch?v=NMxqzZW2Z8c&feature=channel

they never do —Preceding unsigned comment added by Jonny12350 (talk • contribs) 22:32, 14 April 2010 (UTC)

The naive thought is that bare hands are always dirty and gloved hands are always sterile. But it's not always like that. Obviously a gloved hand can be dirty if it has touched something dirty. Similarly, hands can stay relatively sterile if they are washed properly and don't come into contact with anything after cleaning. An ungloved hand also can better feel nuances that a gloved hand could miss, which might be important for certain types of examination. OK maybe not for proctology exams.

Gloves also have another purpose, to protect doctors from contagions. However, a gloved hand can still be rubbed in the eyes, spreading disease to the doctor, just like bare hands. So it may come down to the only advantage of gloves being that they serve to remind the doctor not to touch his hands to anything he shouldn't. Instead, maybe a few shock treatments would make that lesson permanent. :-) StuRat (talk) 23:02, 14 April 2010 (UTC)

Wearing gloves is in most cases offers only a source of false security for the real purpose intended because they are not replaced at the appropriate time. Have you not seen restaurant workers continue to wear their gloves to protect their hands from soil when dumping trash or even cleaning the rest room? Washing hands is therefore the preferred method since one will do it more likely than replacing gloves to keep their own hands clean. 71.100.8.49 (talk) 22:53, 14 April 2010 (UTC)

Further, doctors always wash their hands upon entering any room, and after touching just about anything. Beach drifter (talk) 22:57, 14 April 2010 (UTC)

I have a disgusting story about rubber gloves. There was a janitor at a hospital who was apparently mentally retarded. They made him wear gloves when tossing out the garbage, some of which was medical waste. He then went to the cafeteria, with his gloves still on, and handled all the food at the salad bar, such as eggs, looking for "just the right one". In his mind, since he was wearing gloves, his hands were clean, so it was OK to touch the food. He was reprimanded. StuRat (talk) 00:29, 15 April 2010 (UTC)

The premise is false. Doctors always wear gloves when there is a requirement for sterility. Looie496 (talk) 01:23, 15 April 2010 (UTC)

First up, wearing gloves does not provide sterility unless the gloves are sterilised. The huge majority are not. Asking why doctors don't wear gloves is like asking why policemen don't smile. The truth is some of them do and some don't. It depends on a wide variety of circumstances and a wide variety of attitudes. There is a widespread belief within the UK National Health Service that doctors are among the worst observers of hygiene and prevention of cross-infection procedures. Never mind the hands, watch out for the tie! Richard Avery (talk) 07:31, 15 April 2010 (UTC)

hi OP here. all of you are answering about sterility that was never my question. im talking about protecting the doctors from contagions. like hepatitis c ect. if hes not wearing gloves when contacting blood wont he catch it ? —Preceding unsigned comment added by Jonny12350 (talk • contribs) 10:14, 15 April 2010 (UTC)

He's not contacting blood (except with the end of the needle, which he'll not subsequently touch directly), he's only contacting skin which he's already sterilised (though primarily to avoid pushing skin bacteria in with the needle). Few contagions are easily (if at all) passed on by casual unlesioned skin-to-skin contact. 87.81.230.195 (talk) 12:05, 15 April 2010 (UTC)

NOT TRUE WHEN HE PUTs a swab on the site afterwards he touches blood iv even had minor surgical things done on me where the doctor got plenty of blood on him and didnt wear gloves sry caps —Preceding unsigned comment added by Jonny12350 (talk • contribs) 13:34, 15 April 2010 (UTC)

There aren't many diseases you can catch merely by getting someone's blood on your hands (an exception would be if you had a cut or hangnail). In general, you must then touch your hands to a mucous membrane, such as the eyes, for the contagion to gain entry into your body. However, you can do this whether you have gloves on or not. After contacting potentially contagious blood, the hands should then be sterilized, or the gloves removed. There is a problem with removing gloves, though, that it's easy to spread the blood from them onto something else while doing so. So, while the gloves do provide some protection in the case of minor cuts on the hands, they also have this drawback. StuRat (talk) 14:32, 15 April 2010 (UTC)

It is likely the medical/sanitary equivalent of security theater, that is it isn't a marked increase in sanitation when you wear the gloves; but the gloves make the customer/patient/even the doctor feel better about their own sanitation. Washing properly, and avoiding contacting problem areas afterwards, is likely the best method; but as a customer/patient, you don't see the washing go on, so you have no evidence that it happened. You can see the gloves, so you can get a better sense of security in seeing them, even if they are no actual proof of them improving sanitation in any way. --Jayron32 15:02, 15 April 2010 (UTC)

yes but if you have an even tiny micro tear on your hand (there seem to be alot near the fingernails) couldent he get infected with hep c  ? —Preceding unsigned comment added by Jonny12350 (talk • contribs) 18:30, 15 April 2010 (UTC)

Possible, but unlikely. The reduction in the ability to feel through the gloves could also make other accidentally exposure, like the doctor cutting himself with a scalpel, more likely. StuRat (talk) 18:34, 15 April 2010 (UTC)

Fractals and the structure of the brain

Is there an article or reference for any coverage or discussion of fractal based structure of the brain. As I recall by using certain chemical procedures to process the tissues of the brain a network structure is revealed that mimics either fractal analysis of blood flow through healthy or through cancerous tissue. 71.100.8.49 (talk) 22:48, 14 April 2010 (UTC)

A Google Scholar search for "fractal structure of the brain" finds a number of things, including PMID 14642486 and PMID 16112737. Looie496 (talk) 01:21, 15 April 2010 (UTC)

Birds riding thermals

Why is it that some bird species can use thermals to go really high up into the sky whilst other birds appear to be completely unable? I've seen hawks and gulls riding thermals but I don't think that I've ever seen something like a pigeon, or a duck, or a starling doing the same. —Preceding unsigned comment added by 95.148.104.4 (talk) 22:52, 14 April 2010 (UTC)

Birds like hawks, vultures, pelicans, and so on have much larger wings to take advantage of rising air current, and also have a need to be spending time high in the sky, that is how they find food. A pigeon has neither the wing area nor the desire or need to soar. Beach drifter (talk) 22:59, 14 April 2010 (UTC)

Also, large birds can't fly by flapping alone, that uses too much energy when you're that big. StuRat (talk) 23:04, 14 April 2010 (UTC)

The peregrine falcon, a large bird, can use thermals to get to high altitudes then dive down by taking advantage of their weight and gravity at extremely high speeds to catch prey. ~AH1^(TCU) 23:26, 14 April 2010 (UTC)

A couple of years ago I saw a flock of geese rising on a thermal. I've only seen it the one time, and it must have been a hell of a thermal, because geese normally have to work pretty hard just to stay in the air. Looie496 (talk) 01:17, 15 April 2010 (UTC)

Birds are evolved to do what they need to do to survive in whatever environment they inhabit...look at an albatross File:Albatross shape.png and compare to a sailplane File:Dg800.jpg - both are designed to glide, take advantage of thermals - and guess what? They both have long, skinny wings. Compare a hummingbird File:Archilochus-alexandri-002-edit.jpg to a helicopter File:Indian air force dhruv helicopter j4042 arp.jpg - the wings are about half the length of the body in both cases. A Perigrine Falcon folds its' wings back for speed in a dive File:PeregrineFalconSilhouettes.svg - not unlike a swing-wing Panavia Tornado File:TornadoGR1 27Sqn RAF Mildenhall 1988.jpeg that retracts its wings for high speed flight. The point being that you don't build a jet fighter with long spindly wings - and falcons didn't evolve long spindly wings either. They simply aren't evolved to glide - they don't need to...and albatrosses don't need speed. SteveBaker (talk) 03:53, 15 April 2010 (UTC)

See wing loading. Hawks, eagles and such have low wing loading and can soar, but don't go very fast (peregrine falcons aside, who close their wings when they stoop from a height). Ducks, on the other hand, fly very fast and efficiently due to their smaller, low-drag, highly-loaded wings. The penalty is that they descend rapidly when they stop flapping - watch a duck land alight and see how steeply they descend. An efficient glide ratio is necessary for soaring, as the rising air must exceed the bird's descent rate. Acroterion _(talk) 17:07, 15 April 2010 (UTC)

How do gulls manage both soaring and fast, flapping flight, as a matter of interest? I read somewhere the other week that a Herring Gull can pull 40mph+ in still air (say, if pursuing a duck or a puffin with intent to kill/steal food) and probably a lot more with the wind behind it - yet the HG can also soar for hours, seemingly effortlessly on thermals and ridge lift, keeping an eye out for food. They seem to have the best of both worlds - but why? --Kurt Shaped Box (talk) 17:38, 15 April 2010 (UTC)

They're just at the transition in size where they can do a bit of both, but probably not either as well as a hummingbird hovers (by flapping) or a albatross hovers (by soaring on thermals). StuRat (talk) 18:50, 15 April 2010 (UTC)

Gulls do seem to be wonderfully 'mid-range', general-purpose creatures, in terms of their adaptations and abilities - they don't exactly excel at any one thing but they can fly, glide, swim, run, hunt and scavenge with reasonable aptitude, eat a huge range of foodstuffs - both animal and vegetable, they can generally defend themselves against any predator fast enough to catch them and generally move too fast for any predator strong enough to overpower them. They're also quite intelligent and resourceful, as it goes - and they live a long time, with a fairly consistent reproductive rate. I think that this is probably one of the winning formulas, in terms of the success of a species. --Kurt Shaped Box (talk) 20:47, 15 April 2010 (UTC)

Reading all that, one might actually get the impression that you like gulls. :-) StuRat (talk) 19:31, 16 April 2010 (UTC)

One other advantage to gulls, they are able to live either with, or without, people. Not all species can. StuRat (talk) 19:42, 16 April 2010 (UTC)

I do admire the gulls for their toughness and adaptability, FWIW - but mainly, I just think that they look cool and have a lot of character. I think that the key to survival on the Planet of The Humans is probably not to be too fussy about food or habitat - and to always maintain a healthy mistrust of people, albeit not to the extent of constant fear (which could get in the way of feeding opportunities), whilst having little-to-no economic value as meat/skin/other biological products or as a pet. --Kurt Shaped Box (talk) 21:33, 16 April 2010 (UTC)

Note that there are also several other methods of gaining lift similar to "riding on thermals". In one, instead of vertically rising columns of heated air, there is a horizontally moving "river of air". This can happen in a mountain pass, for example. The birds use this fast moving air to gain speed, then trade this horizontal speed for altitude, once they leave it. Once at altitude they do their scanning for prey. When they lose enough height, they go back into the "river of air" for another boost. StuRat (talk) 18:57, 15 April 2010 (UTC)

Birds riding the jet stream ?

Can any birds do this, or is it just too fast, too high, and too cold for them ? StuRat (talk) 18:59, 15 April 2010 (UTC)

Andean condors are occassionally seen at extreme altitudes of about 30,000 ft which might brush the lower end of the jet stream, but they are not at the same latitude as the jet stream. Even if they could use it, would they want to? They would have a really hard time getting back to their previous location. Googlemeister (talk) 20:29, 15 April 2010 (UTC)

If the jet stream is headed in the direction they wish to migrate, it seems like it would save them a lot of time and energy, if they could ride it. StuRat (talk) 18:33, 16 April 2010 (UTC)

I believe that I've read about birds (unsure of the species) flying above the summit of Mt. Everest - which, IIRC pokes up into the jet stream. --Kurt Shaped Box (talk) 20:47, 15 April 2010 (UTC)

Tropical birds have been known to ride in the eye of a tropical cyclone, as that was the only spot with calm winds where they could survive, only to end up thousands of kilometres from their starting point when the storm makes landfall over a non-tropical region. ~AH1^(TCU) 16:25, 17 April 2010 (UTC)

April 15

Caustic size variation with temperature

I've noticed that you can see how cold a swimming pool is when it is lit by sun and the water is not still by simply noting the pattern of light dappling the bottom. Cold water has smaller sharper looking caustic patterns while warm water has large soft and slowly moving caustic patterns. Why? -Craig Pemberton 02:09, 15 April 2010 (UTC)

It may not be the overall temp that's directly important, but rather the range of temperature variations within the pool, as each temperature change has an associated change in density, and thus a refraction occurs at the boundary layer. Perhaps a pool which is overall colder but also in sunlight tends to have more temperature variations, and thus more refraction ? StuRat (talk) 02:14, 15 April 2010 (UTC)

ISS EVA Capabilities

Hey everyone and thanks in advance for reviewing my question. The bottom line of my question is: does the staff stationed at the International Space Station have the ability to do EVAs (spacewalks) when there is no visiting mission (NASA Space Shuttle or otherwise). In response to the current valve failure in the nitrogen/ammonia tank assemblies, a lot of talk is heard about whether an EVA could be done during this shuttle mission or the next, however I hear no talk about whether the station crew could do a spacewalk during the interim. Obviously, it would be preferable to do spacewalks during visiting Shuttle missions, because the astronauts going up have the ability to train for the exact procedure in advance, but in a more urgent situation, is it possible (with standard equipment kept on the Station, etc.) for the station crew to do a spacewalk during a time when there is no docked mission vehicle? --Nick—^Contact/_Contribs 04:25, 15 April 2010 (UTC)

Sure, They've got both the Quest Joint Airlock and the Pirs docking compartment, though the later is apparently only compatible with Russian suits.

This has been done a number of times. Check out the List of spacewalks since 2000. I believe that all the space walks where "Expedition [number]" is listed as the "Space craft" were based from the space station when no shuttle was docked. (This list is not terribly clear on this point.) APL (talk) 05:15, 15 April 2010 (UTC)

I notice the quest airlock says it allows both kinds of suits, however the Pirs only allows the russian Orlan suits. What is the factor that prevents a US suit being used in the Pirs airlock? Some sort of coupling? I didn't think you had to be coupled during EVA. Vespine (talk) 06:02, 15 April 2010 (UTC)

I'm guessing - but I know that you have to pre-breathe pure oxygen for quite a while before you go outside in order to purge nitrogen from your system to avoid getting "the bends" in the lower pressures used in the spacesuit. That takes a long time - and it has to be done in the airlock because the pressures have to be gradually reduced while you do it. You wouldn't want to be using your limited supply of suit oxygen for that - so if the issue is one of suit couplings, that would explain the problem. SteveBaker (talk) 13:26, 15 April 2010 (UTC)

Car trick

I was looking at the following video: http://www.youtube.com/watch?v=qKxgNOR5QnY&feature=related, and I had some questions about the physics. First, how stable is the car in this situation? It seems precariously close to falling over, but often looks can be decieving. I would imagine that, for the trick to have any reasonable chance of success, the car has to be somewhat stable. But from what I can see, the center of mass seems to be nearly over the the wheel. Do you think weights were added to the left side of the car to make it appear less stable than it actually is?

Second, would it be possible to use the gas in this situation, what with the wheel not being flat on the ground? Thanks 173.179.59.66 (talk) 09:34, 15 April 2010 (UTC)

Oh, and how do you think they would return the car back to its original position? I would think a sharp right turn would do the trick, but is turning right really and option when only two wheels are on the ground? 173.179.59.66 (talk) 09:36, 15 April 2010 (UTC)

Here's the Wikipedia article on it Ski (driving stunt). 194.221.133.226 (talk) 10:03, 15 April 2010 (UTC)

though i'm not convinced by the article - my understanding was that you needed specialist work done to the Axles as otherwise they basically just snapped...That said maybe what I head was a load of cr@p. 194.221.133.226 (talk) 10:05, 15 April 2010 (UTC)

A lot depends on the weight of the vehicle. Something as heavy as the vehicle in the video might well need stronger axles - but I've seen the stunt done with lightweight vehicles that have definitely not been modified ([4], [5], [6], [7], etc). The difficulty lies in getting the vehicle in that position in the first place - you have to hit the ramp at a fairly exact speed to get it to that position without tipping over. However, once it's up there (I'm told), keeping it there is relatively easy - and the larger the vehicle, the easier that is. This is one of the more easily done car stunts - you just have to practice the "getting it up to that position without rolling it over" part. The moment of inertia of a car is huge - it responds fairly sluggishly and you have plenty of time to react to keep it up on two wheels. Steering is done much like on a bicycle...and again, I'm told that isn't difficult. SteveBaker (talk) 13:21, 15 April 2010 (UTC)

as in you haven't ridden a bycycle SteveBaker or as in the steering isn't difficult (much like riding a bike isn't). 194.221.133.226 (talk) 14:47, 15 April 2010 (UTC)

Russ Swift is a well-known stunt driver who regularly appears on Top Gear episodes doing stunts such as these (amongst many others). He also showed Jeremy Clarkson how to do the ski in one of Clarkson's motoring specials. Zunaid 14:55, 15 April 2010 (UTC)

The car in that trick is about as stable as a bicycle. In both cases keeping balance is by a combination of leaning one's body and steering. Having power steering may help. It looks like the stuntmen are not too stressed to wave to the onlookers. I don't think any weights were added to the car. Higher air pressure in the tires might help. The car in the video is probably not the first one in which the driver has tried the trick because it looks undamaged. It is unsurprising to see the trick done by arabs with enough disposable income to play with new vehicles, insignificant fuel price and wide open flat roads without much traffic regulation. Ancestral skill at balancing on lurching camels may help too.
@Second, yes the driver uses the engine to keep the car moving because otherwise it would slow to a stop and become harder to keep balanced when one loses the gyroscopic effect of the rotating wheels. Like on a bicycle. I think the car drivetrain needs to have an LSD or 4WD to sustain the trick.
@Last I'm sure it is easier to come down with a bump than it is to go up. Getting up seems extra risky when done without a ramp but I never saw an example of a car overtoppling on youtube. Cuddlyable3 (talk) 16:47, 15 April 2010 (UTC)

One of the finest articles on Wikipedia is Bicycle and motorcycle dynamics - it says that the idea that some gyroscopic effect is responsible for the stability of a bicycle is discredited. It's all to do with the angle of the front forks. However, the geometry of the steering mechanism of most cars confers similar stability in this case. SteveBaker (talk) 23:29, 15 April 2010 (UTC)

Thanks for the quick replies! Quick question about the stability though. On a bike I'm abe to stay upright by shifting my weight. If the car were to start falling one way or another, how could the driver compensate?173.179.59.66 (talk) 05:22, 16 April 2010 (UTC)

By turning the wheel left/right which will move the car in the (hopefully) opposite direction in which it is falling. Ariel. (talk) 12:48, 16 April 2010 (UTC)

The driver will shift his body weight too. I don't think anyone does the trick while wearing a seat belt. Cuddlyable3 (talk) 23:13, 16 April 2010 (UTC)

Wolverine vs Honey Badger

In a hypothetical fight to the finish, which one would most likely be left standing? Exxolon (talk) 10:02, 15 April 2010 (UTC)

Quite clearly the wolverine. The wolverine often takes prey such as reindeer calves. While both are omnivores, the wolverine can grow heavier than 20-23kgs, whereas a honey badger will not become much more than 14kg (this according to their respective articles). Badgers in general will far more often dine on animals lesser in size than themselves. 88.90.16.251 (talk) 12:20, 15 April 2010 (UTC)

Are you sure? I've seen a video of a honey badger seeing off a lion. Zzubnik (talk) —Preceding undated comment added 13:30, 15 April 2010 (UTC).

Lions tend to be non-confrontional, and regularly back down from fights with smaller animals. Hyena are often observed chasing lions off. Lions would win if they fought such an animal, but they tend to not want to. --Jayron32 14:58, 15 April 2010 (UTC)

Well, not to be overly pedantic or anything, but if the lion backs off, the lion loses the fight, right? He's disqualified himself out of sheer cowardice. Comet Tuttle (talk) 18:17, 15 April 2010 (UTC)

I think if the lion and the honey badger were locked in a cage, and had to fight to the death, the lion could tear it to shreds. If forced to fight, the lion wins. If it doesn't have to fight, however, why bother? --Jayron32 18:54, 15 April 2010 (UTC)

Predatory animals don't generally like to engage in fights against opponents where there is a non-insignificant chance of injury. Injuries, even small ones, tend to add up over the years, you see - and affect the predator's ability to hunt. Impaired hunting ability = death in the cold, hard, brutal indifference of nature. So they will only tend to go after what they consider to be 'soft targets' - unless the situation is extremely dire. --Kurt Shaped Box (talk) 20:59, 15 April 2010 (UTC)

Indeed in such circumstances both win. The larger animal who could have won the fight but would have suffered unnecessary injury doesn't suffer that injury and the smaller animal who would have lost the fight lives another day. One might argue similar things for most human fights where generally the outcome for both is better if they just don't fight. It's usually unfair to say the person who backed down 'lost' just because they avoided a silly fight which would have benefited no one. Nil Einne (talk) 07:42, 16 April 2010 (UTC)

now result

i am very angry to use this web page but could not have any result pattaining to my search —Preceding unsigned comment added by 41.202.199.4 (talk) 11:36, 15 April 2010 (UTC)

If you can let us know what you were searching for, we might be able to help you find it. Karenjc 12:22, 15 April 2010 (UTC)

A little atitude adjustment is likely in order as well. Dauto (talk) 14:19, 15 April 2010 (UTC)

I was assuming that, since the OP's first language doesn't seem to be English and his IP address geolocates to Cameroon, what he meant could have been closer to "I feel bad about coming here asking, but I can't find what I need by searching". Karenjc 14:36, 15 April 2010 (UTC)

Also a little spelling adjustment?--79.76.228.211 (talk) 14:59, 15 April 2010 (UTC)

Could you be looking for something called "NOW", such as the National Organization for Women ? StuRat (talk) 14:21, 15 April 2010 (UTC)

What do these symptoms lead to?

I have been given a fake "patient" with the following symptoms: fever, dizziness, vomiting and diarrhea, a diffuse maculopapular rash on all limbs, puffy edema of the face and extremities, and raised temperature, pulse, blood pressure, and respiration. What do these symptoms lead to? At first, I thought it was meningitis, but he doesn't have a stiff neck ... I'm completely lost.

Also, we found through Gram-Staining that he has numerous PMNs (polymorphonuclear cells) and many gram-positive cocci as single cells, in pairs, and in clusters. A blood test was negative. —Preceding unsigned comment added by 69.16.95.123 (talk) 11:39, 15 April 2010 (UTC)

Please do your own homework.

Welcome to the Wikipedia Reference Desk. Your question appears to be a homework question. I apologize if this is a misinterpretation, but it is our aim here not to do people's homework for them, but to merely aid them in doing it themselves. Letting someone else do your homework does not help you learn nearly as much as doing it yourself. Please attempt to solve the problem or answer the question yourself first. If you need help with a specific part of your homework, feel free to tell us where you are stuck and ask for help. If you need help grasping the concept of a problem, by all means let us know.

Ah, come on, he has "attempted to solve the problem himself", and is stumped. What more can we expect him to do, other than looking through some medical reference book or browsing through random wikipedia articles or something. It seems like an appropriate step to ask for help on-line. I am a bit worried about giving medical advice though, even for a "fake patient". I'll start a thread on the talk page. Buddy432 (talk) 15:00, 15 April 2010 (UTC)

Here's the thread I started. Buddy432 (talk) 15:08, 15 April 2010 (UTC)

(from talk page) Ask, Were thy on any medication prior to admittance? I'm thinking along the lines of discounting any adverse drug reaction, especially the rarer ones caused by to or more drugs. --Aspro (talk) 15:16, 15 April 2010 (UTC) —Preceding unsigned comment added by Buddy432 (talk • contribs)

Has Dr House told you what he thinks yet? He is usually wrong on the first couple of tries. Googlemeister (talk) 16:03, 15 April 2010 (UTC)

... and don't forget that it's never lupus - except when it is. Gandalf61 (talk) 16:38, 15 April 2010 (UTC)

I'd not discount meningitis just on the absence of one symptom. It's too severe an infection to discount like that. Also, there are symptom sorters available online (yourdiagnosis.com) or in written form. Have you also ruled out measles or rubella?

Your first paragraph includes symptoms that could result from a range of diseases, including infections, vasculitis, and systemic inflammatory processes. However the presence of numerous gram positive cocci is a giveaway. This is almost certainly either Streptococcus or Staphylococcus. The clusters are more suggestive of Staphylococcus; the most likely cause is Staphylococcus aureus septicaemia. Axl ¤ [Talk] 20:22, 15 April 2010 (UTC)

You make a very good point; the previous post makes a very good point also, about not discounting meningitis just on the absence of one symptom. It goes therefore, without saying that ”Time is of the essence”, and this is not the time to discuss the evils of over proscribing antibiotics. BUT what does one do (now, at this very moment)? The word 'many', as in “many gram-positive cocci as single cells, in pairs, and in clusters” is not a truly objective, any more than anything else said - (pictures would have been nice). So does one give a gram antibiotic? Time may be running out.--Aspro (talk) 21:19, 15 April 2010 (UTC)

Well, I thought that the OP was asking for help on the (fake) diagnosis. So you want to know about treatment? Axl ¤ [Talk] 07:45, 16 April 2010 (UTC)

So taking into account Axl's putative diagnosis of Staphylococcus aureus septicaemia, test for methicillin resistance in case this is MRSA: if so, find an antibiotic that works and start therapy pronto! --TammyMoet (talk) 21:00, 16 April 2010 (UTC)

DNA Bases

Why are the bases in DNA/RNA said to be hydrophobic if they can form hydrogen bonds? —Preceding unsigned comment added by 67.177.181.221 (talk) 14:06, 15 April 2010 (UTC)

Are they hydrophobic? Do you have a source for that. Looking at the structure, I would think they would be fairly hydrophilic; their presence in the cytoplasm (which is mostly water) would indicate that they aren't. Indeed, if they were hydrophobic, I would expect them to cluster or agglomerate in such a way as to make them not work as they do; the fact that they exist free-floating in the cyctoplasm indicates to me that they aren't hydrophobic. I could be proven wrong, but where is the assertion that they are? --Jayron32 14:56, 15 April 2010 (UTC)

Electrolysis

I understand the concept of electrolysis, but what does it mean to apply a voltage? Say a cell that has a net voltage of -2V as indicated by potentiometer (and since -2 is negative, the redox reaction is nonspontaneous.) My textbook says you need to apply -2V to drive this reaction. But shouldn't you apply +2V? I totally don't understand the concept of applying a voltage. —Preceding unsigned comment added by 142.58.43.216 (talk) 16:31, 15 April 2010 (UTC)

Some people like to think of electricity in terms of the Hydraulic analogy where voltage (or "potential difference") is compared to pressure of a fluid. One connects anything that might pass current to a voltage source (such as a battery) by two wires, just like in the analogy one connects to a pump by two pipes for forward and return flows. The negative terminal of a voltage source is the one where there is a surplus of electrons. Cuddlyable3 (talk) 17:02, 15 April 2010 (UTC)

Yea, the sign doesn't really matter. 2V just refers to the differential between the two wires. Depending on which wire is positively charged and which is negatively charged, the electrons will flow one way or the other, and this is what the + and - show. However, the anode and cathode should be made of different materials for electrolysis, so you do need to know which gets connected to the positive and negative terminals. StuRat (talk) 18:42, 15 April 2010 (UTC)

No, the materials need to be of different materials if you are making a galvanic cell. For an electrolytic cell, just about any inert conductor will do fine. They can be the same material. --Jayron32 19:08, 15 April 2010 (UTC)

My question is still not answered. Why does it not matter if you apply a + or - voltage? In electrolysis, it should matter because the natural voltage between two nonspontaneous redox reactions should be negative. My incomplete understanding of this is making it hard for me to further understand the basics of voltammetry. —Preceding unsigned comment added by 142.58.43.94 (talk) 19:31, 15 April 2010 (UTC)

In electrolysis, the two electrodes are in the same solution. So it doesn't matter whether the electrode in your left hand has the higher voltage or the one in your right one does. The process will happen the same either way; the only difference will be at which electrode the oxidation process goes on and at which one the reduction process goes on. However, the sign of the voltage is merely directional. It only tells you whether electrons are flowing in or out of that particular electrode. The actual process will occur regardless of the direction; the only difference will be which half-reaction will take place at which electrode. --Jayron32 19:56, 15 April 2010 (UTC)

(after edit conflict) ::::A voltage is just a potential difference between terminals. Whether you call it +2V or -2V depends on how you measure it. As mentioned above, for electroysis, the + side of your voltage source goes to the anode, and the - to the cathode. The anode is +2V with respect to the cathode, or you could say that the cathode is -2V with respect to the anode. If anode and cathode are the same material, then it doesn't matter which is which, but the direction of the electrolytic separation will depend on the direction of the current, and this depends on which side is positive and which side is negative. Traditionally, current flows from + to - but negatively charged ions will flow the other way. Dbfirs 20:05, 15 April 2010 (UTC)

sodium carbonate

does sodium carbonate (soda ash) degrade when exposed to air? or does it remain corrosive? —Preceding unsigned comment added by Jonny12350 (talk • contribs) 18:41, 15 April 2010 (UTC)

It depends on which sodium carbonate you mean. Sodium carbonate exists naturally in several different hydrated forms, see Sodium_carbonate#Occurrence. I am pretty sure they are all fairly stable for any reasonable amount of time. Pure, unhydrated sodium carbonate is likely somewhat hygroscopic, so you can likely generate one of the hydrate forms if you leave it out on a humid day for some time. And acid will tend to degrade the sodium carbonate first to sodium bicarbonate then to carbonic acid; the latter of which is metastable and decays quickly to carbon dioxide and water. But if kept dry and in a sealed container, I think that sodium carbonate can keep indefinately. --Jayron32 18:59, 15 April 2010 (UTC)

im talking about the kind you buy in the store for cleaning. its not in a sealed container but rather in a pile on the counter —Preceding unsigned comment added by Jonny12350 (talk • contribs) 19:45, 15 April 2010 (UTC)

In that case, its cleaning properties are largely because it is abrasive and not corrosive. In other words, its gritty, and so tends to break dirt and stains up into smaller bits to make them easier to wash away. It is slightly alkali in nature, so it will saponify any oil-based dirt, to a small extent, which also helps. Due to the ion exchange effect, it can, like all ionic salts, speed the corrosion (rusting) of iron much like ordinary table salt (sodium chloride) does, so I would rinse it off any metal surfaces you cleaned with it; but by itself it isn't usually very corrosive. Douse with water and follow with several wipes with a damp sponge, and your metal surfaces should be fine. --Jayron32 20:04, 15 April 2010 (UTC)

It may react with atmospheric carbon dioxide to form sodium bicarbonate, but that shouldn't affect its cleaning or water softening abilities. --98.221.179.18 (talk) 00:37, 17 April 2010 (UTC)

April 16

The mass of something 1836 times smaller than you?

An electron is only 1,1836 the mass of a proton. If your mass was 50 kilograms, what would be the mass of something 1836 times smaller than you? Try it the other way. What would be the mass of something 1836 times larger than you? —Preceding unsigned comment added by BlackBerryStromGuy (talk • contribs) 00:51, 16 April 2010 (UTC)

Not sure what you're asking here, but this appears to be simple arithmetic. If you weigh 50kg something that's 1836 times smaller than that weighs 50/1836 kg (about 27g or call it give or take 1Ounce. Something 1836 times 50kg is 50 * 1836 kg or about 90 tons. Call it about 19 elephants. Tonywalton ^Talk 01:07, 16 April 2010 (UTC)

This reads like a homework question, yet it makes no sense as a homework question to me. Why did you need to know this? Vimescarrot (talk) 10:44, 16 April 2010 (UTC)

Neutrons have slightly more mass than protons and I have plenty of them in me, how is it on your planet? Cuddlyable3 (talk) 12:33, 16 April 2010 (UTC)

I simplified the title for reference. Cuddlyable3 (talk) 19:30, 16 April 2010 (UTC)

Internet searches for non-linear notations

Please see Wikipedia:Reference desk/Computing#Internet searches for non-linear notations. -- Wavelength (talk) 01:21, 16 April 2010 (UTC)

Icelandic volcano and air travel.

So - just how long could the volcano in iceland keep aircraft from flying over the UK? Some sources say that the wind could change direction - like that would solve the problem...but couldn't this think keep on belching dust for a very long time? Just how long could it keep going? Days? Weeks? Months? Years? SteveBaker (talk) 02:21, 16 April 2010 (UTC)

This article quotes a volcanologist at the University of Edinburgh as saying that the eruption could last years. As for disruption of air traffic, it will very much depend on the direction of the winds aloft. After British Airways Flight 9 and KLM Flight 867, the aviation industry is very concerned about flight though volcanic ash clouds. -- Flyguy649 ^talk 02:38, 16 April 2010 (UTC)

If it keeps going for years - the wind is going to cause this kind of chaos several times a month for all that time? That would be kinda annoying! SteveBaker (talk) 02:54, 16 April 2010 (UTC)

Yup. Rio de Janiero might become a big hub for Europe-North America air traffic! -- Flyguy649 ^talk 02:56, 16 April 2010 (UTC)

And US-Europe cruiseships may see a revival. caknuck _° needs to be running more often 06:21, 16 April 2010 (UTC)

(Western/Nothern) Europe is perhaps somewhat fortunate that they have decent high speed rail for intra Europe travel which may get a further boost if this disruption continues. BTW, [8] suggests that repeated disruptions are definitely possible. Incidentally, as someone who just purchased something from Germany and paid a lot for shipping to because of $#(*&%!* Deutsche Post/DHL's we don't price by weight for packets policy the disruption is rather annoying. Nil Einne (talk) 07:23, 16 April 2010 (UTC)

Epic: "Ladies and gentlemen, this is your captain speaking. We have a small problem. All four engines have stopped." --Sean 16:52, 16 April 2010 (UTC)

Cool animation of the ash plume from the ESA. -- Flyguy649 ^talk 09:52, 16 April 2010 (UTC) We can survive cancelled commercial flights for a while but there are other emergency aviation needs such as air ambulances, mountain rescue and forest firefighting. Would a battery powered electric helicopter be a feasible solution at this time? Cuddlyable3 (talk) 12:27, 16 April 2010 (UTC)

Battery powered helicopters can barely support their own weight. But you could use a helicopter with internal combustion and a filter (like a car engine basically), instead of a jet engine or turbine. And I think most non-military helicopters are internal combustion. Also, fly low, under the plume. Ariel. (talk) 12:51, 16 April 2010 (UTC)

Au contraire. See the "Hexacopter," which can carry itself plus a substantial payload. Would the size/mass problem that defeated Langley prevent its being scaled up? Edison (talk) 20:09, 16 April 2010 (UTC)

Because the eruption was largely unexpected, the safest course of action in the short-term was to simply cancel all flights in affected areas and put up with the inconvenience and economic losses. If the hazardous conditions exist for a few more days, flight plans will be developed to avoid the affected areas. If conditions last for a few more weeks, safety assessments will take place and flight procedures will be developed that fly in the affected areas but minimize the risk. If the hazardous conditions really do last "several years", then we will have time to develop engineering fixes to the flight control electronics, engine intakes, and so on, to accomodate the non-ideal conditions and safely fly through zones with large amounts of volcanic ash. This is really a matter of estimating how much effort should go into developing solutions for a problem which might be temporary anyway. If global dispersion of volcanic ash becomes the most serious impediment to air travel over the next several decades, we will see engineers developing revolutionary new kinds of aircraft that are impervious to ash plumes - but that would only be worthwhile if the consequences of volcanic eruptions are huge. Nimur (talk) 15:35, 16 April 2010 (UTC)

Engineering fixes seem difficult at best. Aircraft that have flown through ash plumes in the past had all of the paint scoured off the plane and the windows 'sandblasted' to the point where it was impossible to see out! The very nature of jet engines is that:

• They take in a lot of air at high speeds...filtering that air is not a possibility.
• They burn fuel at temperatures high enough to melt the tiny rock fragments in the ash and turn it into the sticky glassy substance that then coats the internal parts.
• That the fuel burns at a temperature that's high enough to melt the engine parts themselves if there isn't a cooling airflow ducted in through narrow holes that get blocked by the ash.

It's not going to be easy (and perhaps not even possible) to fix those things. SteveBaker (talk) 18:14, 16 April 2010 (UTC)

Why couldn't air routes be lowered to fly under the plume? (High mountain areas excepted). Certainly it would be louder for those on the ground. How much would fuel consumption go up at say 10,000 feet (3000 meters) rather than 30,000 feet (9100 meters) or whatever is the favorite altitude for passenger jets? Edison (talk) 20:11, 16 April 2010 (UTC)

Because a) debris is constantly precipitating out of the debris cloud and b) this would require constant monitoring of the ash cloud ceiling (which can vary greatly locally) over an area of tens of thousands km². Better to go around than under. caknuck _° needs to be running more often 22:16, 16 April 2010 (UTC)

Black lights, wattage, and wave lengths

I have some glow in the dark powder pigment, specifically this that I use sometimes, and have been using a 75 watt GE black light bulb to charge it. I also have a 3W led UV light. The led operates at 395-400 nm wavelength, I think the 75W is at 365. Any ideas about the differences is the effectiveness of charging the powder? Using the flashlight is vastly preferable but not at a huge sacrifice to a brightness from the powder. Beach drifter (talk) 03:20, 16 April 2010 (UTC)

You need a certain wavelength to charge it. A longer wavelength will not charge it at all, and a shorter one just wastes energy. Once you have that wavelength, the brighter the light the faster it will charge (more or less). To find out how bright the bulb is, in theory you want the lumen or candela, but those are adjusted to human vision, and UV does not rate. Electrical watts tells you very little since you don't know how efficient the bulb is (unless they are both the same type, you did not specify). Confusingly, Radiant flux is also measured in watts. So are those electrical (input) watts or radiant (output) watts? Note: the powder could be a mix, and might have multiple desired wavelengths, but I think pure green isn't a mix. Ariel. (talk) 04:01, 16 April 2010 (UTC)

I'm fairly certain the powder is not a mix, it is very strong, pretty awesome stuff. The 75W bulb is an incandescent type that you can get at Walmart. The down side is that it gets very very hot and when camping requires a dc to ac converter and a car. Beach drifter (talk) 04:12, 16 April 2010 (UTC)

I think that Incandescent UV bulbs are ordinary bulbs with filters that remove visible light. The UV efficiency is probably horrible (but I don't have numbers). So despite being 75 watts little UV is made. But probably more than 3 watts worth. Can you do a test, just because I'm curious? Try to charge the powder with a regular 75 watt bulb. Anyway, what I would suggest for you is a 12 volt portable fluorescent lamp with a built in battery. Car mechanics use them, so it should not be hard to find. Ariel. (talk) 21:32, 16 April 2010 (UTC)

Palatine uvula

I read the article on this but didn't find the answer I was looking for. My query is: other than humans, do other animals have a uvula? If so, what it it used for since humans use it for language? —Preceding unsigned comment added by 99.250.117.26 (talk) 04:21, 16 April 2010 (UTC)

It is adapted by humans for use in language. Its other purpose is to close off the nasal sinuses from the throat, to prevent food from getting into your sinuses when you swallow. See also Epiglottis for a similar flap covering the trachea. --Jayron32 04:29, 16 April 2010 (UTC)

How does the uvula, which exists in the oropharynx, prevent food from getting into the sinuses, which communicate with the nasal antrum? DRosenbach ^{(Talk | Contribs)} 05:02, 16 April 2010 (UTC)

Look at the pictures in either of the two articles you linked. There are two flaps at the top and bottom of the pharynx. The top is the uvula and the bottom is the epiglottis. During swallowing, both flaps are pushed away, blocking the relevent openings to either end of the breathing system. --Jayron32 05:21, 16 April 2010 (UTC)

Both pictures are midsagittal planes, rendering 2D images of 3D objects. DRosenbach ^{(Talk | Contribs)} 18:56, 16 April 2010 (UTC)

My original question does not seem to be answered: do other animals have a palatine uvula? If they do, then I assume that it has the same function of closing off the nasal passage during swallowing since no other animal seems to have the same sophisticated vocal language that we humans do. —Preceding unsigned comment added by 69.77.185.91 (talk) 16:57, 16 April 2010 (UTC)

Do plants need to sleep?

Is it healthy for plants to be out in the sunlight all day and then under a fluorescent light at night? Should they be left in the dark to sleep? Do they need to sleep? Specifically I was wondering about very young pumpkin plants. For the hell of it, I just started a couple plants in pots [soup tins].--Brianann MacAmhlaidh (talk) 06:49, 16 April 2010 (UTC)

From what I read after a google search it seems that the leaves will grow OK, but the constant light will mess with flower budding, and other plant stages. So you might get a big plant, but no pumpkins. You might be able to start with constant light and grow them fast, then switch to a normal pattern when it's time for flowers, but I'm not sure. In general plants use the ratio of dark to light to know what season it is, and they do different things at various points in the seasons. Ariel. (talk) 08:28, 16 April 2010 (UTC)

It depends on what type of photoperiodism your plant exhibits. Pumpkins are in the same family (taxonomy) as cucumbers, which according to our article are day-neutral i.e. they will flower in any light regime. I don't know whether this carries over to to pumpkins, or whether other physiological processes will be affected by constant light. 131.111.185.69 (talk) 09:26, 16 April 2010 (UTC)

Refractive index less than one

In Refractive index it says: "Contrary to a widespread misconception, n may be less than 1, for example for X-rays." But doesn't that imply a speed of light greater than c? The only thing I could think of is that for X-rays this is "n" as compared to air, not vacuum. Ariel. (talk) 08:20, 16 April 2010 (UTC)

The phase speed is greater than c, but that doesn't mean that a signal can be sent with such speeds. Remember that an idealized monochromatic wave actually extends to infinity (only then the Fourier transformation yields a single frequency). The propagation of a wave packet will be slower. Icek (talk) 11:02, 16 April 2010 (UTC)

To be more specific, the speed of light in a medium is actually given by

$v_{g}={\frac {c}{n-\lambda {\frac {dn}{d\lambda }}}}$

which will always be smaller than (or equal to) c even when n<1. Dauto (talk) 15:12, 16 April 2010 (UTC)

The Leaning Brown Building of the Spanish Steps

Photo A

Photo B

In Photo A, the brown building on the left seems to be standing perpendicular to the ground, as you’d expect.

But in Photo B it’s very different. Obviously it’s a function of where the photographer was standing and the direction the camera was pointing. The vanishing point seems to be a foot above the picture, yet the camera was clearly not aimed at the vanishing point. How to explain the effect? -- Jack of Oz ... speak! ... 10:48, 16 April 2010 (UTC)

Perspective distortion (photography)? It looks in the second camera as if the person is tilting the camera up slightly (unless that's just my eyes) which can have the affect of making buildings lean/slope in funny directions. 194.221.133.226 (talk) 11:11, 16 April 2010 (UTC)

The metadata for the left photograph indicates it has been treated in Corel Paint Shop Pro where it could have received perspective correction to make the vertical edges of buildings parallel. Cuddlyable3 (talk) 12:09, 16 April 2010 (UTC)

Looks to me like the photographer was tilting the camera up in the second picture. The fountain in the foreground also looks wrong. Take a look also at a tilt shift lens. Ariel. (talk) 12:30, 16 April 2010 (UTC)

The second image was shot up the hill without perspective correction, either with a tilt-shift lens or via software. Since there's an angle upwards, the vertical lines will converge in accordance with the principals of perspective. Our brain tends to edit out such vertical perspective, but not horizontal perspective, which we expect as a natural phenomenon. Therefore, pictures that exhibit vertical perspective look odd. It's the bane of architectural photographers, since most buildings are taller than the photographer, so shooting up, if one is reasonably close, is inevitable. I routinely correct for vertical perspective in Photoshop, since I haven't brought myself to spend on a nice T-S lens. The Spanish Steps are on a steep hill, so the vantage point of the first image, off to the side, avoids the problem to some degree (anmd appears to have been further fixed in Corel), while the second is significantly lower than the base of the steps. Acroterion _(talk) 17:21, 16 April 2010 (UTC)

For answering questions like this, you may want to post a link from the Featured Pictures talk page. Those guys are experts at correcting and understanding all kinds of distortion effects. 64.235.97.146 (talk) 18:19, 16 April 2010 (UTC)

brain activity and dreams

Every action of ours is ordered by our brain. In dreams, if we do any action like eating, fighting etc., it is because of the brain's activity or our obeying the brain's order, of course mentally. In that case, why is the body in reality not obeying the order of the brain (i.e. why don't we eat or fight, waking up from sleep, as a result of the 'order' from our brain) ? And if it does, like in case of somnambulism or something like that, we call it a 'disorder'. Another question is that why don't most of us remember the dream that we dreamt that particular night, at once after waking up. (i would rather prefer to be a fool asking questions that are foolish) —Preceding unsigned comment added by 125.21.50.214 (talk) 11:16, 16 April 2010 (UTC)

I'm not an expert here, but I know there are different segments of the brain. One bit is controlled consciously, another is automatic. Dreams are a result of, I suppose, random thoughts being viewed. Most people do remember their dreams, but stress and other factors can cause us to forget. If we disobey the orders of the brain, we get tired, hungry, or injured. That's all I can help you with. Maybe there are some experts here. 2D Backfire Master ^{sweet emotion} 11:21, 16 April 2010 (UTC)

Sleep paralysis. During sleep the body "switches off" the nerves that would otherwise carry out the actions. If they don't switch off, then you have Sleep walking. And sometimes it will stay switched off for short time after waking, which is quite terrifying when it happens. (It's happened to me twice.) Ariel. (talk) 11:38, 16 April 2010 (UTC)

Wow, that sleep paralysis article is awful. I think it's talking about 2 different things and doesn't even know it. Comet Tuttle (talk) 20:43, 16 April 2010 (UTC)

Yeah, as the sleep paralysis article explains (although not very clearly), there is a special circuit in the brainstem that disconnects the upper brain from the lower motor centers during the dreaming state. In experiments using cats where this small brain area was damaged, the cats would physically enact their dreams. There is a caveat though: sleepwalking is actually a different phenomenon. The data is limited, but it looks like a sleepwalking person is not actually in the dreamlike state, but rather in a state where part of the brain is asleep while other parts are awake. Looie496 (talk) 17:45, 16 April 2010 (UTC)

Michel Jouvet is famous for his experiments in which he destroyed a portion of the lower brain stem in cats that caused paralysis during sleep; some cats then could be seen to act out their dreams. Until, presumably, they were woken up by all the tactile input of walking around. A quibble with your first statement: Not every action of yours is ordered by your brain. Healing, most (or all?) of the digestion process, and several kinds of reflexes are examples. Comet Tuttle (talk) 20:43, 16 April 2010 (UTC)

Why can't plants move?

What in evolution made plants immovable? They prepare their own food but is it 'food' all they need? They depend on wind, insects, water etc., for pollination, they would have been lot more better (than the highly-evolved humans) had they been able to move since the time of evolution. - Anandh, Chennai —Preceding unsigned comment added by 125.21.50.214 (talk) 12:07, 16 April 2010 (UTC)

How could they both move and have roots? I think once they have roots, they are committed to it. If you mean move branches, some plants do, but most of the time it's not very useful for a plant to be able to do that. Ariel. (talk) 12:14, 16 April 2010 (UTC)

Some plants are capable of rapid movement. See venus flytrap. As an aside, movement takes a LOT of energy, so there needs to be a really good reason to evolve such a capability. In the case of the venus flytrap, it lives in such poor soil it needs to catch bugs for nutrients. --Jayron32 12:41, 16 April 2010 (UTC)

See Rapid plant movement for a lengthier list. Gabbe (talk) 13:04, 16 April 2010 (UTC)

It is also important to think of plant movement speed based on plant lifespan. Consider a plant that can live for 1,000 years. If it moves a branch a couple feet in a year, that is relatively fast movement/lifespan compared to animals. Another way to think about it: Animals have a very short lifespan compared to plants. So, they have to quickly find food. Plants have time to wait for food. -- kainaw™ 12:46, 16 April 2010 (UTC)

Not really. Even if you assume a human is only going to move 50 years, he would only be able to move 20 yards a year, and that is incredibly slow. I bet even a snail could beat that in a week or two. Googlemeister (talk) 13:41, 16 April 2010 (UTC)

One might as well ask why humans can't generate their own food by just sitting in the sun, as that would clearly be a lot easier than running around and trying to brain other creatures with stones. --Mr.98 (talk) 12:48, 16 April 2010 (UTC)

See tumbleweed, sargassum and phytoplankton.--12:56, 16 April 2010 (UTC)

Photosynthesis doesn't really generate enough energy to move around like us animals do. If plants wanted to move and dance under their own power they'd need to find a new source of energy.

The Venus Fly Trap mentioned above can take hours or even days to "reset" its traps. APL (talk) 14:51, 16 April 2010 (UTC)

Who says that having movment means something is higher evolved? If you ask me, plants were here before humans and have evolved to make their own food, be self sefficient during a regular life cycle and reproduce by using the natural occurences of the Earth. If you ask me, they are much higher evolved. 74.218.50.226 (talk) 15:44, 16 April 2010 (UTC)

That debate came up while back when the DNA of rice was completely sequenced. Previously, there was an assumption that dna sequence length equated to level of evolution. However, rice sequence length is much longer than human sequence length. So, I saw some people assume that the rice sequencing was wrong and they wanted to resequence it to see if was actually much shorted. Others assumed human sequencing was wrong and wanted to resequence it to make it longer. Some assumed that equating evolution level to sequence length was hogwash and dropped that whole idea. A few wacky scientists said that it was all correct and that rice was more evolved than humans. As one put it: Try living all year standing knee-deep in a cold bog and see how long you survive. -- kainaw™ 15:49, 16 April 2010 (UTC)

The first plants to appear were algae. They floated in the sea, carried by currents, getting nutrients from the surrounding water and using sun energy from the sun. They were no animals yet, so they couldn't feed from them. There was no oxygen in the atmosphere yet, so they couldn't use it to make the energy transformation that us animals use now. Time passed, and algae filled the oceans and increased the oxygen content in the atmosphere. Some of the oxygen dissolved in the sea water. Now some pluricelled (is that the name in english?) livings discovered a mean to eat the algae and use the oxygen to process its components into lots of energy. Algae couldn't have discovered that process because the ingredients weren't there when they first appeared. All plants descend from those algae, and all animals descend from those algae-eaters. Our ancestors went down that path of evolution and we are pretty much stuck into it, for good or for bad. There are some very successful species that decided to test new grounds (like fish becoming amphibian when they first went to land, and later some big land animals deciding to return to the sea and becoming whales) but they still carry an awful lot of inherit traits, and they needed a lot of generations and ambient influences to change their shapes. --Enric Naval (talk) 16:50, 16 April 2010 (UTC)

Multicellular? Zain Ebrahim (talk) 17:00, 16 April 2010 (UTC)

In English, we call it a multi-celled plant or animal. StuRat (talk) 17:02, 16 April 2010 (UTC)

Mind controlling gene function.

A person's character is based on genes (excluding environmental factors)(they say...like father/mother is the son/daughter)but character changes as years pass by. Does that mean the gene expression or gene function for the 'disappearing character' lost/stopped? If so, can one's mind control the gene expression so that it would be advantageous for one to evade baldness, fear etc., by controlling the baldness/fear gene's expression/function ? - anandh, chennai —Preceding unsigned comment added by 125.21.50.214 (talk) 12:26, 16 April 2010 (UTC)

Are you sure "A person's character is based on genes" is true? It's probably affected to some degree by it, but not controlled absolutely. This is a very very old argument, with no single answer, but you can read all about it in Nature vs. Nurture. Ariel. (talk) 12:32, 16 April 2010 (UTC)

Yes, son/daughter has father/mother's character. The reason obviously is through inheritance (genes of course). It hence means genes control characters, though not absolutely as mentioned by Mr. Ariel. - anandh, chennai —Preceding unsigned comment added by 125.21.50.214 (talk) 12:54, 16 April 2010 (UTC)

How can you be certain that sons & daughters don't have their mothers/father's character because they were raised by their mother/father and so learned that personality. What percentage of their character is because they have their parent's genes, and what percentage is because they were raised by their parents? --Jayron32 13:55, 16 April 2010 (UTC)

Agreed. Genes are a minor factor, with environment being the major factor, and there's also a small random element (we know this since identical twins raised together aren't quite identical in personality). Now, as for the genetic part, yes, they can express at different ages. For example, sexual orientation may not express until puberty or even later. However, this certainly doesn't mean that this gene expression can be controlled by conscious thought. StuRat (talk) 16:56, 16 April 2010 (UTC)

"son/daughter has father/mother's character". This proposition implies that all siblings have the same character. That's certainly not true in my experience, and in the US we have somewhat of a tradition of presidents with ne'er-do-well relatives. --Sean 17:06, 16 April 2010 (UTC)

When you talk about the mind controlling gene expression, you are improperly mixing levels in a way that can only lead to confusion. There are many factors that influence gene expression, including levels of stress-related hormones such as cortisol. Since stress is clearly a function of cognitive factors, there must be at least some degree of influence of cognitive factors on gene expression. It is important to point out, though, that a gene that is not expressed does not disappear -- it is still there, and will still be inherited. Also gene expression often differs greatly for different cells within a single body. Looie496 (talk) 17:36, 16 April 2010 (UTC)

Stephen Pinker has argued that behavioral studies tend to underplay the role that genetics has on behavior. Studies that show, for example, that reading to your children before bed boosts their scholastic aptitude don't control for genetics so it could simply be the case that families with genes that lend themselves to scholastic aptitude include the tendency to read to children at night.

Even if one's DNA has a stronger influence on behavior than we normally assume, it doesn't necessarily mean that it's particularly strong (especially when we have very strong environmental factors). In this TED talk, Jonathan Haidt talks about a postulated innate morality but, as he argues, innate doesn't mean fixed. It's just means that there's an existing template that our genes provide that experience then revises. This is also part of Derek Bickerton's language bioprogram theory regarding innate grammar. — Ƶ§œš¹ _{[aɪm ˈfɹ̠ˤʷɛ̃ɾ̃ˡi]} 19:31, 16 April 2010 (UTC)

Genes have essentially no impact on your character. They might on your intelligence etc, but a son of two really popular and charismatic people might be a real loner who is afriad of social interaction simply due to the fact that he's never learned how to act appropriately in social situations (I know a guy like this with parents like that). Also twin studies are rubbish, the twins do not go through identicle upbringings. It would be exceptionally naive to assume they do. Siblings, twins, often have different interests and do loads of different things. One twin might be a great footballer and become a PE/Gym teacher. The other may be more academically orientated and go on to be some brilliant proffessor.--92.251.148.126 (talk) 22:50, 16 April 2010 (UTC)

Map of the world folded along the equator

Where could I find a map of the world where the southern and northern hemispheres are superimposed, so that the same latitude north and south of the equator is shown in the same place? This results friom a discussion on the Entertainment Desk about how far south Australia is compared to how far north Europe is. Thanks 78.151.110.54 (talk) 16:33, 16 April 2010 (UTC)

There's a couple in our antipodes article. See also www.antipodemap.com --Shantavira|^{feed me} 16:46, 16 April 2010 (UTC)

Let's split...

Which came first, the split between plants and animals or the split between single-celled and multi-celled ? Since we have all 4 combinations, that implies that one of those splits happened twice. Here is are some possibilities I see:

SP = Single celled Plants
MP = Multi-celled Plants 
SA = Single celled Animals 
MA = Multi-celled Animals

SP -> MP -> MA -> SA

MP                
^              
|
SP -> SA -> MA

StuRat (talk) 17:14, 16 April 2010 (UTC)

I think Multicelularity evolved more than once but I don't think SP -> SA makes any sense. Dauto (talk) 18:23, 16 April 2010 (UTC)

So then do you think that single-celled animals (de)evolved from multi-celled animals ? StuRat (talk) 19:24, 16 April 2010 (UTC)

More relevant, I think, is the monophyly of Eukariotic life. Having organelles within your cell structure isn't necessarily a prerequisite to multicellularity, but it certainly helps. — Ƶ§œš¹ _{[aɪm ˈfɹ̠ˤʷɛ̃ɾ̃ˡi]} 19:22, 16 April 2010 (UTC)

It is not as simple as that. The chloroplasts found in plants are believed to come from unicallular organisms that became part of plant cells during their evolution. And there are things that are neither animals nor plants. I take it that the OP did not study biology at school. 78.151.110.54 (talk) 19:26, 16 April 2010 (UTC)

"Which came first" is hard to answer, because it depends on how you define "plant", "animal", and "multi-cellular". Is a plant "something that obtains energy from non-living sources", or "something that obtains energy from the Sun"? Is an animal "something that obtains energy from its surroundings", or "something that obtains energy from other living things"? Is a multicellular being any grouping of attached cells, only those groupings where the cells interact, or is it further restricted to ones with some degree of specialization of the cells? What does a mat of chemosynthetic bacteria count as? --Carnildo (talk) 22:39, 16 April 2010 (UTC)

football effecting brain

does taking heads(in football) harms your brain(means unabling the brain to do something,anything)?

but here is a simple explanation that when u take head there is jerk on ur head so damage is inevitable.

well i don't think so as our brain is well secured in a bony box ie skull and also for further safety there is 3 layered membrane filled with a fluid absorbing shocks.

I THINK IT IS JUST A MISCONCEPTION —Preceding unsigned comment added by Myownid420 (talk • contribs) 17:41, 16 April 2010 (UTC)

Well, you're wrong. The brain has a lot of protection, but it is so soft and squishy that a hard blow to the head can seriously damage it anyway. Looie496 (talk) 17:51, 16 April 2010 (UTC)

I remember reading some time ago that this is a danger and that professional footballers and others were advised to avoid them. Cannot recall where I saw it, but I often look at health section of the BBC news-site, and that would be the sort of thing they'd cover. 78.151.110.54 (talk) 18:38, 16 April 2010 (UTC)

Jeff Astle, one of West Bromwich Albion's most famous players, died from a brain disorder which was ascribed at the inquest to repeatedly heading a football. I would point out, however, that he was active in the 1960s and 70s when footballs were made of leather and became even heavier in wet English conditions. [9] --TammyMoet (talk) 19:19, 16 April 2010 (UTC)

See Dementia pugilistica. At the bottom of the article it notes that it's been diagnosed also in player(s) of American football and professional wrestling. Comet Tuttle (talk) 20:47, 16 April 2010 (UTC)

Yes it certainly does, and those are just the first four google hits. ~ Amory (u • t • c) 20:52, 16 April 2010 (UTC)

Movie about the "representative town in sampling"

I have a vague recollection there is a movie about a town (in US) that was seen for a time as a very representative town, with regards to sampling (it's population was seen as very "average"). Half an hour of googling and looking through Wikipedia categories and articles gives me nothing. Any suggestions? --_{Piotr Konieczny aka Prokonsul Piotrus| talk} 17:54, 16 April 2010 (UTC)

Will_it_play_in_Peoria?#Peoria_as_test_market -- Coneslayer (talk) 17:58, 16 April 2010 (UTC)

Interesting, but I see nothing about a movie. I am pretty sure I read about something similar in the context of a movie made of it (or a book? Hmmm.). --_{Piotr Konieczny aka Prokonsul Piotrus| talk} 18:47, 16 April 2010 (UTC)

Largest Recorded Solar Flare

When was the largest recorded solar flare? According to this, it was recent. But according to this, it was in 1972. --Reticuli88 (talk) 18:46, 16 April 2010 (UTC) The recent one seems to have been measured with a new device. Also, the wikipedia article could be outdated. Most other sources cite the 2003 one. --Cheminterest (talk) 00:46, 17 April 2010 (UTC)

Escape velocity

Escape veocity is said to be the amount of speed necessary to escape an body's gravitationa (or whatever) field. This is usually said to be independent of the launch angle, because kinetic energy is a function of the speed, not velocity, of an object. I think this is a mistake though. If an object were to be launched at an angle to the horizontal, even though it may have the energy necessary to reach an infinity height, its trajectory won't allow it to, because when it reaches its maximum height, it will still have some speed, just perpendicular to the direction of gravity. Am I right? Does the radial component of the velocity have to equal the escape velocity? 173.179.59.66 (talk) 20:11, 16 April 2010 (UTC)

You are right. Wikipedia has an article about Escape velocity. Cuddlyable3 (talk) 23:19, 16 April 2010 (UTC)

But the article indicates that the object will undergo a parabolic trajectory if shot at an angle, which would take it to infinity, no? 173.179.59.66 (talk) 00:18, 17 April 2010 (UTC)

The article is right. The component of the velocity perpendicular to the direction of gravity will steadily decrease as the object moves away from the planet allowing the object to scape. Just remember that the direction of gravity is changing as the object moves along the orbit. Dauto (talk) 01:25, 17 April 2010 (UTC)

beer

i quit drinkin. whats the best tasting brand of non-alcohol beer sold in the usa? —Preceding unsigned comment added by Jonny12350 (talk • contribs) 21:42, 16 April 2010 (UTC)

i found a list of them please choose which i should buy

http://www.wegmans.com/webapp/wcs/stores/servlet/ProductListView?forwardto=ProductListView&Ne=5&Ntt=non-alcoholic%20&langId=-1&Ntk=ProductSearch&storeId=10052&Ntx=mode%20MatchAllPartial&catalogId=10002&N=207&Nty=1 —Preceding unsigned comment added by Jonny12350 (talk • contribs) 21:46, 16 April 2010 (UTC)

This is impossible to answer. The best one for you is the one you like the best (other factors such as cost, availability and so on being taken into account). Put your question another way: "what is the best tomato I can buy"? and you'll see there's no sensible answer. However in my experience (yes, this is original research) all non-alcohol beers are easily describable as "worst". Drink soda or fruit juice instead. Tonywalton ^Talk 00:21, 17 April 2010 (UTC)

The best non-alcoholic beer ? Root beer. StuRat (talk) 01:59, 17 April 2010 (UTC)

Help comprehending units of energy

I can visualize most physical units, for example, I know about how much force a Newton is ("It's like me pressing down this hard"). However I find it very hard to comprehend a joule. Obvioulsy something that is moving has kinetic energy, but how do we quantify it? I am having trouble understanding exactly how much energy a "joule" is, probably because energy doesn't seem like something that one can have "amounts" of. I know this is an extremely hard request but can any of you help me visualize energy?--92.251.148.126 (talk) 23:00, 16 April 2010 (UTC)

Run up a mountain all day without eating. Do you feel hungry? Now you know what energy is. Cuddlyable3 (talk) 23:16, 16 April 2010 (UTC)

Yeah I knew what it was but "how much" is a joule? It doesn't seem to be something quantifiable.--92.251.148.126 (talk) 23:17, 16 April 2010 (UTC)

Why doesn't Orders of magnitude (energy) help? For that matter how about the Calorie? Nil Einne (talk) 00:05, 17 April 2010 (UTC)

I kind of take 92's point. Is it because a unit like a Calorie is defined in terms of other quantities? For example in the definition of the Calorie: the amount of energy required to raise the temperature of one kilogram of water by one degree Celsius one can directly perceive what a kilogram feels like (lift a bag of sugar) and what a temperature rise feels like (OK, perhaps not a 1°C rise, but you can directly perceive a temperature change), but you can't directly feel, see or hear the energy making the change. Tonywalton ^Talk 00:31, 17 April 2010 (UTC)

A joule is defined as the work done when a force of one newton pushes an object one meter, or one coulomb of electrons (a very large number) is pushed through a voltage of one volt. --Cheminterest (talk) 00:50, 17 April 2010 (UTC)

There we are again. The quantities you mention as defining a joule are physically palpable; you can feel a force (whether or not you can accurately tell whether it's 1N) and you can see, or walk, a distance. 92, might the article on Dimensional analysis be of interest? By the way, I'm not sure about your definition of a joule there, Cheminterest; surely the mass of the object you're pushing comes into it somewhere, and isn't work measured per time? Tonywalton ^Talk 01:03, 17 April 2010 (UTC)

c and si

C(carbon) and Si lie in same group.why compound co(carbon mono oxide ) is formed but SiO is not formed .plz explain —Preceding unsigned comment added by 119.154.126.225 (talk) 23:35, 16 April 2010 (UTC)

Actually, it does. See Silicon monoxide. It's just quite rare as it is not very stable (neither is CO, which is why it is not formed in nature. But cars don't burn silicon). Hope this helps, --The High Fin Sperm Whale 00:22, 17 April 2010 (UTC)

That's "quite rare" under normal Earth conditions (we have an atmosphere fairly rich in oxygen, after all, which tends to oxidise most things given half a chance). The article you linked states that "... [SiO] has been described as the most common oxide of silicon in the universe". Wish cars did burn silicon. Stuffing rocks into the tank would be much cheaper than using petrol, and rocks are easier to find than crude oil. Tonywalton ^Talk 00:40, 17 April 2010 (UTC)

About your note about rocks burning silicon: Rocks already contain silicon in an oxidized state. It cannot be burned any more, just like carbon dioxide cannot be burned. An oxidizible silicon compound such as SiO or silane would be a fuel, though. --Cheminterest (talk) 00:52, 17 April 2010 (UTC)

Good point, though CO₂ can be burned; just stuff something hot enough and oxygen-greedy enough into it (a lump of burning magnesium will do the trick, you get magnesium oxide and soot, aka carbon). I wonder if anything cheap could provide enough energy to dissociate SiO₂ in the same way, thus providing silicon out of my car's exhaust pipe which I could sell to Intel or TI. Hmmm...Tonywalton ^Talk 01:17, 17 April 2010 (UTC)

Jets in front of wings

All modern jetliners have jet engines that are placed well in front of the front edge of their wings. Why?