Science desk
< July 25	<< Jun \| July \| Aug >>	July 27 >

Welcome to the Wikipedia Science Reference Desk Archives
The page you are currently viewing is an archive page. While you can leave answers for any questions shown below, please ask new questions on one of the current reference desk pages.

July 26[edit]

Cat bird owl?[edit]

There are so many hoaxes on the internet and on youtube, that I assume this is just pixel animation, but I was curious if it possibly wasn't what the hell is going on in this video where a startled owl stretches out into a cat-like resemblance? Like I said, I'm assuming it's fake until told otherwise, but it's pretty cool looking and there's something about that looked real enough that I thought I'd ask.--70.107.76.121 (talk) 00:24, 26 July 2009 (UTC)[reply]

Okay, now I really want to know just what's being said in these videos. Here's another; same owl type, totally bizarre stuff. Anyone speak Japanese?--70.107.76.121 (talk) 00:30, 26 July 2009 (UTC)[reply]

Some owls have large ears reminiscent of cats. There's no trickery in the first video; I couldn't spare 3:20 to view the second, but both appear to be about owl training. --Tagishsimon (talk) 02:10, 26 July 2009 (UTC)[reply]

I speak Japanese, and all it is saying in the second video is that the owls change shape according to what other owls appear in their vicinity. One changes shape to make it look bigger, signifying 'I am bigger than you' and the other changes shape to make itself look smaller, though the reason is not given. Also, the trainers are using both male and female owls for this experiment/show. --KageTora - (영호 (影虎)) (talk) 02:39, 26 July 2009 (UTC)[reply]

I definitely agree that the video is legit. It's a defensive response. The purpose might be to disrupt a potential predator's search image. Sifaka ^talk 05:15, 26 July 2009 (UTC)[reply]

Searching Japanese Wikipedia for アフリカオオコノハズク leads to Northern_White-faced_Owl although the English article doesn't mention its ability to change its shape like that. The Japanese article seems to have a bit more information but I don't know what it says. Rckrone (talk) 05:39, 26 July 2009 (UTC)[reply]

Am I the only person here who finds that transformation to be fairly unsettling - on a visceral level? --Kurt Shaped Box (talk) 07:14, 26 July 2009 (UTC)[reply]

If it's to deter predators, as suggested above, then that's probably the intention - ie to look like a bag of bones and sinew and not a very good meal.83.100.250.79 (talk) 08:51, 26 July 2009 (UTC)[reply]

Specifically, it's something about the way that the owl's face and eyes appear to change shape that trips off a feeling of 'wrongness' somewhere within me. --Kurt Shaped Box (talk) 09:10, 26 July 2009 (UTC)[reply]

It's all very simple. The owl has a face just like we do. It has muscles that change shape. The owl got scared (but not enough to fly away), so he shrunk away from the jack-in-the-box. The difference is, the owl is covered with feathers. Muscles retract, feathers go with it, and it's face changes shape significantly. If your face was covered in feathers it would be quite a sight when you got shocked, too. Vranak (talk) 17:15, 26 July 2009 (UTC)[reply]

Aye, birds' faces can be very expressive at times, despite being covered in feathers. I don't know if we could pull off 'curiosity' or 'anticipation' when similarly covered. A Budgerigar (for example) can. --Kurt Shaped Box (talk) 20:16, 26 July 2009 (UTC)[reply]

In the second video, the narrator said that it elongates its body to appear as a tree or branch. It squints its eyes so they are less visible. -- penubag (talk) 09:08, 28 July 2009 (UTC)[reply]

Light energy[edit]

Light is frequencies of energy that the eye can see.Frequencies in the blue light field will create a magnetic field. Other levels will create cold temperatures. Who can help me prove this?

Light is not "frequencies of energy" - it is "frequencies of electromagnetic waves", usually referring to those frequencies we can see with the human eye. All light has both an electric field and a magnetic field because light is an electromagnetic wave. Light does not "create" a magnetic field. It is a wave phenomenon which includes a time-varying magnetic field. This has been proven many times by many different methods. See wave-particle duality for more on this topic. I am not sure what you mean by creating cold temperatures; do you mean laser cooling? Nimur (talk) 04:14, 26 July 2009 (UTC)[reply]

Your first phrase reminded me of St. Elmo's fire, but that works the other way round. The light is due to the electric field.71.236.26.74 (talk) 04:23, 26 July 2009 (UTC)[reply]

Is it common to imagine that puffins are bigger than they are?[edit]

I saw a puffin in real life not so long ago. I was surprised at how small it was. When you see them on wildlife shows on TV, they look much bigger. I was expecting something about the size of a medium sized penguin. --84.69.249.254 (talk) 07:29, 26 July 2009 (UTC)[reply]

On TV they are trying to show as much detail as possible, so they'll do close-ups. It's not uncommon to imagine stuff you haven't seen in real life as larger than it is. I still run into rivers that I only used to know from maps and am frequently underimpressed with the width of them. Very few held up to my idea of what a well known river should look like. As for animals, there's an anecdote about Malaria researchers showing a film about mosquitoes to some villagers in Africa and being told that there was no danger because the local mosquitoes never got as big as the one in the film. So apparently the effect isn't unheard of nor limited to puffins. 71.236.26.74 (talk) 08:07, 26 July 2009 (UTC)[reply]

Antarctic penguins suffer similar size-inflation. Television documentaries film the penguins via telephoto lenses, because they are not allowed to approach the birds (environmental and wildlife protection mandates are very strict in Antarctica - though how they are enforced is always a mystery to me). The result is a shot of birds against a barren, treeless ice landscape. With no measure of perspective, these birds appear huge - I always thought the Emperor Penguin would tower above an upright 6-foot human; but in fact the largest of them are only about four feet tall. But from these sorts of photos, how can you possibly tell? The only objects available for visual height reference are... other penguins. For all you know, those penguins could be twenty feet tall. Similar issues plagued the Apollo moon landers - without visual cues about height, it was very hard to tell pebbles from boulders; small holes from large holes; bumps from mountains; depressions from canyons. Human visual perception relies very heavily on the subtle peripheral clues to help judge perspective, distance, and size. Nimur (talk) 18:56, 26 July 2009 (UTC)[reply]

FWIW, when I was a kid, I used to think that the Emperor Penguin was about the same size as a human - a similar height to the extinct Anthropornis (I was just reading about that), I guess. I also imagined the Wandering Albatross as being man-sized, when stood up straight. --Kurt Shaped Box (talk) 12:55, 27 July 2009 (UTC)[reply]

The angle the photo is taken from gives a slight clue about size - a twenty foot tall penguin is likely to be photographed from below, any other angle implies it is smaller. (The horizon usually marks where human eye level is, on all objects in the photo, in flat terrain.) And I share the puffin experience - when I first saw one next to a person I was disillusioned and disappointed by its dinkiness. This anecdotal evidence doesn't really answer the question, though. 213.122.53.30 (talk) 18:13, 27 July 2009 (UTC)[reply]

Come to think of it, the lack of a horizon in puffin photos might be part of the problem. An image search produces lots of photos with blurry backgrounds, and any hint of a horizon is irregular and bumpy because that's the sort of place where puffins live. 213.122.53.30 (talk) 18:24, 27 July 2009 (UTC)[reply]

Name of tree?[edit]

What is the name of this tree? [1] I found lots of these [2] on the ground near it, what part of the tree was it? This tree is found in Auckland, New Zealand. thanks F (talk) 09:18, 26 July 2009 (UTC)[reply]

Liquidambar orientalis or Liquidambar styraciflua--Digrpat (talk) 13:21, 26 July 2009 (UTC)[reply]

thats a plane tree or plain tree (i dont know the spelling) but theres heaps of them in cambridge (new zealand)

Black Box[edit]

What are the components of a black box in the aeroplane??How is that it suffers very little damage and hence recovered fair enough???Also any idea of what kind of metal it is made up of??? —Preceding unsigned comment added by Gd iitm (talk • contribs) 14:46, 26 July 2009 (UTC)[reply]

Flight data recorders are located in the tail, so that the entire front of the aircraft will act as a “crush zone” that will reduce the shock that reaches the FDR. Modern FDRs are typically double wrapped in strong corrosion-resistant stainless steel or titanium. Red Act (talk) 14:59, 26 July 2009 (UTC)[reply]

IMHO, I don't think anyone other than Amelia Earhart ever referred to a Flight data recorder as an "FDR". (She was a big supporter of his, so that would explain it.) ;-) 98.234.126.251 (talk) 23:28, 26 July 2009 (UTC)[reply]

They are also (typically) bright orange spheres - the name "black box" is singularly inappropriate! The sphere is a stronger shape than a box - and orange is a more visible color than black in a burned out wreckage! Actually, these devices are quite often damaged in a crash - but they are designed in such a way that the recording can still be recovered even when the damage is pretty serious. SteveBaker (talk) 22:08, 26 July 2009 (UTC)[reply]

Commercial airliners normally carry a flight data recorder in the tail and a cockpit voice recorder near the front. These units are orange painted rectangular boxes, similar in format to other modular equipment that is made for easy replacement. SteveBaker's notion of spherical units seems far fetched, but no more so than this movie dialogue:

King Marchand: Stick around, I might want to play some golf.

'Squash' Bernstein: Boss, it's snowing outside!

King Marchand: We'll use red balls. Victor Victoria (1982) Cuddlyable3 (talk) 22:43, 26 July 2009 (UTC)[reply]

You can find a picture of a data recorder and a voice recorder here: NTSB.gov. — QuantumEleven 08:57, 27 July 2009 (UTC)[reply]

They are called "black boxes" because they are sealed off from the outside world, so are a Black box in a computing/electronics sense, not by colour. The article includes several photos of aircraft ones of various ages. -KoolerStill (talk) 16:22, 27 July 2009 (UTC)[reply]

Black boxes was a generic name for all aircraft Line-replaceable units which were all painted black. It is just that the voice recorder and data recorder became better known to the general public as (one of the) black boxes although they were not painted black like the rest. MilborneOne (talk) 16:41, 27 July 2009 (UTC)[reply]

Relative velocity[edit]

Suppose imagine that you are driving the car down a beautiful country side.The trees nearby i.e.on the the either side of the road appear to go pretty fast while the mountains atleast a mile away from the road appear to pass by pretty slow.It is a common observation.But relative velocity doesnt talk about distance anywhere.In common high school problems of calculating the relative velocity, it just says "put the negative of your velocity on the object of observation and you get the velocity at which the object(can be tree or mountain) APPEARS to pass." But the following technique doesnt work in my case why?? —Preceding unsigned comment added by 117.193.128.83 (talk) 16:39, 26 July 2009 (UTC)[reply]

You are describing parallax. What you observe isn't actually the trees or mountains moving, it's the angle to them changing. The angle is a function of both speed and distance. --Tango (talk) 16:44, 26 July 2009 (UTC)[reply]

Think in terms of angular speed, which is what the eye perceives. --Bowlhover (talk) 18:11, 26 July 2009 (UTC)[reply]

See also visual perspective. As you well know, this pencil has a constant diameter; but looking at it, it appears to get smaller in the distance. This is the same effect which makes the apparent motion speed seem slower for the distant mountains. Nimur (talk) 19:00, 26 July 2009 (UTC)[reply]

More specifically - the effect of perspective is that the apparent size of an object is proportional to one over the distance. What this means is that when you halve the distance between you and some distant object, the size doubles. When a tree is (say) 100 meters away, you only have to drive 50 meters to make it appear to double in size. When it's 50 meters away, you only have to drive 25 meters for it to double in size - so that nearby tree seems to grow FAST! However, if you're looking at a house that's 10km away - you have to drive 5km for it to double in size - which means that it takes a couple of minutes to double in size. For a mountain that's 50km away - it could take you 15 minutes to drive the 25km it takes to make it double in size. SteveBaker (talk) 22:03, 26 July 2009 (UTC)[reply]

I think I havent worded my question properly.I didnt mean to ask about the size of the object growing.I am sticking to the concept of relative velocity alone.I meant you are driving and to the left or right of the car ,the trees etc APPEAR( this has a unique meaning) to pass by and I DIDNT ask about approaching a tree and hence its size growing. (APPEARS in caps because...consider this---u are in space and u observe some stone approaching you.But there u dont really know whether you are approacing the stone or the stone is approaching you or both approaching each other.This is because you have no references at all in space unlike earth where you have the sky,winds etc as references) so just by going by relative velocity,I still havent got a satisfactory answer.I seriously doubt if it is connected to angular velocity.Nimur your answer does give me a vague idea but I am not very clear about your answer. 203.199.213.67 (talk) 04:30, 27 July 2009 (UTC)[reply]

Also the visual perspective website tells only about the smaller size of the distant objective but nothing about the relative velocity as asked by the person above.203.199.213.67 (talk) 04:33, 27 July 2009 (UTC)[reply]

Lets get one concept straight. Say you look sideways at a far off mountain while driving a car forward at 40Km/hr, the mountain does indeed go backwards at 40Km/hr, with respect to us. There's no doubt about that. But it appears to go much slower than that because of its distance. Your car window has a certain size, lets call it say one meter. Lets say your eye can see through the window, but only within certain angles - you can't look at something right behind you or right in front of you using this window, as you're not turning your head around. Lets say you can see only around 30° to either side of the center of your window. Now, the whole thing becomes much simpler and easier to understand. Say you spot a tree some 10m away. Now, complete the triangle of your line of sights on either side using the 10m as the altitude of your triangle. Using trigonometry, you can figure out the length of the base of the triangle, which is the distance for which the tree will be visible. This turns out to be 5sqrt(3) meters. So if you're going forward at 40Km/hr, the tree whizzes past in 0.78 seconds. But if the tree is replaced by a mountain 10Km away, the same base of the triangle, which is nothing but the distance for which you see the mountain, turns out to be a thousand times greater, which means it will take 778 seconds, or over 10 minutes to go past. So you see, as the others explained, its nothing but perspective, it looks as if it is going much slower, as we realize the change only in angle, not in distance. I hope I was clear enough to understand. Rkr1991 ^{(Wanna chat?)} 05:47, 27 July 2009 (UTC)[reply]

Suppose that while you're in your car, a nearby house and a distant mountain both take up 20 degrees of your field of view. Your car moves 20 m and you completely passes the house, but 20 m is nothing compared to the mountain, so the mountain seems to have barely moved.

The phenomenon you describe has everything to do with angular velocity. After all, the eye has no way of measuring actual velocity, so perceived speed corresponds to how quickly an object crosses your field of view (measured in degrees). If it zips by like nearby objects do, you think it's fast; if it takes ages to cross your field like a faraway house, you'd think it's slow. You might ask why evolution didn't wire the brain so that it can calculate actual speed from angular speed, but that's a question I'll have to leave for another ref desker. --Bowlhover (talk) 06:04, 27 July 2009 (UTC)[reply]

Because it can't be wired in! There's a shortage of input information, if the target is very far away. Even with stereo vision (two eyes), our depth estimation is still pretty poor (especially at far distances where the parallax of our eyes is negligible). To convert apparent angular motion into actual velocity, you also need a depth estimate. At close range (2 or 5 meters), we're pretty good at doing that. At long ranges (hundreds of meters and beyond), we're not getting actual depth information from our stereo vision (the parallax is beyond the range of our perception); we have to use other contextual clues to estimate depth, but these are unsuitably inaccurate. Nimur (talk) 15:37, 27 July 2009 (UTC)[reply]

My previous answer is still correct - but perhaps some more explanation is required. Our ability to perceive distance directly is by one of two mechanisms:

by using the amount of distortion in the lens of the eye required to get a sharp focus.
by using the amount by which our two eyes have to point inwards in order to form a single image. :The problem is that neither of those two techniques are sensitive enough to work beyond maybe 20 to 40 feet. Beyond that, we have to rely on the rate at which things change size as we move towards them (or they towards us). For very distant objects, (as I explained before) the size doesn't change rapidly enough for us to really notice that gradual increase - so it looks like far distant objects aren't moving at all...and we really can't tell how far away they are. For closer objects, the rate of size growth increases dramatically and it gets easier and easier to figure out how far away they are and how fast they are moving towards us (or us towards them). It really is all a matter of how the laws of perspective work. SteveBaker (talk) 18:24, 27 July 2009 (UTC)[reply]

If the nearby trees and the mountains a mile a way were really passing by, and you were standing still, the mountains would appear to move more slowly than the trees, because they are a mile away. Therefore they do indeed appear to pass at a speed equivalent to the negative of your velocity, when you are moving. That's what it would look like. 213.122.53.30 (talk) 19:02, 27 July 2009 (UTC)[reply]

Heh, I seem to have said that the mountains would appear to be moving more slowly than the trees, and also that they would both appear to be moving at the same speed. Oops. Both those things are true, though! Evidently "appear" has a flexible meaning. 213.122.53.30 (talk) 19:06, 27 July 2009 (UTC)[reply]

They do move at the same speed, but they don't appear to do so. That was the question. Rkr1991 ^{(Wanna chat?)} 10:06, 28 July 2009 (UTC)[reply]

Heart transplant: nerve connections[edit]

How does a transplanted heart connects to the brain?--Quest09 (talk) 19:49, 26 July 2009 (UTC)[reply]

Nerves severed in the tranplantation do grow back after a few years. However the patient does suffer from having no autonomic control prior to nerve regrowth, one of this is the increase firing rate of the SA node, with hemodynamic problems, hypertension, and arrhythmia also prevalent in postop patients. Sjschen (talk) 20:08, 26 July 2009 (UTC)[reply]

That means that the person won't need an artificial pacemaker? Can the new heart start firing by itself, perhaps after a small electrical shock?--Quest09 (talk) 15:53, 27 July 2009 (UTC)[reply]

Assuming nerve and muscle connections within the heart are all intact, the heart will beat spontaneously without external nerve connections. See Cardiac cycle#Regulation of the cardiac cycle. We don't have an article about suspended heart (or at least not a redirect to a related article), but one can remove a heart (I think it's most commonly done with frogs?), place it in an appropriate medium, plumb some vessels to it, and study the beating (and chemical effects on it) in vitro. DMacks (talk) 22:19, 27 July 2009 (UTC)[reply]

Elevator logic control[edit]

This question has been dual-posted at the Computer Desk, here. I am consolidating the answers from Science Desk to the post over there to avoid confusion and redundancy... Nimur (talk) 23:20, 26 July 2009 (UTC)[reply]