Wikipedia:Reference desk/Archives/Science/2009 August 9

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August 9

Is this guy a crank?

http://www.wholeapproach.com/index.php

I tried to google criticism of this website but no results. Any help?--12.48.220.130 (talk) 03:11, 9 August 2009 (UTC)

The evidence for these yeast syndromes is dubious at best, the condition is not widely accepted among the mainstream medical and scientific community. See [1] and [2] Rockpocket 03:55, 9 August 2009 (UTC)

While not specifically answering the question, Googling for criticism of a website is often ineffective because unless the person/website is a notable crank, it's likely no one has discussed it. Googling for the claims made or therapy or whatever is likely to be more effective presuming the person didn't come up with some 'novel' idea. Even better of course is to look into the science and website. Does the website mention any science to support it? Is there any science to support it? If for example, the website is describing some sort of treatment, then looking into the condition the treatement is alleged to help should be illuminating. Ultimately the best thing is perhaps not to ask is the person a crank but is there any evidence the person is not a crank? Nil Einne (talk) 17:01, 10 August 2009 (UTC)

Where can I find more about that? —Preceding unsigned comment added by 12.48.220.130 (talk) 04:35, 9 August 2009 (UTC)

See the references for Candidiasis#Alternative views. Red Act (talk) 10:12, 9 August 2009 (UTC)

Zero Velocity but accelerating!!!!!

Can an object moving with zero velocity have some acceleration?? --$\xi ri\pi i\vartheta \alpha \xi$ 04:17, 9 August 2009 (UTC)

Momentarily, yes. I suspect this is homework, so I won't give the detailed answer. However, watch the pendulum and you may be enlightened :) --Dr Dima (talk) 04:25, 9 August 2009 (UTC)

This is not homework. I just happened to ponder about it! I always get such stupid questions in my mind!!! --$\xi ri\pi i\vartheta \alpha \xi$ 04:34, 9 August 2009 (UTC)

Plot the trajectory of a ball thrown up into the air as a function of distance versus time. Take the derivative, to find velocity. Is the function defined at y=0? If so, then the object experienced zero velocity even undergoing constant gravitational acceleration. John Riemann Soong (talk) 06:00, 9 August 2009 (UTC)

Can an object be not moving and yet is accelerating at the same time? The answer is yes. But the "amount of time" the object spent at this strange state is infinitesimally small. 122.107.207.98 (talk) 11:39, 9 August 2009 (UTC)

Until you put it into a simple harmonic motion system that is. Well okay, it's still going to be infinitesimally small (thanks to the cardinality of the continuum), but it'll repeat that moment every time the cycle repeats. John Riemann Soong (talk) 14:11, 9 August 2009 (UTC)

The original questioner might want to contemplate the conceptual difference between velocity and instantaneous velocity. A particle can have an instantaneous velocity of 0, and a non-zero acceleration; but after an infinitely small instant of time, it will soon have a non-zero velocity as well. This thought-experiment is often used to introduce the concept of the derivative with respect to time, in an elementary mechanics or calculus class. Nimur (talk) 19:14, 9 August 2009 (UTC)

Bringing in the ideas that went into special relativity, a person sitting in a box that travel upwards at a constant acceleration, cannot distinguish this from sitting in a box at rest, in a gravitational field. (on the ground) This really goes back to Newton since the force the ground is pushing at you with is given as F = m*a where a is the gravitational acceleration. EverGreg (talk) 12:09, 10 August 2009 (UTC)

A train set out at midday, travelling (as they do) from A to B at 100mph. A common housefly sets out at the same time, travelling from B to A at 1mph. At point C, the fly hits the front of the train. In this instant, it is momentarily stationary. Since the fly and the train are both at point C - then either the fly's velocity changed from 1mph to -100mph in zero time (which would require an infinite acceleration and hence an infinite force) - or the fly slowed down, was briefly stationary, then gained a finite acceleration up to -100mph. In which case, was the train also stationary at some point? Did the fly stop the train? The problem with these thought-experiments is that they neglect the elasticity of objects at macro-scales and the sheer weirdness of things at the nano-scale. In theory, the fly reached zero velocity had an acceleration that was non-zero - but it can only have that for an amount of time equal to zero. In practice, time, position, momentum and force are all quantized in weird and wonderful ways - so that this issue simply doesn't come up as a practical problem. When the fly hit the train, both fly and train deformed, atom by atom - some atoms in the train did reverse direction briefly. The forces between the atoms acted to repel them from each other and cause a gradual slow-down, then acceleration of the two surfaces at the nano-scale. You really can't ask these questions at the 'macro' scale and get a sensible answer. SteveBaker (talk) 13:34, 10 August 2009 (UTC)

Certainly. Take a ball, hold it in your hand and then leave it - letting it free-fall. The moment you leave it, it has zero velocity ( wrt to you) but has an acceleration of g=9.8m/s/s/.

Velocity is always measured relative to a frame. Suppose you are running at a constant speed of 2m/s , another firend of your starts from rest, accelerating at .5m/s . At exactly 4 sec - he is at rest, having velocity of zero magnitude in your frame of reference. Hope this clears up things for you.

Dilip rajeev (talk) 07:31, 16 August 2009 (UTC)

Untitled Query

how to split hydrogen and nitrogen from urea. please say the method in detail. —Preceding unsigned comment added by Studiousvenkat (talk • contribs) 05:06, 9 August 2009 (UTC)

Welcome to the Wikipedia Reference Desk. Your question appears to be a homework question. I apologize if this is a misevaluation, but it is our policy here to not 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 how to solve such problems. Please attempt to solve the problem 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. Thank you. ~ Amory (user • talk • contribs) 06:12, 9 August 2009 (UTC)

Subscription required. If you can't access that article, then google "10.1039/b905974a" (that will bring up references to the paper). 152.16.59.102 (talk) 06:14, 9 August 2009 (UTC)

Uhh, how do you want your hydrogen and nitrogen? As ammonia? As N2 and H2? John Riemann Soong (talk) 06:18, 9 August 2009 (UTC)

Use a mass spectrometer - that will provide N , C, O and H atoms!83.100.250.79 (talk) 12:39, 9 August 2009 (UTC)

A related chemical process is the Haber process - an efficient method for producing ammonia, given nitrogen and hydrogen. The process is reversible, so under some conditions, you can produce nitrogen and hydrogen from ammonia. So, one method to solve the initial question is to decay the urea into ammonia (via hydrolysis) - and then use the ammonia into a reversed Haber process. You might also want to read about the urea cycle. Nimur (talk) 19:11, 9 August 2009 (UTC)

Suppose you're standing on the surface of a balloon

Further suppose that this balloon is in empty space, far away from any other matter, but you have your own air supply. Further suppose that this (very large) balloon is very elastic. Air is being pumped into it rapidly, and it is expanding. It has negligible mass (compared to, say, a planet), but because the surface is expanding, you are being accelerated.

Consequently (because your body has inertia), you are able to walk around on the surface. Because it's expanding at just the right rate, you feel a 'weight' just like you do when you walk around on the surface of the Earth.

Here's the question: how is this 'force' -- caused by expansion of the balloon -- fundamentally different (apart from its cause) from the force of gravity? Twang (talk) 08:25, 9 August 2009 (UTC)

Other than observing the relative motion of nearby objects (if any), I can think of no way to tell the difference, though the expansion would have to be in space rather than of space. Dbfirs 08:32, 9 August 2009 (UTC)

You wouldn’t be able to tell the difference, with local experiments. See Einstein equivalence principle. Red Act (talk) 10:26, 9 August 2009 (UTC)

A local experiment: Stop walking, stand and look at your feet gradually moving apart. Cuddlyable3 (talk) 12:31, 9 August 2009 (UTC)

"Local" is a technical term, it means (roughly speaking) that the experiment only concerns a single point (or an arbitrarily small region around that point). Your experiment isn't local since your feet are in two different places. --Tango (talk) 15:21, 9 August 2009 (UTC)

Wouldn't your acceleration be different depending on what sort of mass you had? What if you were as twice as heavy? John Riemann Soong (talk) 15:38, 9 August 2009 (UTC)

Yes, but if the pressure in the balloon was high enough you compressing the balloon would be a negligible factor. --Tango (talk) 15:52, 9 August 2009 (UTC)

I suppose it depends on how you define fundamentally, but the acceleration you'd feel on the balloon is essentially pressure, caused by the air being pumped in (work is being done). Gravity is gravity. ~ Amory (user • talk • contribs) 15:58, 9 August 2009 (UTC)

In science, things are only considered to be different if there is an experiment that tells them apart. According to General Relativity, there is no experiment that can tell acceleration (whatever the cause) and gravity apart, so they are the same thing. --Tango (talk) 16:03, 9 August 2009 (UTC)

This was meant as a response to Bus stop's removed comment, but it's applicable here. I was trying to imply that the fact that the two "forces" are from different causes matters here. I failed miserably. At any rate, the "weight" on the balloon is caused due to its expansion due to the pumping-in of air, as I said. What that means, however, is that more and more air must be pumped in in order to sustain that weight, as implied in the question. As the balloon expands further and further, you move farther and farther away from a given point, something you do not notice under the influence of gravity unless no other forces are in play. If you did the same thing with gravity (move away from the center of gravity), you would begin to weigh less and less as the distance between you increased. The question was about forces and weight, not accelerations, and our weight on Earth rarely involves a significant amount of acceleration. ~ Amory (user • talk • contribs) 16:36, 9 August 2009 (UTC)

I'm believe Amory has a point, but I disagree with the significance of the issue, or more properly, I feel that the response needs more qualification. With a very large balloon, on which the surface is approximately flat in a decent-sized neighbourhood of the observer, he needn't notice the change in its shape (which I'll add Amory very rightly did not mention), and let's suppose he build a house and other landmarks on this near-flat surface. How would he know he was moving? With reference to applicable landmarks, he wouldn't be. So he needn't notice.--Leon (talk) 16:46, 9 August 2009 (UTC)

Actually I think he would notice. While the shape doesn't noticeably change the size does. The radius of the balloon needs to increase with an acceleration of 9.8m/s². The distance between two points is the angle between them (in radians) multiplied by the radius, so that will be increasing at a speed equal to the speed the radius is enlarging multiplied by that angle. Assuming the balloon started at rest the size of the Earth and the most distant parts of the house were 20m apart, that corresponds to an angle of 20/6400000=1/320000 radians. The size of the house is then R/320000, where R=6400000+1/2*9.8*t². If we assume the house can survive an expansion of 1% before it collapses then it will collapse when (6400000+1/2*9.8*t²)/320000=20.2, ie. when 1/2*9.8*t²/320000=0.2, which is 3 hours and 38 minutes after the start. So this guy's house would collapse in less than 4 hours - he would notice that! It is only locally that acceleration and gravity are equivalent, a house is an extended object so it can tell the difference (at least, it can tell that the acceleration/gravity isn't uniform, you probably could describe the house collapsing in terms of tidal forces in some gravitational field). --Tango (talk) 17:22, 9 August 2009 (UTC)

That's true; though the larger the balloon's radius the longer the house would stand! However, more germanely, the environment would change globally, which makes creating some sort of "static" local environment difficult. I suppose that if the surface has zero friction, one could place some extremely large platform upon it to build such an environment. In which case I don't think he'd notice.--Leon (talk) 17:31, 9 August 2009 (UTC)

The larger the balloon's starting radius, the longer the house would stand. If I'd assumed the balloon had started at zero size and then the house was built once it reached the Earth's size, it wouldn't have lasted anywhere near as long (probably seconds, I haven't done the sums). I think if you had an enclosed platform that met the balloon tangentially (ie. at a single point - not possible in real life, but good enough for a thought experiment like this one), you wouldn't be able to tell the difference between that and a similar platform on Earth. --Tango (talk) 17:36, 9 August 2009 (UTC)

It’s possible to perform experiments that would distinguish between the two situations, even within an enclosed platform, if the distances and times involved in the experiment are too large for the experiment to qualify as being local, as is the case with the house example. Suppose that 20m wide house isn’t attached to the balloon, but instead is engineered to allow the balloon to expand under it. Suppose the house has a precisely flat, perfectly frictionless, 20m-long table in it, that’s been balanced with the use of a super-precise level placed at the center of the table. Take two perfectly frictionless objects, and place them so they’re precisely motionless at the ends of the table. Wait the 3 hours and 38 minutes. If the objects have moved together by about 1%, you’re on earth. If the objects are where you left them, your house is being pushed along by the expanding balloon. Or if you’re impatient, you can just weigh yourself with super-precise scales on the house’s ground floor, and in the house’s attic. If you weigh less in the attic, you’re on Earth. If you weigh the same in both places, you’re on the balloon. Red Act (talk) 20:00, 9 August 2009 (UTC)

You make a good point, I was so wrapped up in the details of the balloon I forgot the Earth's gravitational field wasn't uniform! --Tango (talk) 20:26, 9 August 2009 (UTC)

It's really worth noting that large spheres of gas have extremely appreciable gravity. In fact, most of the gravitating objects in our universe are large spheres of gas. How can the force of gravity be considered "negligible" if there is enough gas to make a balloon like the one that's being described? Nimur (talk) 22:01, 9 August 2009 (UTC)

Those large spheres of gas aren't made of gas as we know it. Most of Jupiter is metallic hydrogen. Stars are made of plasma and behave very differently to gasses like those in Earth's atmosphere. An Earth-sized balloon filled with Earth-like air would have a pretty low mass, even lower if you filled it with hydrogen instead. I'm not sure exactly what because I'm not sure how much it would compress under its own gravity. The density will also depend on the nature of the balloon itself. --Tango (talk) 22:14, 9 August 2009 (UTC)

Given the radius of Earth as 6371km, and a density of Hydrogen of 0.08988 g/L (massive underestimate), an Earth-sized ball of hydrogen would be approximately 10²⁰kg (if my quick math is right), a full 10,000 times less than the current Earth, but hardly negligible (compare to the mass of the Moon). ~ Amory (user • talk • contribs) 22:34, 9 August 2009 (UTC)

Where did that density come from? If that's under STP, it's pretty meaningless - why would this balloon be under STP? Don't forget you are further away from the centre of gravity than you would be on the moon, so surface gravity would be lower than you might expect. 10,000 times less density means 10,000 less surface gravity, so that's 0.00098m/s², only 100 times more than microgravity on the ISS [3] and that is often described as zero-g. It's pretty negligible, if you ask me. --Tango (talk) 22:52, 9 August 2009 (UTC)

If you're interested Tango (or others) I responded on my talk page here, not wanting to derail this (now lovingly answered) question further. ~ Amory (user • talk • contribs) 23:44, 9 August 2009 (UTC)

It's a thought exercise - the question is about the specific acceleration and forces on the balloon, trying to ignore all other influences. Clearly it's not realistic, but it's useful for our understanding to deconstruct a problem. ~ Amory (user • talk • contribs) 22:19, 9 August 2009 (UTC)

In response to an earlier objection that the expanding balloon would tear the house apart, there are casters and sliding pads which would allow the house to be supported at four or more points which would slip along the surface as the balloon expanded. The base of the house could also be a Teflon covered flat or curved plate or diaphragm which would slip nicely. Edison (talk) 02:48, 10 August 2009 (UTC)

We weren't trying to build a house, though, we were trying to hide the fact that the balloon was expanding. You could tell the balloon was expanding by watching the wheels turn around or whatever. --Tango (talk) 11:36, 10 August 2009 (UTC)

Couldn't you tell the difference with the Cavendish experiment? AlmostReadytoFly (talk) 11:48, 10 August 2009 (UTC)

So if you jump off of the surface of the balloon, there is nothing to reduce your outward velocity (no gravity) - but it seems like there is because the balloon is accelerating upwards towards you at exactly the rate that gravity would be lowing you down. However, there is an experiment you can do - which is to toss a ball vertically upwards at "escape velocity" for the planet you think you're standing on. If there is real gravity - then the ball will never return to you - if there is only this 'fake' gravity, then the ball will always come back eventually, no matter how fast you throw it. As others have pointed out, it's only the same as gravity "locally" - and as soon as you can do any kind of non-local experiment, you can tell the difference. You specified an otherwise empty universe - and that's just as well because otherwise we'd be able to measure the red-shift of nearby stars and discover that they too are accelerating towards us in a manner that could not happen if this were a gravitational field because they are too far away. The illusion of gravity is perfect for strictly 'local' observations...but is easily detectable with almost any kind of non-local experiment. The Cavendish experiment uses non-locality. SteveBaker (talk) 13:18, 10 August 2009 (UTC)

Actually, I don’t see how doing the Cavendish experiment would enable you to tell the difference. The Cavendish experiment doesn’t rely on non-locality at all. What the Cavendish experiment measured was the gravitational attraction between lead balls separated by a few centimeters, by measuring miniscule changes in the motion of a rod that only oscillated back and forth by about 4 mm. The distances involved are too small for variations in the Earth’s gravitational field to affect the measurements, and the masses of the balls are vastly too small for gravity’s nonlinearity to have a significant effect. So within experimental error, the Cavendish experiment would measure the gravitational attraction between the balls to be the same, whether you were on Earth or on the balloon. Red Act (talk) 15:19, 10 August 2009 (UTC)

Indeed. The Cavendish experiment is done horizontally so local gravity or vertical acceleration won't make any difference - that's really the whole point, you want to remove any contributions from anything other than the gravity of the balls. --Tango (talk) 15:30, 10 August 2009 (UTC)

Thanks, y'all. I hope you had as much fun with it as I did reading the replies. As a result, in time I may return with a more refined round 2 question. (Not that there's any comparison, but ... No damn wonder Niven took so long after Ringworld!!) Twang (talk) 04:22, 11 August 2009 (UTC)

I don't understand the 3-body problem

I tried looking at the article and I don't "get" it. Where can I have it explained in simpler terms?--12.48.220.130 (talk) 13:38, 9 August 2009 (UTC)

What don't you get? The idea is that we have 3 bodies (eg planets or something), and we also have their intial positions and speeds, as well as formula showing how they interact with each other (eg gravity in this case).

The problem is to find equations describing the positions of the bodies after time t.

The thing about it is that it's very difficult to solve...

You're probably familiar with simple 2 body problems such as the motion of a small ball under gravity (which is solved eaasily by assuming that the earth (that causes gravity) is so big that it doesn't move at all (an approximation) - the three body problem is to find the same sort of things for 3 things, with no approximations. (Probably you don't get a lot of the article because it's complicated maths - to be honest - neither do I)83.100.250.79 (talk) 15:15, 9 August 2009 (UTC)

I mean is it of the same nature as Fermat's last theorem or something?--12.48.220.130 (talk) 16:01, 9 August 2009 (UTC)

No. it's just a difficult set of equations to solve.83.100.250.79 (talk) 16:05, 9 August 2009 (UTC)

You should also read N-body_problem#King_Oscar_II_Prize_about_the_solution_for_the_n-body_problem which roughly says "stop asking stuff about things which you have no way of knowing if you've got the answer or not or fuck off" 83.100.250.79 (talk) 16:08, 9 August 2009 (UTC)

Try starting with something simpler first - do you get the 2-body problem?83.100.250.79 (talk) 16:43, 9 August 2009 (UTC)

Well yeah. That makes sense. So why can't three objects all revolve around the same barycenter as well?--12.48.220.130 (talk) 18:42, 9 August 2009 (UTC)

They can - but that's just one special case of a three body problem - one which happens to be much easier to solve. It's the general solution that is hard to get...83.100.250.79 (talk) 19:03, 9 August 2009 (UTC)

Well what's an example of a generic case that is hard to find a solution for?--12.48.220.130 (talk) 20:06, 9 August 2009 (UTC)

A mass 4 at (3,0,0) initial velocity (1,2,2)

B mass 10 at (3,4,3) initial velocity (0,-2,1)

C mass 3 at (-1,3,3) initial velocity (7,0,5)

All subject to gravitational type force (inverse square) eg kM₁M₂/r² (units in SI units or whatever)

What are the positions of A, B and C as a function of time?

(edited twice)83.100.250.79 (talk) 20:32, 9 August 2009 (UTC)

What makes generic examples as the one described above is the fact that the bodies will swarm around each other following open orbits (that do not repeat themselves) and will ocasionally suffer arbitrarilly close encounters. The closer the encounter the harder it becomes to predict what happens next due to Oberth effect which implies that an arbitrarily small imprecision in the orbits before the close encounter can turn into an arbitrarily large imprecision after it making the general problem impossible to handle. Dauto (talk) 21:04, 9 August 2009 (UTC)

The Oberth effect is only one of the many issues that plague a numerical solution to this problem. A naive iterative solution of the gravitational force equation, using Euler method iteration and incrementing the velocity and position of each body for each time step, is numerically unstable, and diverges due to accumulating error. For the non-technical reader: This is the simplest way you might think you can program a computer to solve the gravity equation - just solve for the force, update the acceleration, and update the velocity and position - but it doesn't work! This is the case even for the 2-body problem, which has an analytic solution. See "Inaccuracy and Instability of Euler's method" from the University of Buffalo's Math Department for a graphic visualization of numerical error on a very simple equation. Even some more advanced ordinary differential equation solvers tend towards numerical instability on the $1/(r^{2})$ force law iteration. This doesn't even consider whether the problem suffers from an analytic instability - this is strictly about propagation of error in the numerical differential equation solver. With an n-body problem, you have a large matrix of coupled differential equations, and you will find that the errors are not only propagating forward in time, but coupling in unusual ways throughout the problem. You certainly have to worry about this issue if you are solving the 3-body problem on a computer. Nimur (talk) 22:10, 9 August 2009 (UTC)

I remember for the intro programming class I took at school, one of the first things we did was program a solar system simulator that used Euler's method approximation. It generally worked alright if you didn't look too closely, but when objects got very close to each other, they would suddenly get flung off the screen at high speed never to be seen again. Rckrone (talk) 23:08, 9 August 2009 (UTC)

That's really at the heart of the problem. You can use numerical approaches to get an approximation to the correct answer - and you can make the time steps arbitarily small to get an arbitarily good answer - but the 3 body problem is chaotic in nature - small changes in the short term tend to blow up into arbitarily massive changes in the long term for all but the most stable cases. So you can't ever get a good answer over long time periods using a numerical method with finite precision. With the 2 body problem, the equations exist and can be solved for any arbitary time 't' and you can plug any 't' into the equation and get a good answer. I'm a computer game programmer - and for exactly these reasons, doing N body dynamics problems is one of the hardests parts of what we do. Even simulating something as seemingly simple as a pile of boxes sitting perfectly still on the ground becomes quite tricky in general-purpose dynamics software. If you naively plug in the math and naively simulate them numerically then they start jiggling, then bouncing - then they fly apart at crazy speeds...just like your solar system simulator! All sorts of cheats and kludges are required to make the 'real world' math function believably in a numerically simulated world. SteveBaker (talk) 13:05, 10 August 2009 (UTC)

A couple decades back I wrote a program to simulate a ship launched from Earth orbit towards the Moon's future position. It was designed so that the user had to find the right set of initial values to get the ship to orbit the Moon at least once. To make it as realistic as possible (but 'fly' in reasonable CPU time for that day), I consulted with a math prof and we came up with a Runga-Kutta 'solution' that could be quite accurate.
After toying with that for several months, I developed a MUCH deeper appreciation for any team that managed to get a real satellite into lunar orbit ... Twang (talk) 04:43, 11 August 2009 (UTC)

Yep - and that's not even a proper 3-body problem since the gravitational force exerted by the satellite onto the earth and moon is negligable. SteveBaker (talk) 13:03, 11 August 2009 (UTC)

Righto - I think I figured that if the 'restricted 3-body problem' was tough enough for Euler, it was tough enough for me ;-) (Some interesting background on how the old heavy-lifters got some work done anyway here. ) Twang (talk) 08:00, 12 August 2009 (UTC)

What is the name of this insect?

Does anyone know the name of this insect, photographed in South Germany? It must be approximately 2 cm long. Thanks a lot... --Edcolins (talk) 18:00, 9 August 2009 (UTC)

• 
  Unknown insect, first picture.
• 
  Unknown insect, second picture.

Nice photo, this site should be able to help you. [4]. 86.4.181.14 (talk) 21:32, 9 August 2009 (UTC)

Could it be a firefly/lightning bug? Firefly is found here. Bus stop (talk) 21:55, 9 August 2009 (UTC)

His name is Friedrich, and he would be happy to autograph your pictures. B00P (talk) 00:41, 10 August 2009 (UTC)

Actually it's his brother Willem, he parts his antennae the other way. 86.4.181.14 (talk) 06:16, 10 August 2009 (UTC)

Thanks for your answers... Could it be a female stictoleptura rubra (stictoleptura rubra) maybe? --Edcolins (talk) 18:42, 10 August 2009 (UTC)

What the heck is going on in this video?

http://strangepaths.com/canon-1-a-2/2009/01/18/en/

--12.48.220.130 (talk) 18:35, 9 August 2009 (UTC)

Crab canon. --Cookatoo.ergo.ZooM (talk) 18:56, 9 August 2009 (UTC)

Nothing much. The score sounds musical played from left to right as well as from right to left, and still sounds musical when both are played together. The mobius strip in the video is just a visualisation and (doesn't seem) to have anything particularily to do with it - the music could have been written on one side of a normal ring of paper and it still would have worked.

Was there something else mysterious.?83.100.250.79 (talk) 19:01, 9 August 2009 (UTC)

After edit conflict - The musical score is unfolded into a Moebius strip, which has unique mathematical properties. I'm pretty sure this is only a loose analogy to the musical score, though - notice that the note-bobs lose synchronization with the audio while traversing the score in Moebius strip format. Nimur (talk) 19:03, 9 August 2009 (UTC)

@83.100.250.79: It would NOT have worked, as the staff is "turned upside down" for the part of the table canon. --Cookatoo.ergo.ZooM (talk) 21:50, 9 August 2009 (UTC)

I didn't notice that.83.100.250.79 (talk) 22:57, 9 August 2009 (UTC)

Yes, it does work. You need to have the staff be upside down on the “back” side before doing the twist, in order to have it be right side up after the twist. To check that it works, try it by writing a line of text on a thin strip of paper, and turning it into a Moebius strip by following the video (I did). The sync is a little off when the Moebius strip is playing, in that the music starts about one whole note later than it should, but other than that, it’s accurate. If the sync looks way off for part of it, it’s because the music being played at that point is on the “back” of the strip at that point, not the “front” part that you can see. Notice that the “cursors” are solid on the side of the paper that’s being played at the moment, and have a gap on the “back” side of the paper, that isn’t being played. When following the cursors, it also helps to remember that the balls on the cursors are on the “up” side of the staff, when the cursor is viewed from the side of the paper that’s being played. Red Act (talk) 01:11, 10 August 2009 (UTC)

There's no good reason to put it on a Moebius strip or any sort of loop at all, since the piece doesn't loop. They play it through once in both directions at once and when they get to ends they stop. What makes the topology of a Moebuis strip or a regular loop interesting is what happens at the ends or when we go around in a full circle, but nothing like that is relevant here. Rckrone (talk) 01:36, 10 August 2009 (UTC)

Changes in DNA

Is an acquired mutation in the DNA still being instructed to create the mutated cells still controled at the mRNA level, telling the body that even though you were not born with certain gene mutation but it may have developed because of environment or lifestyle are those mutated cells controlled by the RNA still? —Preceding unsigned comment added by 71.155.212.203 (talk) 20:58, 9 August 2009 (UTC)

I can't make head or tail of your question. Why don't you try elaborating it a little bit more? Please do not refrain from using proper punctuation. Dauto (talk) 21:14, 9 August 2009 (UTC)

If there is a mutation in the DNA that someone is not born with, for example cancer cells that is not inherited rather is a result from environmental factors, are those cells still directed by the RNA telling or continuing to give the bad/mutated genes or cells and continue to make the mutated genes/cells (it doesn't come from few bad cell that breaks away to duplicate other cells)?

You still aren't making such sense. For example, what does "give the bad/mutated genes or cells" mean? However, the DNA replication process isn't likely to be affected by small mutations - the RNA, DNA polymerase, etc. will all do what they usually do. --Tango (talk) 22:19, 9 August 2009 (UTC)

Your question appears to violate universal grammar. I'll try to make some sense of it though. Cells with acquired mutations can purge them with DNA repair enzymes; I imagine DNA repair enzymes are located in protected regions of the genome in such a way that for those loci to acquire mutations would require some pretty massive damage (such massive damage would trigger apoptosis and kill the cell). However cancer cells probably arise where mutations knock out DNA repair enzymes, cell cycle control genes, etc. through the generations and it's done gradually enough that the cell doesn't go into apoptotic shock.

Are you asking whether damage to RNA post-transcription factors could lead to mutations? John Riemann Soong (talk) 13:36, 10 August 2009 (UTC)

This is my best guess at the parsing of the OPs two paragraphs:

"Is mutated DNA (which is still being instructed to create mutated cells) still controled at the mRNA level? Is mutated DNA still controlled by RNA?"

"If there is a new mutation in the DNA, for example in cancer cells, are those cells still directed by the RNA to make mutated genes or cells? Or do these new genes or cells come from a few bad cells that break away to duplicate other cells?" 89.240.199.45 (talk) 13:57, 11 August 2009 (UTC)

Attachment for cooling cars pre-ac?

I was at a classic car show and saw an attachment on the window of a Nash Rambler. The owner said it was for cooling the passenger compartment when traversing the desert in the Southwest US. Drivers would rent the device at one end, which would be filled with ice and attached to the window. At the other end of the journey, the device was then refilled with ice and rented to another driver going the opposite direction. What is the actual name of this attachment, and where can I find more details? DarkAudit (talk) 22:59, 9 August 2009 (UTC)

Car cooler. -96.255.161.148 (talk) 01:48, 10 August 2009 (UTC)

That's it. Thanks!. DarkAudit (talk) 01:57, 10 August 2009 (UTC)

I love this place!!!!! Especially the comedy double acts!!!!! 06:14, 10 August 2009 (UTC) —Preceding unsigned comment added by 86.4.181.14 (talk)