Wikipedia:Reference desk/Archives/Science/2007 October 7

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[edit] October 7

[edit] exceed the speed of light

if a rod made of unyielding material was attached to a motor perpendicular to its rotation and the speed of the motor could be increased to its maximum for example 10,000 rpm. how long would the rod need to be before the ends would exceed the speed of light? how could it be mesured ? and what would be the effect on the ends of the rod. if a message were attached to one end of the rod and two points along the circumference point A and B were monitered would the message leave A and arrive at B faster than the speed of light? please excuse my spelling and gramer. —Preceding unsigned comment added by 68.253.205.219 (talk) 01:03, 7 October 2007 (UTC)

they wouldnt exceed the speed of light. you cant make anything go faster than the speed of light. —Preceding unsigned comment added by 68.190.122.72 (talk) 03:06, 7 October 2007 (UTC)

  • Agreed. Faster-than-light travel may well be possible, but it would involve breakthroughs that would change our fundamental understanding of physics, not something rinky-dink like a motor. Also, for what it's worth, it would also violate known physics to make an "unyielding material. --M@rēino 03:44, 7 October 2007 (UTC)
The flawed assumption is in the "unyielding material." It is not practical to build such a rigid structure. Our theoretical understanding of materials suggests it is not even theoretically possible to have a non-rigidrigid body over such distances. The only way the "other end" moves is when the atoms interact with each other through the material; that interaction can't happen faster than light. Nimur 03:58, 7 October 2007 (UTC)
...of course you mean not even theoretically possible to have a rigid body over such distances, right? —Keenan Pepper 04:35, 7 October 2007 (UTC)
Thanks for correcting my error! Nimur 04:52, 7 October 2007 (UTC)
Be careful with the rote "nothing faster than light" response. Angular velocities can and often do exceed the speed of light. Imagine a pair of scissors and measure the point at which the blades meet. Close the scissors and that point moves from the handle to the tip. It's an angular velocity and can be much faster than light. The key is that no information is gained faster than light. --DHeyward 05:10, 7 October 2007 (UTC)
And since someone usually brings it up whenever "faster than light" questions are asked, it may as well be me: Cerenkov radiation. GeeJo (t)⁄(c) • 10:35, 7 October 2007 (UTC)

Nimur is correct. Any such rod would invariably bend as you attempted to rotate it; perfect rigidity would require a form of matter unknown to our current laws of physics. Someguy1221 05:20, 7 October 2007 (UTC)

Additionally, as the tip of the rod would approach the speed of light (c), its apparent mass would increase, approaching infinity as the speed approaches c, requiring infinite energy for reaching c. Icek 09:57, 7 October 2007 (UTC)

Obviously no real material could withstand such high stress, but nothing in special relativity precludes the existence of a rigidly rotating rod as long as no part of it is moving at c or faster. The formula for the speed at the tip is the same as the Newtonian formula: ω times r. In this case the maximum rod length is 2c / ((10000 rpm) (2π radians/rotation)) = 570 km.

Regarding your second question, the coordinate time for light to travel from one end of the rod to the other should be, in the limit, \int_{-\frac{c}{\omega}}^{\frac{c}{\omega}}\frac{dr}{\sqrt{c^2-\omega^2r^2}} = \frac{\pi}{\omega}. This is finite, and the effective time dilation factor at the edges goes to zero in the limit, so in this (totally unrealistic) limiting case, the two ends of the rod will be able to communicate effectively instantaneously from the perspective of their own proper time. This is a good illustration of the fact that the constant-speed-of-light rule only applies to inertial frames. -- BenRG 11:35, 7 October 2007 (UTC)

The key to this is that as far as the engine is concerned, the tip of the rod is moving at relativistic speeds - so the mass of the rod will start to increase as the engine speeds up. The amount of power the engine has to produce to keep the rod spinning increases greatly. Unless the engine is capable of producing an infinite amount of energy, it will never manage to make the rod spin at the speed of light. So there is no weirdness here - nothing gets up to the speed of light. SteveBaker 14:52, 7 October 2007 (UTC)
Only the part of the rod moving exactly the speed of light requires infinite energy. Since this part is infinitely thin, I don't know how that works. Getting anything to exceed the speed of light, however, requires a complex amount of energy. — Daniel 15:25, 7 October 2007 (UTC)
Indeed - it's irrelevent that it's infinitely thin - the fact is that if any part of the rod comes anywhere close to the speed of light, the mass increases spectacularly - as does the power required from the motor. There is absolutely no way to even get as high as the speed of light along any part of the rod - so what happens at the speed of light (or beyond) is irrelevent. You can't get there - so the question simply doesn't arise. SteveBaker 23:00, 7 October 2007 (UTC)
For a rod of uniform density, the average gamma factor at the limiting speed is \frac{\omega}{2c}\int_{-\frac{c}{\omega}}^{\frac{c}{\omega}}\frac{dr}{\sqrt{1-\omega^2r^2/c^2}} = \frac{\pi}{2}. So indeed it takes only finite energy to spin the rod up to this theoretical maximum: \left(\frac{\pi}{2}-1\right)mc^2, or around 14 billion kilowatt hours per kilogram. Could be worse. This ignores the tension in the rod, which also has mass, and it ignores the fact that any real substance would break long before this point. It's also worth pointing out that the rod will not bend, no matter how fast it's spinning, as long as the angular velocity is constant. The ends will lag behind the center as it's being spun up, but once the torque is removed the equilibrium motion is PT invariant, and by symmetry the rod must point radially outward. -- BenRG 19:24, 7 October 2007 (UTC)
Why are you even trying to calculate an average gamma? (Not that your equation is correct - it's not) That's all utterly irrelevent. The energy to get the very tip of the rod up to the speed of light is infinite - the rest of the rod is essentially irrelevent. SteveBaker 23:00, 7 October 2007 (UTC)
The gamma of the very tip of the rod is infinite, but the mass of the very tip of the rod is zero. My integrand goes to infinity at the integration boundaries, but the area under the curve is still finite. That's just the way it is sometimes. Keep in mind that this is a limit. We're not talking about the behavior at the limit point, but the behavior as you approach it. So the energy is certainly finite; the question is whether it grows without bound. Maybe you're saying that real matter isn't continuous and there has to be an outermost atom. It's unclear to me how to deal with real atoms in this kind of situation -- I think inevitably you're going to be forced to acknowledge other effects that will doom the rod way before we get to this limit. For an idealized material with the mass concentrated at finitely many classical points, you basically get a Riemann-sum approximation to the integral. Or maybe you're saying that the energy must be infinite because otherwise we're claiming that you can accelerate the tip past the speed of light with finite energy. If so, there's nothing to worry about. If you pump more than the maximum energy into the (idealized, continuous) rod, it won't go faster than light, it'll just break. There's a similar limiting result for linear acceleration. If you pull on a rod of length d with an acceleration of more than c2/d, it has to break for purely relativistic reasons. -- BenRG 11:29, 8 October 2007 (UTC)

[edit] Brain damage in new borns

I am trying to find answers on new born brain damage that causes the inability to suck, swallow, cry or know hunger pains. I am doing a paper on this in the name of my son who died from this 4 months after he was born. It is for a psychology report.


Thank you,

darlene Langford —Preceding unsigned comment added by 98.192.21.181 (talk) 01:47, 7 October 2007 (UTC)


Hypotonia is a classic cause of the symptoms you describe. Hypotonia is also a sympton/early indicator of other neurological problems.. --DHeyward 05:14, 7 October 2007 (UTC)

[edit] Science - Movement Receptors

How do the Movement Receptors receive a sensation of movement when they are well below the surface of the skin —Preceding unsigned comment added by 124.184.77.182 (talk) 04:17, 7 October 2007 (UTC)

That's where movement happens: inside, not on the skin. Proprioception uses proprioceptors within the muscles to give feedback about position and movement. - Nunh-huh 05:19, 7 October 2007 (UTC)
I wonder if the question was really about Semicircular canals. --JWSchmidt 20:49, 7 October 2007 (UTC)

[edit] Mosquito bites

Are there any topical creams, chemicals, or other remedies known or claimed to be effective at reducing the severity of a mosquito bite if applied immediately after being bitten? A mild peroxide solution occured to me, but unfortunately I couldn't find much on Wikipedia about this. Someguy1221 06:25, 7 October 2007 (UTC)

I've heard vinegar helps. Why peroxide? DirkvdM 07:56, 7 October 2007 (UTC)
Because ER said it could be used to destroy viruses :-) Oh yes, I know a good source of information when I see one...(not that I think mosquito bites have anything to do with viruses, but the ability to destroy a virus would likely imply the ability to disrupt proteins, blah blah, etc.) Someguy1221 08:07, 7 October 2007 (UTC)
In the United States the FDA recognizes ammonia as effective in reducing the symptoms of insect bites and stings (including mosquito bites): [1]. A number of over-the-counter products contain ammonia. After Bite is probably the largest name; it contains a 3.5% solution of ammonia in a pen-shaped applicator with a sponge tip. The link I provided also has a list of other products that can ease itching and inflammation post-bite. TenOfAllTrades(talk) 15:03, 7 October 2007 (UTC)
Topical steroid cortisone cream (containing 1% hydrocortisone) is very effective in reducing itching. This is readily available over the counter, and because it is applied topically, it does not have the bad side effects of taking steroids internally. I have found it useful in reducing the itching from mosquito bites applied at any time and renewed a few times a day.--Eriastrum 16:55, 7 October 2007 (UTC)
Betnovate(-n?) is one I've also had experience with. It's also useful for minor burns, particilar if applied immedietly after you've stopped running water over the burn. Nil Einne 13:14, 9 October 2007 (UTC)

[edit] Through the woodchipper

Fatality Assessment and Control Evaluation If you've got a good imagination, these reports can be scarier than any ghost story. Here are three poor people who found themselves inside working woodchippers, and what I am wondering about is why only one of them went all the way through. "The victim's remains were recovered by police forensic detectives and transported from the site." Implies that this poor guy went through, plus the account says the chipper was still running. I imagine an idling woodchipper, a really gruesome mess, and maybe an odor of blood.

Then there's the sad story of a 14 year old "The chipper drum jammed and came to a stop after the victim's torso had been fed into the machine." Meaning this chipper couldn't seem to work him all the way through. The same thing happened to another 28 year old: "When the climber approached the chipper with a load of branches, he noticed the victim’s legs sticking out of the chipper’s feed chute. He ran to the rear of the residence and notified the foreman."(Part of me wonders why anyone needs to be told to shut off the machine in that situation without the forman's say so, the rest of me thinks I don't know what I'd do if I saw that happening to a co-worker)

So I'm wondering if maybe the chipper in the first story was maybe bigger than the latter two? (Because I would have thought a machine which could chip 4-5 inch thick branches wouldn't have that much trouble with tissue and bone, but evidently that's not always so given the second and third cases.) Anynobody 01:59, 8 October 2007 (UTC)

[edit] Cerebellum and neural pathways

On this site (in a square to the left) it says: "The cerebellum's anatomical location helps us to better understand its functions. It lies parallel to two main neural pathways: one that carries sensory messages to the part of the brain that analyzes them, and another that emerges from the cortex and descends to the muscles to make them contract." Would anybody know exactly which two neural pathways are meant? Lova Falk 12:32, 7 October 2007 (UTC)

I'm not sure what it means for the cerebellum to "lie parallel" to a neural pathway. But if I had to take a guess: 1) the sensory -> brain pathways are the dorsal column-medial lemniscus system, which is one pathway by which sensory information reaches the brain; 2) the brain -> muscle pathway is the corticospinal tract (and probably the rubrospinal tract), which controls muscle movement indirectly via the spinal cord. The analogous cerebellar pathways are 1) the spinocerebellar tracts and 2) the cerebellocortical tracts. See Cerebellum#Peduncles for more on the input/output tracts of the cerebellum. --David Iberri (talk) 14:04, 7 October 2007 (UTC)
Thank you for your help! Lova Falk 17:20, 8 October 2007 (UTC)

[edit] chemicals

which is king of all chemicals? —Preceding unsigned comment added by 61.2.48.232 (talk) 14:51, 7 October 2007 (UTC)

Chemical King? - hydnjo talk 15:14, 7 October 2007 (UTC)
According to Google, it's sulphuric acid. Or maybe mustard gas. Algebraist 16:55, 7 October 2007 (UTC)
Water. SteveBaker 22:52, 7 October 2007 (UTC)
Steven's wrong, you want dihydrogen monoxide. Someguy1221 22:59, 7 October 2007 (UTC)
But then my bottle of says it's "100% pure spring water with no chemicals" :p --antilivedT | C | G 03:02, 8 October 2007 (UTC)
I always find those labels hilarious. My family lived in Malvern (famous for its water) for a long while, and you used to see groups of people along the roads in the Malvern Hills stopping and getting water from the springs, while only a few yards away was a flock of sheep defaecating/urinating on the grass, or dogwalkers letting their animals "do their business" slightly farther uphill. Nobody even looked up or thought twice. GeeJo (t)⁄(c) • 12:03, 8 October 2007 (UTC)
It's OK, dog poop is one of those "All Natural Ingredients" that we hear so much about. There probably aren't any chemicals in it, either. :-) SteveBaker 13:48, 8 October 2007 (UTC)
Pfft most people feed their pets junk most of which isn't organic. If a farm animal fed non-organic feed isn't organic and therefore not all natural (according to people who use such terms) then a dog not feed an all organic diet is surely not organic nor is their poop. Actually this gets me wondering, is cow dung from a non-organic cow used on organic farms? Is it okay if used as fertaliser provided not directly consumed? Nil Einne 13:08, 9 October 2007 (UTC)
There are the noble gases or maybe titanium from the titans, unfortunately caesium is not named after caesar, also aqua regia is probably your best bet —Preceding unsigned comment added by 87.102.17.101 (talk) 13:00, 8 October 2007 (UTC)
Tetraneutron? Chemical Ali? Elvis? (he was the king and he liked chemicals) Nil Einne 13:08, 9 October 2007 (UTC)

[edit] Common wildflower ID

I know this is a common wildflower but I can not find an online classification table of flowers that will ask me the value of various characteristics for the purpose of identification. What is the name of this wildflower and is there a way to identify it online by entering the values of its various characteristics? Clem 19:19, 7 October 2007 (UTC)

It looks like Lantana camara, but I doubt it is a "wildflower." Plants can be identified using "keys" that consist of a series of choices that will eventually lead you to the correct identification. However, to use them they require technical botanical knowledge that makes them inaccessible to most people.--Eriastrum 20:31, 7 October 2007 (UTC)
You are joking, right? Keys that require secret "...technical biological knowledge that makes them inaccessible to most people..." versus keys such as color, dimensions, etc. and other very common or easily explainable or discernible attributes? —Preceding unsigned comment added by Kadiddlehopper (talk • contribs) 14:02, 9 October 2007 (UTC)
No, I'm not joking. Plants are identified by details of flower and seed structure for the most part. Using superficial details like shape of leaves, color of flowers, etc. is seldom of much use outside of a restricted geographic area. In order to describe these (usually tiny structures needing a hand lens), botanists have developed their own specialized vocabulary: corolla, stamen, zygomorphic, hirsute, alternate leaves, and on and on. However, these terms are not in any way "secret"! Any introductory botany course at the college level will teach you these terms and how to use keys. To identify flowers without this kind of knowledge, there are usually local popular books that have photographs of the commonest plants in a particular region. Using these photos, you simply go through until you get a match. There are many on-line sites that offer such information. For example, for Florida there is a good site flwildflowers.com with a gallery of photos of some common wildflowers, including Lantana camara. You don't indicate where you are located, but I suspect that it might be Florida or somewhere in the SE United States. Another problem is that there are many species of plants in a particular area--hundreds or even thousands, and many of these are very similar. It is perfectly possible, for example, to learn all the species of birds in a particular area, but not so easy to learn all the plants.--Eriastrum 15:25, 9 October 2007 (UTC)
Perhaps you are not aware of what modern technology and modern classification methods have brought to the table in regard to quick and accurate lay identification capability. For instance, you mentioned geographic area. Geographic area is now a matter, for the purpose of classification and of identification, of using GPS. If location can eliminate the vast majority of species (80%) with similar characteristics then colors well beyond the capability of the human eye are available for the purpose of classification using basic digital camera technology which can eliminate say another 10%, thus leaving only 10% (80%+10%) yet uneliminated. While a plant may have special scientific attributes beyond location and color, it may have other attributes open to modern technology, which can be utilized for the purpose of lay classification. In fact, should biologists fail to acknowledge and incorporate now common and growing technological capability, they and their otherwise detailed expert knowledge may be displaced by new databases and classification methods, vastly superior for the purpose of quick and accurate identification by the laymen, to their own. Clem 10:54, 10 October 2007 (UTC)

What you suggest is certainly possible. Has anyone done it yet? I don't know. However, the general trend in the classification of organisms is toward cladistics, which depends upon the genome (the genotype), and not the appearance (the phenotype). The purpose of such classifications goes far beyond mere identification--ideally it is a repository of evolutionary information--a detailed family tree, so to speak. See our articles alpha taxonomy and systematics. The sort of classification/identification database that you describe would have to be entirely artificial and for practical identification uses only. As such, there might be relatively little motivation for a scientist to compile it.--Eriastrum 16:23, 10 October 2007 (UTC)

Very true and not necessarily intended, in fact the opposite, for scientific use. Consider Flickr and Youtube databases though, that even the Wikipedia now taps. Still technology may ideally one day put real time genome classification/identification capability in the hands of the laymen, a day I certainly look forward to. Imagine living in a world where no living thing can escape identification simply because there is not a scientist around. Clem 18:09, 10 October 2007 (UTC)

[edit] Speeds of Jaguars

What is the average speed of a jaguar, meaning the cat?

I couldn't find a number anywhere online. But they are 'ambush predators' - so they have no need for great speed. I doubt they are particularly fast. SteveBaker 22:49, 7 October 2007 (UTC)
Might you mean cheetahs? The article says they can reach speeds up to 110 km/h. DirkvdM 06:32, 8 October 2007 (UTC)
No! Cheetah's are ridiculously fast animals - but they are smaller, lighter and live on the wide open plains of Africa. Jaguars live in South America - in the rainforest - where there isn't really room to get up to speed. They hunt by pouncing on things from trees or the undergrowth - so they really don't need to be able to run particularly fast. SteveBaker 13:22, 8 October 2007 (UTC)
I meant the original question might be about cheetahs because they are so well known for their speed. DirkvdM 17:58, 8 October 2007 (UTC)
This page, reports they can run up to 70 miles per hour. I'm not sure about the accuracy of the number, as it doesn't list a source to be checked. Wikipedia now has me checking for Reliable Sources even on non-WP websites. 152.16.59.190 06:36, 8 October 2007 (UTC)
I definitely don't trust that page. At the bottom, it says "This page was created by Eleva-Strum sixth grade students" - do YOU trust 6th graders to do top-notch research? I'd be very surprised indeed if a Jaguar could run faster than 30mph. SteveBaker 13:22, 8 October 2007 (UTC)

[edit] important people in biological sciences

Hello,

I am preparing to take my exams for my Master's in Biology, and need to know if there are any important historical or current scientists that I may have missed while studying. I'm interested in people who have made a very significant contribution to biology- big whigs like Darwin, Gould, etc. Can you help? —Preceding unsigned comment added by 68.90.137.230 (talk) 22:25, 7 October 2007 (UTC)

Oh, but there are so many. If you're up for a good read, try starting at History of biology. Someguy1221 22:32, 7 October 2007 (UTC)
Right. The history of biology is a rich and diverse field of study in its own right. There's no easy answer to your question because it's not clear why you want to know these things, unless history is a large component of your master's exams.
In any case, if I were going to pick a dozen of people (omitting Darwin and Gould) who are routinely cited as extremely important to the history of biology, the list might look like (in order of appearance):
  1. Aristotle
  2. Antonie van Leeuwenhoek
  3. Carolus Linnaeus
  4. Buffon
  5. Antoine Lavoisier
  6. Alexander von Humboldt
  7. Gregor Mendel
  8. Francis Galton
  9. Louis Pasteur
  10. Thomas Hunt Morgan & the other Drosophilists
  11. R.A. Fisher, Ernst Mayr, & the other modern evolutionary synthesis bunch
  12. James Watson
  13. Francis Crick
Now this is a sorely incomplete list but going over it would give you a brief history of some of the major figures in the history of biology, as seen from the vantagepoint of the present (which is not necessarily what interests historians) and with a heavy bent towards heredity. Now this may not have any relevance at all to your master's exam, I'm afraid. --24.147.86.187 21:25, 8 October 2007 (UTC)

[edit] Personality Disorders

Is it possible to have both Borderline Personality Disorder and Histrionic Personality Disorder?

  • I've linked the 2 terms for convenience. Exxolon 23:53, 7 October 2007 (UTC)

75.182.70.75 23:50, 7 October 2007 (UTC)

Can't see why not.87.102.17.101 14:01, 8 October 2007 (UTC)
Is this a joke? the term "suicide bitch" seems applicable here87.102.17.101 14:02, 8 October 2007 (UTC)

[edit] Excess of Speed of Light

I know that man has the idea that the speed of light is the fastest method of traveling, but I'm certain there is a much faster method. The method I'm pondering is traveling at the speed of thought. This method involves almost to time element, and dwafts the speed of light. Is there a method/way to travel at the speed of thought? —Preceding unsigned comment added by Robert Lucero (talk • contribs) 23:55, 7 October 2007 (UTC)

There is no such thing. Thinking is a chemical process of the brain, and has nothing to do with velocity. -- Kesh 00:21, 8 October 2007 (UTC)
The speed of thought, if you mean the speed at which someone thinks, is much, much slower than the speed of light. Consider how long it takes for the brain to process basic physical stimulus—reaction time, or mental chronometry—which is palpable by simple observation (in the millisecond range), unlike the speed of light, which for human purposes along local distances has the apperance of being instantaneous. --00:34, 8 October 2007 (UTC) —Preceding unsigned comment added by 24.147.86.187 (talk)
If some people think they can travel to another planet faster than light, then maybe they are on another planet already. —Preceding unsigned comment added by 88.109.198.32 (talk) 02:58, 8 October 2007 (UTC)
In a science fiction story by E. E. Smith a method is found by which space ships can travel at the "speed of thought" and in the story the "speed of thought" is imagined to be much faster than the speed of light.....a real time saver for plots involving inter-galactic travel!.--JWSchmidt 03:26, 8 October 2007 (UTC)
The entire Dune series uses thought based navigation that is faster than light. They use drugs. Probably the only way to make it work. --DHeyward 07:02, 8 October 2007 (UTC)
It's all very well for you to just randomly 'hope' or 'imagine' that man can travel faster than light - but the reality is that physics simply doesn't allow you to do that - the laws of relativity guarantee that nothing that has mass can travel at the speed of light or beyond. As for 'the speed of thought' - quite honestly that's just bullshit. It's a cutely touchy-feely concept - but in reality, brains are S-L-O-W. Light can cross the width of your head in well under a nanosecond. There is no possible way for you to think anything in a nanosecond. A single nerve cell takes a couple of milliseconds to do anything. In the time just one brain cell takes to do something, a beam of light has travelled about a million feet. Then, light is zipping along at 300 million meters per second - but your nerve impulses travel at a leisurely 10 to 100 meters per second. Heck we have cars that can go faster than "the speed of thought". 100m/s is 223mph - so the Bugatti Veyron can already drive faster than the speed of thought. The speed of light is at least 3 million times faster - without even considering the time the neuron takes to fire! Please - don't just dream up crap like this. Do some basic research before you come up with theories that just sound cute but which have absolutely no basis in...in...anything, actually! SteveBaker 13:16, 8 October 2007 (UTC)
It sounds like you think that the speed of light is just the fastest speed that anyone has come up with a way of travelling at. In fact the speed of light is the absolute maximum speed at which any information or objects can travel (there is an article on Introduction to special relativity if you are interested). The speed of thought - if it were to be defined in any sensible way - could not be faster than light. If it really depresses you to think that nobody is ever going to realistically be able to leave the solar system, you might want to read Wormhole and Twins paradox, which give at least a little bit of hope. Tachyon may also be of interest. Bistromathic 20:42, 8 October 2007 (UTC)

You guys are putting together alot of scientific thoughts, but let me help you. The answer lies in "Pure Matter." Nothing in this world is pure. What is pure matter? Do you know? In this world of course we can't travel faster than light, but how about another dimension? How many dimensions are there? Three, four or five? And if there are more dimensions, how do we get there? Now put some scientific thought into this.

Don't limit your thoughts. The speed of thought I am refering to is this: If I want to travel to Mars I am there in the same amount of time it takes me to travel to the Moon, but Mars is to much farther away. Where is the time element?

Can you figure this out?


Thanks