Science desk | ||
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< January 13 | << Dec | January | Feb >> | January 15 > |
Welcome to the Wikipedia Science Reference Desk Archives |
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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. |
My reading suggests that after an egg is fertilized in vivo, it is composed of stem cells that continue to divide at least until the egg attaches to the uterine wall. The write up under stem cells says "When given no stimuli for differentiation, ES cells will continue to divide in vitro and each daughter cell will remain pluripotent." The specific question is: Is this also true in vivo and what is the stimuli in vivo that begins the differentiation? The answer I am expecting is that it is something in the process that is initiated following attachment of the egg to the uterus that begins the next stage of embryonic development and if the egg does not attach, it degenerates and gets flushed with the next menstrual cycle.-- Billxm 00:23, 14 January 2007 (UTC)
I want to construct this model gun from sheet metal for laser-tagging purposes. Given that the diameter varies along the length of the gun, how might I accurately fold the metal? And ideas for making the gun handle, which I'd like to construct from the same metal? The blue part is a plastic window. >> gun<< -- Username132 ( talk) 00:23, 14 January 2007 (UTC)
If you use very thing sheet metal, you could maybe stretch it around a mold to get the desired shape. A ductile metal like copper would work best. If it's too thick to stretch, you may have to create a cylinder for the middle and two cones at the ends, to approximate the barrel shape. StuRat 04:29, 15 January 2007 (UTC)
I am doing a science fair project related to light pollution. I plan to zoom in on 'earth at night' maps located on the Internet and count the number of pixels in a certain 'area' (e.g. mid sized city) and see if light pollution naturally occurs in areas where there is population. Unfortunately, few (or no) maps on the Internet are reliable enough for me to look at (because of low res, no state or country boundaries, chance of being Photoshopped to make the image look 'better', etc...) and the process seems too tedious (city boundaries hard to 'distinguish', time in counting pixels, etc...). Can anyone help me, like introduced me to some special software or a good image (ahem...I mean really good, and better than the IDA stuff or the World Atlas of Night Brightness)? And if you can find the latter (an image) please give me a suggestion on how I can make the project less tedious. If you think I should have a new project, please keep it so I don't have to go outside during the nighttime or have to buy too many things. Thank you! —The preceding unsigned comment was added by Member ( talk • contribs).
Here's a nice map of the US with states shown: [2]. You can look at a political map for each state and figure out what each city is. StuRat 04:10, 15 January 2007 (UTC)
If I have a bottle of ice and water and want to drink the water -- will it help if I violently shake the bottle and splash the ice/water around?
I'm 14 years old but I seem to have hearing problems. I've always had the problem of hearing people talk, but never understanding what they are saying, especially when there is background noise or I am talking on the phone. This is obviously annoying because I either say what 5 times before understanding, or I just nod and say yes, not ever knowing what they just said. I also just listened to these high frequency " mosquito noises" on this website [4]. A teenager like me is supposed to be able to hear from 21.1 khz to 22.4 khz. I can only hear up to 14.9 khz, which is what people 39 and under are supposed to hear! I have never listened to music on earphones very loud for long periods of time and I don't go to loud concerts. However, I did have many ear infections and had to have ear tubes put in when I was young. Is my problem just going to get worse as as I get older? Maybe as far as though I will go deaf? Hopefully this doesn't count as medical advice. Thanks for your responses. :-). Imaninjapirate talk to me 02:05, 14 January 2007 (UTC)
Stop! Don't panic! Never use the computer to diagnose yourself or others. You didn't go into detail about how you listened to the tones. Unless you have a fantastic computer/audio system, you can't reliably test your hearing. The high frequencies won't get through most speakers. There's a good chance that you don't have a problem, but the only way to make sure is to have your hearing tested by a professional. Bunthorne 06:31, 14 January 2007 (UTC)
The two possibilities that come to mind to describe being able to hear but not able to distinguish words are:
1) Lack of high frequency hearing, as you suggested may be the problem in your case. I suggest having your hearing tested, and possibly using hearing aides. They can be small enough to hide within the ear canal, and can selectively amplify certain frequencies. Parabolic microphones also allow you to hear voices from one direction only, but those are, of course, highly visible. You might want to get one of those for home use only, if you're embarrassed to use it in public. I would say the ear infections are likely the cause. I wouldn't expect your hearing to get much worse until old age, however, but wouldn't expect it to improve, either.
2) Some type of brain damage could also make it difficult to interpret speech, but this doesn't seem to match what you've described. StuRat 02:30, 15 January 2007 (UTC)
hey i am another 14 year old and i had all my friends hear it none of them could hear the noise so mabe they have incorrect data at that site
Also the samples are aliased because of the low sampling rate. Try using audacity, crank the sampling rate all the way to the highest (100k) and generate the tones. -- antilived T | C | G 04:32, 15 January 2007 (UTC)
What sort of chemicals might these smart kids be using to create the fire in the bottle? Thanks for the help. -- 72.69.146.116 03:08, 14 January 2007 (UTC)
Of course, fish is nutritious. But why is the common stereotype that cats, rather than dogs love fish? Our article on cats says that domestic cats successfully hunt for fish. I have seen many swimming dogs, but never a swimming cat (despite the external link in our article). — Sebastian 03:31, 14 January 2007 (UTC)
What solutions would you suggest for a simple stepper motor controller? Ideally, the microcontroller should only have to send two bits: the direction and a pulse. The motor controller would then move the motor according to the input.
Most websites recommend the Allegro UCN5804B for this type of application, but it has been discontinued. The replacement (A3967) is unfortunately only available in a SOIC package (which is much harder to prototype).
Do you have any recommandations or suggestions for this project? -- Jcmaco 00:59, 16 January 2007 (UTC)
A PIC microcontroller might do this simple job-- Light current 03:51, 14 January 2007 (UTC)
Why mercury is used in a thermometer? Vichu satheesh 04:25, 14 January 2007 (UTC)
And, perhaps it's obvious, but you want a substance which is liquid over the entire range of temps you are likely to encounter, and one that won't break down with age or sunlight exposure. StuRat 02:10, 15 January 2007 (UTC)
In some cultures, a brass monkey is used. Apparently they are very sensitive to extreme cold. FT2 ( Talk | email) 09:06, 15 January 2007 (UTC)
hello,
I would like to know the manufacturing process of petrol with more details than the normal one paragrph process. being a chemical engineer and gonna pursue my studies in oil and i would like to have a strong backgroud. waiting for your reply.
thank you for your co-operation .
How is orbit not a perpetual motion device? The object is continuously falling, so therefore gravity should keep accelerating it, right?
Orbit is a perpetual motion system in the sense that moving through space is perpetual motion. It's not doing work, it's not producing net output of energy, it's just following a no gain/no loss path through space-time. You can see how "perpetual" orbit is, by watching what happens if even small amounts of atmosphere exist in a satellite's orbit. Eventually it will lose velocity, spiral and fall out of orbit. As said above, perpetual motion devices are intended to do some work, for example, to continue to move eternally despite having to offset friction, or to produce some form of net energy output. FT2 ( Talk | email) 09:02, 15 January 2007 (UTC)
...as a metaphor. A few hundred centimeters up, we spoke about boiling frogs as a metaphor. Another metaphor has been going around for a while (see Crab mentality, [9], or [10]
Ok, so if you're too lazy to click on the above, in short it is claimed that if there is an open bucket of live crabs, none would be able to escape, since if one tried to climb out, the others would pull it back. I've heard this used as a metaphor for someone who tries to get out of the 'hood, that the other members will do all they can to keep people from bettering themselves.
So, any fisherfolk out there that can vouch for this supposed behavio(u)r of crabs? Bunthorne 07:46, 14 January 2007 (UTC)
I am a photographer and have been doing infrared film photography since 1987. I was contributing to the Infrared photography article, and I came upon an assertion under the Film Cameras section that I could not confirm and that did not sound correct to me.
"Catadioptric lenses do not require this adjustment because mirrors do not suffer from chromatic aberration".
"This adjustment" refers to the refocus of a camera lens to compensate between visible light focus and infrared light focus. Is this correct? I just wanted to check since I teach infrared photography workshops and this would be good to know definitively. There are other optical assertions under Infrared photography that are so far out of my league I wouldn't know it they are right or wrong, but this one sounded odd. Thanks-- Schafphoto 08:12, 14 January 2007 (UTC)schafphoto
I notice from reading the woodpecker article that some species have zygodactyl feet (i.e. two toes forward and two toes back). Birds in the parrot family also have this configuration and are able to use their claws like hands to manipulate objects. Can woodpeckers do the same? -- Kurt Shaped Box 11:46, 14 January 2007 (UTC)
what is the actual fullform of Rx in medical sciences?—
how would an animal such as a polar bear adapt to the environment if it was taken fm the northpole and put in singapore??
If you mean in a zoo, they would be OK so long as they have some method to prevent overheating, like a nice pool to swim in. In the wild, however, their usual methods of hunting, such as pouncing on seals in their dens through the snow roof, just don't work. They can survive by stealing food from landfills, however, which they often do when their natural hunting methods fail them. StuRat 18:04, 14 January 2007 (UTC)
What are the effects on the human sense of hearing in total silence? Rick42774 14:13, 14 January 2007 (UTC)
People can often hear their own heart beat in such conditions (when not breathing). StuRat 17:49, 14 January 2007 (UTC)
Warning: Speculative comments ahead: - Although science does not have a definitive answer, I wouldn't discard the latter quite so quickly. There are a number of body processes and it's not impossible that some might give rise to the slight sensation of sound, or low level stimulation of the aural nervous or neural systems that might be interpreteted as 'sound' in a completely silent environment. Also I'm incined to not completely discredit the comment of some
mystics and
meditative practices who comment that the entire body's nature is
vibrative, with the solidity an illusion. Obviously at present that would not be considered a scientific observation, at best being
hearsay from some people. But Indian meditative practices contain meditation upon internal subtle sounds that might match cage's description. Again, unconfirmed, so take it for whatever it's worth.
FT2 (
Talk |
email)
08:58, 15 January 2007 (UTC)
Can you explain how the recently launched SRE-satellite vehicle by ISRO works and return back to earth without any damage by the viscosity of the air? 59.92.82.44 15:32, 14 January 2007 (UTC)
I have recently created an edit of Zebra Botswana.jpg for its featured picture attempt, and one of the major problems I have with the image is that the subspecies of Plain's Zebra (at least, I think that's the right species) isn't identified. It seems to match Burchell's Zebra, but I would like a second (and perhaps more knowledgeable) opinion. -- Pharaoh Hound (talk) 16:19, 14 January 2007 (UTC)
i was asked a while back and could not answer, so could someone tell me how they knew the casimir effect was caused by the zero point field and not by the gravity between the two plates. i know they did somehow but not how they distinguished this. can anyone help me? curious
Do they compute the spectrum width on the fly with some kinda DFT? tia --Ulisse0 14 January 2007 (UTC)
I think they just feel out where the signal is strong
I heard many times that Pluto is not a planet. Why? Sciencefordummies 19:40, 14 January 2007 (UTC)
I have several people about this and they said they have also wondered this, but had no definitive answer. Is the way I see light at 450–495 nm (blue) the same way someone else sees that wavelength light? So if I could see through someone else's eyes would their sky be the way I interpret red? Sorry if this doesn't make any sense, I'm not very good at explaining things. :-). Imaninjapirate talk to me 20:36, 14 January 2007 (UTC)
You should read up on tetrachromats. Due to mosaic x-inactivation some women are thought to have tetrachromatic vision. The result is that the resolution of different light frequencies is more acute and therefore more colours can be distinguished. David D. (Talk) 08:44, 15 January 2007 (UTC)
I have no idea what type of bird this is.
Bewareofdog 20:47, 14 January 2007 (UTC)
that bird is ugly —Preceding unsigned comment added by Rya Min ( talk • contribs) 18:04, 14 January 2007
Some of this post will probably contain bogus information, so please correct me
It is my understanding that time is essentially an illusion created by the fact that the universe tends to unfold in a certain direction, i.e. higher entropy. It is possible to go "backwards" in time but the chances of it happening are just so rare that it simply wouldn't happen - every single particle in the universe re-configuring to a previous state is just ridiculously statistically improbable.
But yet if an egg were to fall off a table and shatter on the floor but then by some freak chance reassemble back onto the table in a reverse direction, we wouldn't consider that we were going back in time, just that something very very rare had ocurred.
Put simply, there is no true direction of time we are just so used to it being one way due to the way matter predictably behaves and configures itself? 164.11.204.52 21:48, 14 January 2007 (UTC)
Which organ has the ability to monitor and regulate blood pressure and electrolytes:
A. LUNGS
B. HEART
C. KIDNEY
D. SPLEEN —Preceding
unsigned comment added by
72.40.72.252 (
talk •
contribs)
Hello. Okay, the thing is that our Sun currently is a "small" star but later it will become a red giant or supergiant in its final stages of its life. Now my question is, stars such as Antares, Arcturus and Aldebaran that are so huge... is it because they are "by nature" much more massive, big (in volume) and generally cold or are they just stars that are at the end of their lives? Of course some difference in mass between stars must exist, it would be too much of a coincidence if they were aproximately the same. What is what causes these differences? Thanks. -- Taraborn 23:54, 14 January 2007 (UTC)
Stars can have very great difference in mass when they form. That makes sense since mass is just "how much matter came together to make the star"; if it forms in a hydrogen-rich environment or not, for example. The mass is crucial to their fusion cycle, and hence to both the color of their light and also their history and fate. This is my basic understanding of the mechanism, someone more knowledgable may need to correct some of it:
Stars start by burning hydrogen to form helium. When the hydrogen is substantially burned, then ordinarily like most fires when the fuel runs low, the transformation of energy (in this case mass to energy by fusion) slows. The star was held in equilibrium between gravity (that is trying to force it to collapse) and heat production and other stellar processes (that provide pressure against contraction). As the hydrogen cycle slows, the latter reduces, and the star begins to collapse. When things are compressed it often results in a higher temperature (think of using a bicycle pump). If the star is big enough, this will generate enough temperature for helium fusion to occur, and the star will now have a helium burning core, with the hydrogen burning layer outside that. Because helium burns at a higher temperature, this is a hotter core, higher temperature, bluer light, and shorter lived. This can repeat several times for supermassive stars, with silicon, oxygen, and other fusions occuring in different layers. But when iron is being produced the process ends, because iron can't be fused this way - unlike lighter elements, there is no element which iron atoms can fuse to create, which would produce a net release of energy, because Iron is too stable in this sense.
So that's color. The size of a star is determined by mass and core temperature, so different stars and different masses and different stages in their fusion cycles, can have very different sizes. I don't know enough to comment on why and how that works in detail though, but the above I am broadly sure is fairly accurate.
The ultimate fate of a star depends again on the same things. Does it blow off its outer layers, does it collapse and become a nova or supernova or does it just fade once its hydrogen fuel runs out. Again, not sure exactly the details. But hopefully this has helped somewhat on one aspect anyway. FT2 ( Talk | email) 08:45, 15 January 2007 (UTC)
Science desk | ||
---|---|---|
< January 13 | << Dec | January | Feb >> | January 15 > |
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. |
My reading suggests that after an egg is fertilized in vivo, it is composed of stem cells that continue to divide at least until the egg attaches to the uterine wall. The write up under stem cells says "When given no stimuli for differentiation, ES cells will continue to divide in vitro and each daughter cell will remain pluripotent." The specific question is: Is this also true in vivo and what is the stimuli in vivo that begins the differentiation? The answer I am expecting is that it is something in the process that is initiated following attachment of the egg to the uterus that begins the next stage of embryonic development and if the egg does not attach, it degenerates and gets flushed with the next menstrual cycle.-- Billxm 00:23, 14 January 2007 (UTC)
I want to construct this model gun from sheet metal for laser-tagging purposes. Given that the diameter varies along the length of the gun, how might I accurately fold the metal? And ideas for making the gun handle, which I'd like to construct from the same metal? The blue part is a plastic window. >> gun<< -- Username132 ( talk) 00:23, 14 January 2007 (UTC)
If you use very thing sheet metal, you could maybe stretch it around a mold to get the desired shape. A ductile metal like copper would work best. If it's too thick to stretch, you may have to create a cylinder for the middle and two cones at the ends, to approximate the barrel shape. StuRat 04:29, 15 January 2007 (UTC)
I am doing a science fair project related to light pollution. I plan to zoom in on 'earth at night' maps located on the Internet and count the number of pixels in a certain 'area' (e.g. mid sized city) and see if light pollution naturally occurs in areas where there is population. Unfortunately, few (or no) maps on the Internet are reliable enough for me to look at (because of low res, no state or country boundaries, chance of being Photoshopped to make the image look 'better', etc...) and the process seems too tedious (city boundaries hard to 'distinguish', time in counting pixels, etc...). Can anyone help me, like introduced me to some special software or a good image (ahem...I mean really good, and better than the IDA stuff or the World Atlas of Night Brightness)? And if you can find the latter (an image) please give me a suggestion on how I can make the project less tedious. If you think I should have a new project, please keep it so I don't have to go outside during the nighttime or have to buy too many things. Thank you! —The preceding unsigned comment was added by Member ( talk • contribs).
Here's a nice map of the US with states shown: [2]. You can look at a political map for each state and figure out what each city is. StuRat 04:10, 15 January 2007 (UTC)
If I have a bottle of ice and water and want to drink the water -- will it help if I violently shake the bottle and splash the ice/water around?
I'm 14 years old but I seem to have hearing problems. I've always had the problem of hearing people talk, but never understanding what they are saying, especially when there is background noise or I am talking on the phone. This is obviously annoying because I either say what 5 times before understanding, or I just nod and say yes, not ever knowing what they just said. I also just listened to these high frequency " mosquito noises" on this website [4]. A teenager like me is supposed to be able to hear from 21.1 khz to 22.4 khz. I can only hear up to 14.9 khz, which is what people 39 and under are supposed to hear! I have never listened to music on earphones very loud for long periods of time and I don't go to loud concerts. However, I did have many ear infections and had to have ear tubes put in when I was young. Is my problem just going to get worse as as I get older? Maybe as far as though I will go deaf? Hopefully this doesn't count as medical advice. Thanks for your responses. :-). Imaninjapirate talk to me 02:05, 14 January 2007 (UTC)
Stop! Don't panic! Never use the computer to diagnose yourself or others. You didn't go into detail about how you listened to the tones. Unless you have a fantastic computer/audio system, you can't reliably test your hearing. The high frequencies won't get through most speakers. There's a good chance that you don't have a problem, but the only way to make sure is to have your hearing tested by a professional. Bunthorne 06:31, 14 January 2007 (UTC)
The two possibilities that come to mind to describe being able to hear but not able to distinguish words are:
1) Lack of high frequency hearing, as you suggested may be the problem in your case. I suggest having your hearing tested, and possibly using hearing aides. They can be small enough to hide within the ear canal, and can selectively amplify certain frequencies. Parabolic microphones also allow you to hear voices from one direction only, but those are, of course, highly visible. You might want to get one of those for home use only, if you're embarrassed to use it in public. I would say the ear infections are likely the cause. I wouldn't expect your hearing to get much worse until old age, however, but wouldn't expect it to improve, either.
2) Some type of brain damage could also make it difficult to interpret speech, but this doesn't seem to match what you've described. StuRat 02:30, 15 January 2007 (UTC)
hey i am another 14 year old and i had all my friends hear it none of them could hear the noise so mabe they have incorrect data at that site
Also the samples are aliased because of the low sampling rate. Try using audacity, crank the sampling rate all the way to the highest (100k) and generate the tones. -- antilived T | C | G 04:32, 15 January 2007 (UTC)
What sort of chemicals might these smart kids be using to create the fire in the bottle? Thanks for the help. -- 72.69.146.116 03:08, 14 January 2007 (UTC)
Of course, fish is nutritious. But why is the common stereotype that cats, rather than dogs love fish? Our article on cats says that domestic cats successfully hunt for fish. I have seen many swimming dogs, but never a swimming cat (despite the external link in our article). — Sebastian 03:31, 14 January 2007 (UTC)
What solutions would you suggest for a simple stepper motor controller? Ideally, the microcontroller should only have to send two bits: the direction and a pulse. The motor controller would then move the motor according to the input.
Most websites recommend the Allegro UCN5804B for this type of application, but it has been discontinued. The replacement (A3967) is unfortunately only available in a SOIC package (which is much harder to prototype).
Do you have any recommandations or suggestions for this project? -- Jcmaco 00:59, 16 January 2007 (UTC)
A PIC microcontroller might do this simple job-- Light current 03:51, 14 January 2007 (UTC)
Why mercury is used in a thermometer? Vichu satheesh 04:25, 14 January 2007 (UTC)
And, perhaps it's obvious, but you want a substance which is liquid over the entire range of temps you are likely to encounter, and one that won't break down with age or sunlight exposure. StuRat 02:10, 15 January 2007 (UTC)
In some cultures, a brass monkey is used. Apparently they are very sensitive to extreme cold. FT2 ( Talk | email) 09:06, 15 January 2007 (UTC)
hello,
I would like to know the manufacturing process of petrol with more details than the normal one paragrph process. being a chemical engineer and gonna pursue my studies in oil and i would like to have a strong backgroud. waiting for your reply.
thank you for your co-operation .
How is orbit not a perpetual motion device? The object is continuously falling, so therefore gravity should keep accelerating it, right?
Orbit is a perpetual motion system in the sense that moving through space is perpetual motion. It's not doing work, it's not producing net output of energy, it's just following a no gain/no loss path through space-time. You can see how "perpetual" orbit is, by watching what happens if even small amounts of atmosphere exist in a satellite's orbit. Eventually it will lose velocity, spiral and fall out of orbit. As said above, perpetual motion devices are intended to do some work, for example, to continue to move eternally despite having to offset friction, or to produce some form of net energy output. FT2 ( Talk | email) 09:02, 15 January 2007 (UTC)
...as a metaphor. A few hundred centimeters up, we spoke about boiling frogs as a metaphor. Another metaphor has been going around for a while (see Crab mentality, [9], or [10]
Ok, so if you're too lazy to click on the above, in short it is claimed that if there is an open bucket of live crabs, none would be able to escape, since if one tried to climb out, the others would pull it back. I've heard this used as a metaphor for someone who tries to get out of the 'hood, that the other members will do all they can to keep people from bettering themselves.
So, any fisherfolk out there that can vouch for this supposed behavio(u)r of crabs? Bunthorne 07:46, 14 January 2007 (UTC)
I am a photographer and have been doing infrared film photography since 1987. I was contributing to the Infrared photography article, and I came upon an assertion under the Film Cameras section that I could not confirm and that did not sound correct to me.
"Catadioptric lenses do not require this adjustment because mirrors do not suffer from chromatic aberration".
"This adjustment" refers to the refocus of a camera lens to compensate between visible light focus and infrared light focus. Is this correct? I just wanted to check since I teach infrared photography workshops and this would be good to know definitively. There are other optical assertions under Infrared photography that are so far out of my league I wouldn't know it they are right or wrong, but this one sounded odd. Thanks-- Schafphoto 08:12, 14 January 2007 (UTC)schafphoto
I notice from reading the woodpecker article that some species have zygodactyl feet (i.e. two toes forward and two toes back). Birds in the parrot family also have this configuration and are able to use their claws like hands to manipulate objects. Can woodpeckers do the same? -- Kurt Shaped Box 11:46, 14 January 2007 (UTC)
what is the actual fullform of Rx in medical sciences?—
how would an animal such as a polar bear adapt to the environment if it was taken fm the northpole and put in singapore??
If you mean in a zoo, they would be OK so long as they have some method to prevent overheating, like a nice pool to swim in. In the wild, however, their usual methods of hunting, such as pouncing on seals in their dens through the snow roof, just don't work. They can survive by stealing food from landfills, however, which they often do when their natural hunting methods fail them. StuRat 18:04, 14 January 2007 (UTC)
What are the effects on the human sense of hearing in total silence? Rick42774 14:13, 14 January 2007 (UTC)
People can often hear their own heart beat in such conditions (when not breathing). StuRat 17:49, 14 January 2007 (UTC)
Warning: Speculative comments ahead: - Although science does not have a definitive answer, I wouldn't discard the latter quite so quickly. There are a number of body processes and it's not impossible that some might give rise to the slight sensation of sound, or low level stimulation of the aural nervous or neural systems that might be interpreteted as 'sound' in a completely silent environment. Also I'm incined to not completely discredit the comment of some
mystics and
meditative practices who comment that the entire body's nature is
vibrative, with the solidity an illusion. Obviously at present that would not be considered a scientific observation, at best being
hearsay from some people. But Indian meditative practices contain meditation upon internal subtle sounds that might match cage's description. Again, unconfirmed, so take it for whatever it's worth.
FT2 (
Talk |
email)
08:58, 15 January 2007 (UTC)
Can you explain how the recently launched SRE-satellite vehicle by ISRO works and return back to earth without any damage by the viscosity of the air? 59.92.82.44 15:32, 14 January 2007 (UTC)
I have recently created an edit of Zebra Botswana.jpg for its featured picture attempt, and one of the major problems I have with the image is that the subspecies of Plain's Zebra (at least, I think that's the right species) isn't identified. It seems to match Burchell's Zebra, but I would like a second (and perhaps more knowledgeable) opinion. -- Pharaoh Hound (talk) 16:19, 14 January 2007 (UTC)
i was asked a while back and could not answer, so could someone tell me how they knew the casimir effect was caused by the zero point field and not by the gravity between the two plates. i know they did somehow but not how they distinguished this. can anyone help me? curious
Do they compute the spectrum width on the fly with some kinda DFT? tia --Ulisse0 14 January 2007 (UTC)
I think they just feel out where the signal is strong
I heard many times that Pluto is not a planet. Why? Sciencefordummies 19:40, 14 January 2007 (UTC)
I have several people about this and they said they have also wondered this, but had no definitive answer. Is the way I see light at 450–495 nm (blue) the same way someone else sees that wavelength light? So if I could see through someone else's eyes would their sky be the way I interpret red? Sorry if this doesn't make any sense, I'm not very good at explaining things. :-). Imaninjapirate talk to me 20:36, 14 January 2007 (UTC)
You should read up on tetrachromats. Due to mosaic x-inactivation some women are thought to have tetrachromatic vision. The result is that the resolution of different light frequencies is more acute and therefore more colours can be distinguished. David D. (Talk) 08:44, 15 January 2007 (UTC)
I have no idea what type of bird this is.
Bewareofdog 20:47, 14 January 2007 (UTC)
that bird is ugly —Preceding unsigned comment added by Rya Min ( talk • contribs) 18:04, 14 January 2007
Some of this post will probably contain bogus information, so please correct me
It is my understanding that time is essentially an illusion created by the fact that the universe tends to unfold in a certain direction, i.e. higher entropy. It is possible to go "backwards" in time but the chances of it happening are just so rare that it simply wouldn't happen - every single particle in the universe re-configuring to a previous state is just ridiculously statistically improbable.
But yet if an egg were to fall off a table and shatter on the floor but then by some freak chance reassemble back onto the table in a reverse direction, we wouldn't consider that we were going back in time, just that something very very rare had ocurred.
Put simply, there is no true direction of time we are just so used to it being one way due to the way matter predictably behaves and configures itself? 164.11.204.52 21:48, 14 January 2007 (UTC)
Which organ has the ability to monitor and regulate blood pressure and electrolytes:
A. LUNGS
B. HEART
C. KIDNEY
D. SPLEEN —Preceding
unsigned comment added by
72.40.72.252 (
talk •
contribs)
Hello. Okay, the thing is that our Sun currently is a "small" star but later it will become a red giant or supergiant in its final stages of its life. Now my question is, stars such as Antares, Arcturus and Aldebaran that are so huge... is it because they are "by nature" much more massive, big (in volume) and generally cold or are they just stars that are at the end of their lives? Of course some difference in mass between stars must exist, it would be too much of a coincidence if they were aproximately the same. What is what causes these differences? Thanks. -- Taraborn 23:54, 14 January 2007 (UTC)
Stars can have very great difference in mass when they form. That makes sense since mass is just "how much matter came together to make the star"; if it forms in a hydrogen-rich environment or not, for example. The mass is crucial to their fusion cycle, and hence to both the color of their light and also their history and fate. This is my basic understanding of the mechanism, someone more knowledgable may need to correct some of it:
Stars start by burning hydrogen to form helium. When the hydrogen is substantially burned, then ordinarily like most fires when the fuel runs low, the transformation of energy (in this case mass to energy by fusion) slows. The star was held in equilibrium between gravity (that is trying to force it to collapse) and heat production and other stellar processes (that provide pressure against contraction). As the hydrogen cycle slows, the latter reduces, and the star begins to collapse. When things are compressed it often results in a higher temperature (think of using a bicycle pump). If the star is big enough, this will generate enough temperature for helium fusion to occur, and the star will now have a helium burning core, with the hydrogen burning layer outside that. Because helium burns at a higher temperature, this is a hotter core, higher temperature, bluer light, and shorter lived. This can repeat several times for supermassive stars, with silicon, oxygen, and other fusions occuring in different layers. But when iron is being produced the process ends, because iron can't be fused this way - unlike lighter elements, there is no element which iron atoms can fuse to create, which would produce a net release of energy, because Iron is too stable in this sense.
So that's color. The size of a star is determined by mass and core temperature, so different stars and different masses and different stages in their fusion cycles, can have very different sizes. I don't know enough to comment on why and how that works in detail though, but the above I am broadly sure is fairly accurate.
The ultimate fate of a star depends again on the same things. Does it blow off its outer layers, does it collapse and become a nova or supernova or does it just fade once its hydrogen fuel runs out. Again, not sure exactly the details. But hopefully this has helped somewhat on one aspect anyway. FT2 ( Talk | email) 08:45, 15 January 2007 (UTC)