Aces High Bulletin Board
General Forums => The O' Club => Topic started by: Meatwad on July 05, 2005, 09:05:34 PM
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Back when, how did they come up with the answer that the speed of light travels 186,000 miles/second? What if the number is really a different number, and all calculations to different stars/systems are actually closer or farrther away?
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see rule # 7
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The speed of light is a theory. Theories are insurance against actually having to be right.
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I always thought that the speed of light was a variable....it has mass and can be affected by gravity.
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Speed of light is a constant.
http://en.wikipedia.org/wiki/Speed_of_light
Reference the Wikipedia. One of the greatest inventions of the information age. :)
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In a sense, any light travelling through a medium other than a vacuum travels below c as a result of refraction. However, certain materials have an exceptionally high refractive index: in particular, the optical density of a Bose-Einstein condensate can be very high. In 1999, a team of scientists led by Lene Hau were able to slow the speed of a light beam to about 17 metres per second, and, in 2001, they were able to momentarily stop a beam.
Ok...this is what I was think of...
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Heres how the speed of light was determined, I guess:
http://www.colorado.edu/physics/2000/waves_particles/lightspeed_evidence.html (http://www.colorado.edu/physics/2000/waves_particles/lightspeed_evidence.html)
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Lets say there was a planet that is 1/10 light year away (for a close mission), given the speed of light is 186,000 miles/sec. The planet is stationary, neither moving farther nor closer from the launch point of a vehicle heading to investigate it.
Given the speed of the vehicle as a constant, the vehicle travels to the star with an estimated arrival date derived from the vehicles speed in relation to the speed of light.
If the vehicle arrives there not on its estimated date, but the actual arrival date, this would prove the speed of light is no longer its current value, but a totally different number.
But also if it can be proven lightspeed is infact a varible, this would totally throw current measurements out the window as the possible distance can not be accurately measured between two bodies.
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Originally posted by JB66
Ok...this is what I was think of...
Which is not actually a measure of the speed of light, its a measure of the refractive index of a substance affecting a light beam.
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I remember reading an article stating that gravity affects the speed of light...something along the line of a black hole(keep it clean guys) bending light back into the event horizon.
It's been awhile, and I don't really remember where I read it...
I Could be confusing several theories...I haven't read anything on it in years.
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Meatwad, I could just as easily say that calling the color of the sky "blue" is totally subjective because it relys on our interpretation of color. Another species that sees color differently might see the sky as yellow. So therefore we shouldnt call the sky "blue".
Irregardless of what we see or someone else sees, the reflected wavelength of light that gives the sky "color" remains constant. You can call it anything you please. The POV being different also makes no difference, except to the viewer. Calling it yellow or calling it blue doesnt mean its different, if we understand that their yellow = our blue.
You can try to twist the words around all you like. But at this stage of the game, c is a constant in all physics equations, and in all applications as well.
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the speed of light more than likely is infact a variable. Only if it passes by an large object (aka sun) blacks suck light in from its gravity so i don't think it can be a constant.
bu hey in an 11th grader.
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The speed of light is a constant. A constant cannot be variable. It is not a theory. The speed of light is constant, regardless of whether you are approaching or receding from the source.
If you are interested in physics, I urge you to talk to your teacher or read some books to understand that it is a fundamental constant and building block to appreciating and understanding science and physics. You cannot advance to calculus-based physics without this understanding. You cannot become an engineer without this fundamental understanding.
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Light is an additive system and consists of a color spectrum, each color having a different wavelength. The primary additive colors are CYAN, MAGENTA and VIRIDIAN.
This is caused by our sun and may be different in space. There is no color in space (or very little of it, a space voyage would be boring in that sense except for color enhancement devices.)
It is the bending of light in our atmosphere that causes color, it slows down a bit when refracted and we see it.
However, light is so fast most times we cannot see it, or may not be able to in space. I don't think light slows down or changes speed enough for mathematic applications, but I'd venture to guess it does vary slightly in speed.
Les
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Well it's all relative..................... ............I'll get my coat:(
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Originally posted by JB66
I remember reading an article stating that gravity affects the speed of light...something along the line of a black hole(keep it clean guys) bending light back into the event horizon.
It's been awhile, and I don't really remember where I read it...
I Could be confusing several theories...I haven't read anything on it in years.
Gravity doesn't affect light. Light doesn't slow down. Space is curved and that can be detected near large objects in space by viewing light from a distant star around the edge of the large object before you should, in theory, see it.
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Danish physicist Lene Hau, brought light waves down to a 1 mph crawl by putting
them through a specially prepared haze of ultracold sodium atoms.
Some of the physicists accomplished what sounds like an impossible task:
slowing down a light pulse so much that it appears to fade and stop, then starting
it up again on demand.
looks like an easy task ! ;)
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I read this
(http://images-eu.amazon.com/images/P/0552997048.02.LZZZZZZZ.jpg)
And I still don't get it! :confused:
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Here is an intresting read:
http://www.newscientist.com/article.ns?id=dn6092
The speed of light, one of the most sacrosanct of the universal physical constants, may have been lower as recently as two billion years ago - and not in some far corner of the universe, but right here on Earth.
The controversial finding is turning up the heat on an already simmering debate, especially since it is based on re-analysis of old data that has long been used to argue for exactly the opposite: the constancy of the speed of light and other constants.
A varying speed of light contradicts Einstein's theory of relativity, and would undermine much of traditional physics. But some physicists believe it would elegantly explain puzzling cosmological phenomena such as the nearly uniform temperature of the universe. It might also support string theories that predict extra spatial dimensions.
and
Lizard was correct in stating that space is curved.
http://imagine.gsfc.nasa.gov/docs/ask_astro/answers/961102.html
Enter Albert Einstein. In 1915 he proposed the theory of general relativity. General relativity explained, in a consistent way, how gravity affects light. We now knew that while photons have no mass, they do possess momentum (so your statement about light not affecting matter is incorrect). We also knew that photons are affected by gravitational fields not because photons have mass, but because gravitational fields (in particular, strong gravitational fields) change the shape of space-time. The photons are responding to the curvature in space-time, not directly to the gravitational field. Space-time is the four-dimensional "space" we live in -- there are 3 spatial dimensions (think of X,Y, and Z) and one time dimension.
I've got to stop combining stuff I've read...it gets confusing.
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Originally posted by Lizard3
Gravity doesn't affect light. Light doesn't slow down.
wrong...it does affect its speed, much like a sling shot, Einstien was in favor of a static universe, hence the constant speed of light in his theories...
graviton vs. photon, graviton wins
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The speed of light, c, was proven not to be constant a few years back.. Gravity has been proven to be able to bend light as well as influence it's speed..
My understanding is light is made up of photons. Photons have a mass thereby are affected by gravity..
The speed of light can still be a relative measurement for distants or time..
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TheDudeDVant: Light is treated as a particle-wave duality. Both are used in quantum mechanics, depending on the calculation required. Sometimes light appears to act as a wave and other times a particle. The uncertainty principle is the tape the binds the two together.
There were a few papers presented or published a decade or so ago proposing that c has slowed over time, but something as remarkable and with such a profound effect on physics would have surely been vetted and explored by now. No physicist of note or professional organization has endorsed the theory.
Light propogation is still accepted as a constant and what some have latched onto as evidence of a variable c over time can be explained by considering universe (time and space) expansion over time - not decay of c.
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as for the original question... i forgot which old scientist, but like plato or something WAY back when...
put a candle somewhere on a mountian, and a rotating mirror on another mountian 7 miles away or something....
he calculated the speed of light back then by timing the reflected candle in the mirror. i dont believe how it was done, but that's what i have learned a long time ago, and saw even recently on the history channel or something
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its all relative, in a offhand way.
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Gravity does not really bend light beams. It bends space. The light still travels in a straight line, but the space within which "straight' is defined is bent.
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Originally posted by TheDudeDVant
The speed of light, c, was proven not to be constant a few years back.. Gravity has been proven to be able to bend light as well as influence it's speed..
My understanding is light is made up of photons. Photons have a mass thereby are affected by gravity..
The speed of light can still be a relative measurement for distants or time..
Lene Hau (http://www.news.harvard.edu/gazette/1999/02.18/light.html) would agree.
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Originally posted by Holden McGroin
Gravity does not really bend light beams. It bends space. The light still travels in a straight line, but the space within which "straight' is defined is bent.
So my question would be..
Can gravity influence time as well?
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Originally posted by Gh0stFT
Danish physicist Lene Hau, brought light waves down to a 1 mph crawl by putting
them through a specially prepared haze of ultracold sodium atoms.
Some of the physicists accomplished what sounds like an impossible task:
slowing down a light pulse so much that it appears to fade and stop, then starting
it up again on demand.
looks like an easy task ! ;)
Again, that is not really a measure of the speed of light "c", it is a measure of the refractive indexes of the substances the light went through. What you are talking about is NOT the "speed of light", the constant, c, it is the speed of light in a medium other than a vacuum. Those are different animals. Sort of. In other words, c is a constant, the speed of c in air is slightly less because of outside forces acting on it. Here, this explains it better.
Interaction with transparent materials
The refractive index of a material indicates how much slower the speed of light is in that medium than in a vacuum. The slower speed of light in materials can cause refraction, as demonstrated by this prism (in the case of a prism splitting white light into a spectrum of colours, the refraction is known as dispersion).In passing through materials, light is slowed to less than c by the ratio called the refractive index of the material. The speed of light in air is only slightly less than c. Denser media, such as water and glass, can slow light much more, to fractions such as 3/4 and 2/3 of c. This reduction in speed is also responsible for bending of light at an interface between two materials with different indices, a phenomenon known as refraction.
Since the speed of light in a material depends on the refractive index, and the refractive index depends on the frequency of the light, light at different frequencies travels at different speeds through the same material. This can cause distortion of electromagnetic waves that consist of multiple frequencies, called dispersion.
Note that the speed of light referred to is the observed or measured speed in some medium and not the true speed of light (as observed in vaccuum). On the microscopic scale, considering electromagnetic radiation to be like a particle, refraction is caused by continual absorption and re-emission of the photons that compose the light by the atoms or molecules through which it is passing. In some sense, the light itself travels only through the vacuum existing between these atoms, and is impeded by the atoms. The process of absorption and re-emission itself takes time thereby creating the impression that the light itself has undergone delay (i.e. loss of speed) between entry and exit from the medium in question. It may be noted, that once the light has emerged from the medium it changes back to it's original speed and this is without gaining any energy. This can mean only one thing - that the light's speed itself was never altered in the first place. Alternatively, considering electromagnetic radiation to be like a wave, the charges of each atom (primarily the electrons) interfere with the electric and magnetic fields of the radiation, slowing its progress.
(http://upload.wikimedia.org/wikipedia/en/f/fb/PrismAndLight.jpg)
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Originally posted by SLO
wrong...it does affect its speed, much like a sling shot, Einstien was in favor of a static universe, hence the constant speed of light in his theories...
graviton vs. photon, graviton wins
No, the constant speed of light is not just because of Einsteins preconceived notion. Relativity cause Albert to rethink many of his notions. The speed of light is a constant because experiments have shown it to be so. That under certain circumstances we could alter it does not effect the speed through deep space.
Gravity "bends" light, not because photons have mass, as they do not have mass, but because gravity effects the shape of spacetime.
Light "bends" because the fabric of space through which light travels is bent.
Light is travelling a straight path trough warped space.
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Originally posted by StarOfAfrica2
(http://upload.wikimedia.org/wikipedia/en/f/fb/PrismAndLight.jpg)
Cool! "The Dark Side of the Moon" Album cover!
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Originally posted by Holden McGroin
Gravity "bends" light, not because photons have mass, as they do not have mass, but because gravity effects the shape of spacetime.
Photons do not have any resting mass is as much as we can say about their mass.
Edit: Was thinking a bit more. Photons do have momentum, which is classicly = mass * velocity, however, we're dealing with relativity/quantum mechanics, so classic mechanics are off....but, sort of makes the point that we can only say they don't have a resting mass....
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While you are correct, rest mass of a particle which by definition must move is somewhat a useless concept.
If an object at rest has a mass M, moving at a speed v it will have a mass M/sqrt(1 - vē/cē). As an object approaches the speed of light, the mass increases without limit.
Because photons are light they are not at rest... they are moving at the speed of light. Therefore, since a photon travels at the limit of speed, it must either have no mass or relativity says it's mass is infinite.
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Originally posted by TheDudeDVant
So my question would be..
Can gravity influence time as well?
Yep.
Clocks do not tick in a black hole. (forgetting that the clock would be destroyed anyway.)
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And then there's the fact that we're relying on un-perfect balls of flesh to perceve it on. What we believe to be the speed of light, whether it's proven or rightfully debated, may be different from what a perfect measuring "eyeball" would see. And yet, there is no such thing.
Man that sounded nerdy.
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You misspelled "perceive" so at least you aren't perfect.;)
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Pishaw, it was a typo. I meant to spell it as "perceive."
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Originally posted by Meatwad
Back when, how did they come up with the answer that the speed of light travels 186,000 miles/second? What if the number is really a different number, and all calculations to different stars/systems are actually closer or farrther away?
I'm sorry squaddie, but you obviously have far too much free time on your hands.
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That and when I am tired and bored, I like to think about complex stuff like that.
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The speed of light is no more constant then the length of a meter. It is precisley what we say it is, no more, no less.
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Originally posted by JB66
In 1999, a team of scientists led by Lene Hau were able to momentarily stop a beam.
Ok...this is what I was think of...
i accomplish on a daily basis, multiple times, what it takes a team of scientists to achieve.
it's called...
flipping the switch.
sheesh... :rolleyes:
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Originally posted by TheDudeDVant
So my question would be..
Can gravity influence time as well?
ask any middle-aged person...
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lemme ask Scotty..
Scotty:dammit captain she's giving all she's got!
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Originally posted by ASTAC
Cool! "The Dark Side of the Moon" Album cover!
Beat me to it!
Karaya
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Originally posted by TheDudeDVant
So my question would be..
Can gravity influence time as well?
Ah, alas I do not know. I do know that speed affects time, like the Stein said, Dude 20 years old travels to a place 20 light years away at light speed and comes back home everyone is a hundred, but Dude is only 25. So, the faster you go the slower you age. Run everywhere, drive really really fast or fly if possible and you will stay young...or die fast.
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I believe they clocked light back in 1972 in the salt flats..at 185,968...they were gonna try for the 186,000 but had a broken part and had to call it a day.