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This page covers archived discussion up to the end of 2004
If I am at the Sun, and want to travel to the Earth at just a bit over the speed of light, what is to stop me? Light from the sun will get to the Earth in 8 min. So say that I leave when that ray of light leaves. I will get to the sun, say, in 7 min. So I am there i min ahead of the light. But light and time are not connected in any way. Time does not pass just because light is there. I will be at the Earth 7 min after I left the sun, which means that 7 min will have passed on Earth.
The article currently gives "The speed of light is of relevance to communications. For example, given that the equatorial circumference of the Earth is 40,075 km and c, the theoretical shortest amount of time for a piece of information to travel half the globe is 0.067 seconds." Though not particularly well-versed in physics, I believe the circumference of the Earth shouldn't play into this calculation (see this section's heading title). I don't disagree with that the quotation apparently gives the theoretical shortest amount of time for light to travel across the Earth circumferentially. However, since AFAIK a piece of information could be encoded in any number of frequencies of electromagnetic radiation (and that radiation could penetrate the Earth), the actual shape of interest is a straight line between opposite poles of the planet, not the circumference between them. 07:04, 22 Dec 2004 (UTC). Light second gives "The mean diameter of the Earth is 0.0425 light seconds". I feel this is a more relevant measure and recommend said part of the article be rewritten using it. 07:44, 22 Dec 2004 (UTC) Further data, from Ping: "To have some comparison for internet ping times, consider that the shortest possible ping to the other side of our planet is 95 ms. That is because 95 ms is the time the light needs to travel to the other side and back in a straight line through the earth. No signal can travel faster than light. The shortest possible ping would be 133 ms if we avoided a subterranean route." 12.223.239.28 05:02, 23 Dec 2004 (UTC)
The following needs to be reworked to make it fit in the context of an encyclopedia article. As it is it is a bit too chatty.
As a layman, I don't understand how it's possible for something to travel faster than c but not carry information faster than c. Could someone explain this? -- User:Evercat
Irrelevant. The electrons involved in the Cherenkov effect are still going slower than c. (It is true that light travels even slower than those electrons in that medium).
Sure. Take a laser pointer. Make a spot on the moon. Then turn your wrist to make a spot on the earth. It takes over a second for light to travel from the moon to the earth, yet I can move that little spot the same distance in far less than one second. -- 68.229.240.25 03:54, 20 Jul 2004 (UTC)
Similar, probably better, explanations:
"It is a solution to the wave equation"
If I understood correctly. <- This sentence was written by me.
Κσυπ Cyp 21:30, 16 Nov 2003 (UTC) The rest wasn't. -> Faster than light transmission of information follows some uncertainty principals, it also sidesteps a couple rules. When information is transmitted at such speeds, it can never be proven that the light recieved is the light that was transmitted. Photons subjected to this process have their frequency changed, their overall energy content is different due to the processes that caused this feat. However, if those people in line were to shout in sequence, the information would have to be previously known, this caused it's own speculation. As with the noted experiment of 300c, the photons arrived faster than light accounts for, the arrival of the photons is information, it arrived at it's destination faster than C, there IS NO explanation. - GouRou
Wile, why are you removing the scientific notation approximation? In 99% of cases when I'm performing a calculation involving the speed of light, the number I'm looking for is 3 × 108. I'm pretty sure this approximation, in this format, is useful to other people as well. Fredrik (talk) 18:49, 8 Jun 2004 (UTC)
I think that perhaps it should be clearly stated that by adding two velocities with the Einstein velocity addition formula we cannot get a speed greater than c. (Because the interval (-c,c) with that operation is an Abelian group.) I know that its said that c is a "speed limit" but what its not said is that the formula is consistent with that. -- ReiVaX 18:09, 18 Jul 2004 (UTC)
The article currently says:
I'm fairly certain that is correct for "distance", but incorrect for "time". If you read http://www.bldrdoc.gov/timefreq/general/precision.htm#Anchor-60273 carefully, you see that "transitions of the cesium atom" are the reference for time, not the speed of that light.
Suggested replacement:
For a Featured Article this should have some graphics. Yes, I know it it is hard to find a good graphic for speed of light, but perhapse Google Image search will have something we can use? -- Piotr Konieczny aka Prokonsul Piotrus 21:37, 31 Jul 2004 (UTC)
In Two New Sciences Galileo claimed to have performed his experiment, not just proposed it (though in a more ambiguous way than I'd realized); he also said explicitly, long before Hooke, that his experiment couldn't prove that the speed was infinite. Assuming he did perform it, this is the first known case of anyone's trying to make an actual measurement of the speed. The criticism by Descartes is interesting and looks as if it would be valid; does anyone know the argument in enough detail to say? Dandrake 08:25, Aug 6, 2004 (UTC)
According to the theory of special relativity, all observers will measure the speed of light as being the same, regardless of the reference frame of the observer or the velocity of the object emitting the light. A simple three-step analysis is sufficient to show that this is the case:
The constant speed of light derives from the Lorentz transforms, which distort distances and times for observers travelling at large velocities in the same way.
Isn't 3 precisely what we are trying to show is the case? "all observers will measure the speed of light as being the same" because "observers in all such frames must observe the same speed of light"? Also, as the speed of light in a vaacum is a defined value, the fact that it can be derived from Maxwell's equations needs to be explained. anthony (see warning) 19:00, 12 Aug 2004 (UTC)
I guess I see what is being said. 3 is the conclusion from 1 and 2. This seems to be worded strangely, though. anthony (see warning) 19:41, 12 Aug 2004 (UTC)
As you've perhaps seen I've already made a number of copyedits. This one I'm not sure how to reword, though, in part because I'm not 100% sure what the point is. anthony (see warning) 20:12, 12 Aug 2004 (UTC)
The article looks great! But... (ther's always a but):
(a) in 1: «The constant speed of light derives from the Lorentz transforms, which distort distances and times for observers travelling at large velocities in the same way» - I think it's the other way around. The Lorentz transforms derives from Maxwell's equations and Einstein's constant speed of light postulate.
(b) in 4.1: «Einstein took [the Michelson-Morley experiment] result as a given fact» contradicted by «It is uncertain whether Albert Einstein knew the results of the Michelson-Morley experiment» (in 5.4). - I don't know wich is true.
(c) I failed to understand the concept of "light slowing". Can someone elaborate on that?--
Nabla 00:12, 2004 Aug 13 (UTC)
I am the speed of light
An anon recently added the following:
At first it sounded like pseudoscience, but a quick google search turned up a number of references that at least appeared to have a chance to be legit. Is anyone else more familiar with this? - Taxman 20:15, Sep 13, 2004 (UTC)
I'd like to add my request for a bit more clarification on that point, either in this page or in a link. I've heard of the idea that the speed of light was higher at the beginning of the universe, then decayed to the current level and is now constant, but that particular concept is a load of creationist hogwash (see http://www.talkorigins.org/faqs/c-decay.html ). The only person behind they theory mentioned in the above link is one Barry Setterfield, not either of the two names in this article. Is this a different (and more reputable) theory? Should there be something in there (or in a link) explaining so, if they are different? - Mokele 17:00, Oct 2 2004
A changing speed of light has been proposed to explain observations of "the accelerating Universe". Link at: http://www-conf.slac.stanford.edu/einstein/Talks/aspauthor2004_3.pdf
If it is left in, I hope that someone could square it with the following: "This exact speed is a definition, not a measurement, as the metre is defined in terms of the speed of light and the second." If the speed is defined to be <so big> how can it vary? -- a different anon.
The page node (a disambig page) is currently in the process of being successfully split. Which use of the word "node" should be linked to in this sentence: "The speed of light can also be of concern on short distances. In supercomputers, the speed of light imposes a limit on how quickly data can be sent between nodes"? -- MatrixFrog 07:15, 19 Sep 2004 (UTC)
Hello all. This is a great article, thanks to everyone who has worked on it. I wonder if we really need the picture at the top of the article. It shows two nerdy guys playing with a laser, which is fun, but beside the point. Can we find another picture that directly addresses the topic? The caption does state something interesting about the speed of light but, strangely enough, doesn't describe something illustrated in the picture. Maybe someone can state what it is about the speed of light that it illustrates. Regards & happy editing, Wile E. Heresiarch 13:52, 11 Oct 2004 (UTC)
I agree that the image on top is not good enough. It does not demonstrate the speed of light at all, although it looks somewhat fancy. But an encyclopedia should have a more illustrative image. I tried to find a PD image of light refraction in a prism. What about this one. -- [[User:Solitude| Solitude\ talk]] 08:48, Oct 29, 2004 (UTC)
Also, the image used on top at the moment does not seem to be free at all. It is used with permission, but it is not stated how far this permission reaches. Can it be used commerially at all? As far as I know we can't use NC images, especially in featured articles, especially on TOP. -- [[User:Solitude| Solitude\ talk]] 08:53, Oct 29, 2004 (UTC)
I have noticed that the article uses both spellings. Which is the appropriate spelling for this article?
I don't think this is sufficient:
Experiments show that the second particle takes up its quantum state instantaneously, as soon as the first observation is carried out. However, it is impossible to control which quantum state the first particle will take on when it is observed, so no information can be transmitted in this manner.
The telegraph is able to transmit information, and it also provides no control of the state that the remote key will take when observed; all the operator can control is when the key will move.
The real reason information can't be transmitted this way must be more subtle. -- Doradus
The phrasing "speed of light ... is less than c due to the refractive index." suggests to me at least that the refractive index is some sort of phenomenon that causes the SOL to be lower in some medium, when it is really defined as a measure of how much slower light moves through a particular medium than through vacuum. I suggest a re-phrasing to avoid the possible confusion. Even to just say "... is less than c (see refractive index)" would be better in my opinion. -- Schnolle 10:46, 29 Oct 2004 (UTC)
In a recent article I read that understood "speed of light" has been altered to a considerable faster speed. Perhaps the creater of this page might want to address that note, althought it is my understanding for the sake of physic's discussions the speed of 186K MPS is still the accepted number.
I've reverted to put back the image of Cherenkov radiation as the lead image: a featured article ought to have a lead image, and this is the best example I can think of the image the actually shows "the speed of light" in a visible form. But I'd happily defer if someone can think of a better example. -- ALoan (Talk) 11:30, 16 Dec 2004 (UTC)
Well, I do not have any proof or any references that support what I am going to say. It is just something at the back of my mind that refuses to accept speed of light is the maximum speed attainable. All the formulas, explanations and examples of the formulas that I have come across always came back to point out that nothing could travel faster than speed of light: either the mass becomes infinity or something went into an imaginary number (square-root of negative one). For some reason, nothing I have read could explain to me what is the meaning of imaginary number with respect to physical manifestation (ps: imaginary number is not the number you imagine :D ). The only thing I know is that imaginary number is used in wave theory and in math when converting from one coordinates to another such as cartesian vs polar coordinates. Does it mean things that travel faster than light are all in wave or can be explained in wave theories?
Well, the good news is that after reading this article about the speed of light, some of what I believed has been affirmed --- speed of light is just like speed of sound: it is constant in a given medium. Light in each medium has its own speed. I have argued about this with my roommates for many weeks sometime in the early 1980s till we agreed to disagree. We were college students then. My roommates had GPA close to 4.0 while mine was closer to 2.8. They quoted a few theories that stated speed of light was absolute and constant regardless of medium. I was not convinced.
However, there is still one more unresolved issue. I believe, just like speed of sound, there are things out there that can travel faster than speed of light and capable of carrying meaningful information. From what I have read, this is contrary to the currently accepted view of things.
Here is my basic reasoning: speed of light is the maximum speed that we, as a human being, can perceive. Every single one of our observations were based on light --- we use our eyes to see every single one of our experiments, measurements and results. In addition, our brains are used to translating everything around us into the terms we understand --- both consciously and sub-consciously. These two combined, I believe, is the reason for the "distortions" that we perceive when an object approaches the speed of light.
Well, many of you will argue that our instrument are not affected and should show us the truth. Well, I have a few "arguments" to that. Some of the arguments is based on the fact that we "see" things from bounced light which, in itself, distort what we see. Here are the arguments:
Well, I hope someone can convince me that those scientists have removed/nullified/compensated the effect of light from their experiments. If so, I would like to know how they did it instead of saying that they just did. Personally, I hope I am right: Speed of light is just like speed of sound --- something we can safely exceed if we have the technology. If so, it will open up a lot of possibilities. I am, however, open to suggestions.
Food for thought: What makes you think you have not seen anything that moves faster than speed of light? Do you know how they look like? Do you think those unduplicated and unexplained "blips" or errors on an otherwise perfect experiments that "you can safely ignore" are really errors or ..... (For example, how do you detect a car travelling at 100 KPH with a pellet gun fired at 1 bullet per second perpendicular to the direction of the car's travel at a fixed point on the road? Will you take the bounce of a bullet versus a hundred that went through the air as the desired result or an error?)
Anyway, have fun everyone.
Regards, The Wondering Mind Sept. 7, 2005
Well, I do not have any proof or any references that support what I am going to say. It is just something at the back of my mind that refuses to accept speed of light is the maximum speed attainable. All the formulas, explanations and examples of the formulas that I have come across always came back to point out that nothing could travel faster than speed of light: either the mass becomes infinity or something went into an imaginary number (square-root of negative one). For some reason, nothing I have read could explain to me what is the meaning of imaginary number with respect to physical manifestation (ps: imaginary number is not the number you imagine :D ). The only thing I know is that imaginary number is used in wave theory and in math when converting from one coordinates to another such as cartesian vs polar coordinates. Does it mean things that travel faster than light are all in wave or can be explained in wave theories?
Well, the good news is that after reading this article about the speed of light, some of what I believed has been affirmed --- speed of light is just like speed of sound: it is constant in a given medium. Light in each medium has its own speed. I have argued about this with my roommates for many weeks sometime in the early 1980s till we agreed to disagree. We were college students then. My roommates had GPA close to 4.0 while mine was closer to 2.8. They quoted a few theories that stated speed of light was absolute and constant regardless of medium. I was not convinced.
However, there is still one more unresolved issue. I believe, just like speed of sound, there are things out there that can travel faster than speed of light and capable of carrying meaningful information. From what I have read, this is contrary to the currently accepted view of things.
Here is my basic reasoning: speed of light is the maximum speed that we, as a human being, can perceive. Every single one of our observations were based on light --- we use our eyes to see every single one of our experiments, measurements and results. In addition, our brains are used to translating everything around us into the terms we understand --- both consciously and sub-consciously. These two combined, I believe, is the reason for the "distortions" that we perceive when an object approaches the speed of light.
Well, many of you will argue that our instrument are not affected and should show us the truth. Well, I have a few "arguments" to that. Some of the arguments is based on the fact that we "see" things from bounced light which, in itself, distort what we see. Here are the arguments:
Well, I hope someone can convince me that those scientists have removed/nullified/compensated the effect of light from their experiments. If so, I would like to know how they did it instead of saying that they just did. Personally, I hope I am right: Speed of light is just like speed of sound --- something we can safely exceed if we have the technology. If so, it will open up a lot of possibilities. I am, however, open to suggestions.
Food for thought: What makes you think you have not seen anything that moves faster than speed of light? Do you know how they look like? Do you think those unduplicated and unexplained "blips" or errors on an otherwise perfect experiments that "you can safely ignore" are really errors or ..... (For example, how do you detect a car travelling at 100 KPH with a pellet gun fired at 1 bullet per second perpendicular to the direction of the car's travel at a fixed point on the road? Will you take the bounce of a bullet versus a hundred that went through the air as the desired result or an error?)
Anyway, have fun everyone.
Regards, The Wondering Mind Sept. 7, 2005
Sorry for the double submission. My web page gave me an error when I posted the first one. I did not see the article posted until after I posted the second one.
Regards, The Wondering Mind Sept. 7, 2005
Relative speed of light is less important to the nature of light than the fact that the speed of light is the speed at which the matter that makes up a body has neglidgible ability to react with matter moving at a similar speed (including friction wich would lead to near exact translation), which suggests four things, that any body moving the speed of light is for all purposes light, that light travel would be posible if you could actually slow the speed of light, rather than just refract it in place, and through refraction you would be able to freeze all reaction over an indefinite time a body, the last important difference this would make is proof that actual speeds (speed relative to a stationary point) of greater than light are impossible for the sole reason that they are unable to react in any way that would create further prepulsion.
- Nicho I.
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The following sentence, which appears in the article, is either contradictory in itself, or implies some kind of speed-of-light travel which occurs, but not through space. It needs clarification:
If this is true, an object may travel at the speed of light, but it will not travel through space when this is done, as no time will pass while it is at the speed of light. -- 4.239.0.189 17:56, 23 February 2007 (UTC) If we send a light ray to the moon and wait approximately 2 1/2 seconds, we will receive a returned reflection. So we have existed in a time dimension for a time period we have quantified as 2 1/2 seconds. We then say that the time dimension existing for the moving light ray (and anything associated with it) is reduced to zero, and that it can go anywhere in zero time. This sounds unreasonable, But does involve the more reasonable proposition that there is an interrelationship between our methods of measuring time and space, and that they are not independent of each other. So now we're embroiled in the mathematical intricacies of an interdependent spacetime continuum, without having developed any particular reason why the velocity of light is what it is, or even a willingness to consider that it is the result of some physical process involving a moving particle. WFPM ( talk) 18:05, 17 August 2009 (UTC) |
Last edited at 18:07, 17 August 2009 (UTC). Substituted at 22:04, 3 May 2016 (UTC)