Talk:Speed of light

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Fundamental basis for understanding the speed of light

We should actually talk about the slowness of matter, not the speed of light. From the perspective of light, there is no time, and it takes just as long to reach any point in the universe. In other words, to light, the universe is infinitely small. As you approach the speed of light, ironically it would appear that the stationery matter around you is speeding up. As a matter of fact - when light travels, by definition it travels through time from an earthling observer's perspective. In this view, what is light in a stationary state? Is a better definition for light not matter that is travelling through time? Ie. matter can not travel at the speed of light unless it is converted into photons or "matter travelling through time" - User:Tunasashimi 196.215.118.171 (talk) 23:50, 23 November 2010 (UTC)

In Arthur Eddington's 'Space, Time and Gravitation', he proposed a model in which time is not uniformly distributed in space. In this model, a point B one light year distant from A is also one year ahead in time. As a result, a wave propagated instantaneously from A to B is observed to arrive one year later. Since it would not be possible to be faster than instantaneous, the observed speed of the wave can't exceed 'c'. The time differential would be based on a local frame of reference, so for a wave reflecting from a mirror at B, A is now one year ahead of B, and the round trip appears to take two years. This model accounted for the fact that a particle with mass requires infinite energy to be accelerated to the velocity of light, since the 'real' velocity of the particle would be infinite in order to appear to move with the velocity of light. It would also account for the observation that 'c' is constant regardless of the velocity of the source.96.54.32.44 (talk) 23:51, 30 November 2010 (UTC)

This view makes much more sense, I think it should be taught and covered more widely. - User:Tunasashimi

The point you make is covered by one of the notes, which mentions that the one-way speed of light is arbitrary, and varies according to the convention used to synchronise distant clocks. As you (and Eddington) point out, the one-way speed of light can be considered infinite with an appropriate clock synchronisation scheme. On the other hand the two-way speed of light (say to a mirror and back again) can be measured using just one clock. The currently used convention is to make the one-way speed equal to the two-way speed (Einstein synchronisation) but this is not the only way of doing things. See One-way speed of light. Martin Hogbin (talk) 18:37, 1 December 2010 (UTC)

Interesting indeed - No reference/easily understandable mention of this in the article either! User:Tunasashimi

Overwhelming Evidence

There is so much overwhelming evidence cited here that the speed of light is an absolute limit, that I can't help but think that the "speed of light" limit can't possibly be true. Usually human beings pile up overwhelming evidence when deep down they don't believe something and have to convince themselves otherwise.

98.245.150.162 (talk) 23:56, 22 November 2010 (UTC)

Expansion VS SOL Limit

Is there any possible way, that someone could put together a nice addition for the front page on how the Universe is expanding faster than the speed of light? I think this information should be shown in greater detail because it shows a very big flaw in the argument that the Speed of Light is absolute.

Thank you. —Preceding unsigned comment added by 68.96.242.243 (talk) 01:49, 13 February 2011 (UTC)

FAC nomination

I've nominated this article for Feature Article status today. Please note that user:SandyGeorgia has asked that the other major contributors co-nominate. I suppose this means user:Martin Hogbin and user:A. di M.. (Although see probably was also referring to Brews, not knowing that he is banned.TimothyRias (talk) 16:36, 6 December 2010 (UTC)

I'll try to give feedback over the week-end. I stayed out of this article for the last year and a half so I would be able to review it impartially. Headbomb {talk / contribs / physics / books} 00:05, 10 December 2010 (UTC)

I have also kept a low profile on this article since the arbcom case. If you need me to do anything please let me know what you want. Martin Hogbin (talk) 18:21, 11 December 2010 (UTC)

Martin: You were a very major contributor, qualitatively as well as qualitatively, and a lot of your content remains in the article. You deserve to be proud of your contributions, and there is no reason whatever for you to keep a low profile. The arbitration solved a problem, and that problem was not you.—Finell 11:53, 15 December 2010 (UTC)

Good work and good luck with the FA. I strongly support it. I have four minor concerns that I feel should be looked at by someone more acquainted with the article then me. None of these are important enough to affect FA, in my opinion but are nice to have.

1. The lead is too fat with detail. The most blatant example is the use of an example in the lead. But every paragraph has at least one sentence that can be removed.
2. (nitpick) I don't think that Einstein was motivated by the 'lack of evidence of ether'. He seemed to think the theory was sufficient, iirc.
3. The 'Upper limits on speed' section needs a rewrite (and/or a different diagram). It is confusing.
4. Cavity resonance is an example of interference and therefore should properly be placed after the interference and include a note that it is a type of interference.

Again good work. TStein (talk) 18:32, 15 December 2010 (UTC)

"Practical effects" -> Astronomy

I don't believe that the "Astronomy" section should be under the "practical effects" section. A "practical effect" is something that changes something that occurs in everyday life. Saying B is a practical effect of A, when B and A are both abstract sciences, seems to be a bit of a non-sequitur. Magog the Ogre (talk) 19:49, 10 December 2010 (UTC)

But nor A, nor B are abstract sciences here. A is "the fact that the speed of light is finite", and B is "the fact that we (i.e. astromers) use A to infer the evolution of stars and galaxies". I think that B qualifies as a "Practical effect" of A, or even better as a "Practical consequence", or, if you like, as a "Useful consequence", or as a "Useful effect", or as a "Useful application". I don't object to changing that section header, but I do object your removal of the astronomy subsection, so I fully agree with Physchim62's revert. DVdm (talk) 20:50, 10 December 2010 (UTC)

Wikt:practical: "Being likely to be effective and applicable to a real situation; able to be put to use." I cannot fathom how Astronomy fits that definition, or will fit that definition until humanity gains an advantage from it aside from the theoretical (theory being the antonym). I would much prefer a section on the relationship between energy and mass; e.g., "were c twice as fast, then every energy reaction would involve four times as much energy, greatly altering existence as we know it. Even a small change in c would cause large changes - for example in how cells function." Magog the Ogre (talk) 04:04, 11 December 2010 (UTC)

But, the finiteness of the speed of light is indeed "likely to be effective and applicable to a real situation", namely to the creation of theories about stellar and galactic evolution. What you propose is not related in any way to (1) the finiteness of the speed of light, nor (2) to the point that is made in the current Astronomy section. DVdm (talk) 11:30, 11 December 2010 (UTC)

Would "Consequences and applications of finiteness" cover the entire section adequately (for all practical purposes)? Hertz1888 (talk) 04:24, 11 December 2010 (UTC)

Fine with me. Webster lists the following synonyms of practical: actionable, applicable, applicative, applied, functional, practicable, serviceable, ultrapractical, usable (also useable), useful, workable, working. Useful is there, applicable is there... — it's a all there, in fact. DVdm (talk) 11:30, 11 December 2010 (UTC)

I guess this is what happens when you come to a page frequented by science geeks (not an insult: I'm one too). The ability to measure a distant star is considered "practical" on the same level as everyday usage of a computer or a GPS. Magog the Ogre (talk) 21:20, 15 December 2010 (UTC)

Upper limit on speeds

The section "Upper limit on speeds" says "According to special relativity, the energy of an object with rest mass m and speed v is given by γmc²". Shouldn't the "c" be a "v"? It talks about velocity approaching the speed of light in the following text.

I remember very little about physics, so I don't feel right correcting formulas I don't know anything about. However, the text around that formula seems to indicate that it is wrong.

Cowgod14 (talk) 18:32, 22 December 2010 (UTC)

Nope. For small v, γ ≈ 1 + v²/2c² so E ≈ mc² + mv²/2 i.e. the rest energy plus the non-relativistic kinetic energy. A. di M. (talk) 18:56, 22 December 2010 (UTC)

FA

Congratulations, and thanks, to all of you who helped to win back this article's star. It definitely deserves that honor now.—Finell 00:44, 25 December 2010 (UTC)

Speculative interpretation or a religious text, not a scientific result at all.

Wouldn't [1] have helped readers realize the mention of Speed of Sun-light being clearly present accurately in the 1300's? Again I wanted to know why one cannot cite quotations from the religious texts?Ganesh J. Acharya (talk) 05:39, 21 February 2011 (UTC)

I had cited the following

Sayan. a (c. 1315-1387) while commenting on Rigveda stated "tatha ca smaryate yojananam. sahasre dve dve sate dve ca yojane ekena nimis.ardhena kramaman. a namo stu ta iti" which when translated is [O Sun,] bow to you, you who traverse 2,202 yojanas in half a nimesa", this speed turns out to be 186,413.22 miles per second which being near to the speed of light, is speculated to be speed of light it self. Src: http://www.ece.lsu.edu/kak/sayana.pdf, (accessed 15 Feb 2011), the referenced information is accessed from Indian Journal of History of Science, vol. 33, 1998, pp. 31-3 Ganesh J. Acharya (talk) 05:41, 21 February 2011 (UTC)

That sources doesn't appear to me to be claiming that they knew or estimated the speed of light, just that there was a numerological coincidence and some astronomy traditions that were lost and worth investigating. Dicklyon (talk) 06:40, 21 February 2011 (UTC)

Yes, out of who knows how many big numbers in historic texts it's one that can be made close to the speed of light. But it's not an estimate or calculation of the speed of light, and making that connection is pure speculation by the writers of that paper, relying on unconvincing assumptions about the precise sizes of the units involved.--JohnBlackburne^words_deeds 10:44, 21 February 2011 (UTC)

ok, again the reference is talking about "speed of light" and may be they are speculating. But then as per what guidelines of wikipedia it should not be included. Ganesh J. Acharya (talk) 06:11, 22 February 2011 (UTC)

The reference is actually arguing that Sayana is in all likelihood not referring to the speed of light , but to the speed of the Sun as it transverses the sky. This makes the interpretation of this text off-topic in this article. More so, since, whatever what was meant, this phrase seems to have had no influence on the historical development of the subject. Inserting a phrase like "some scholars have suggested that some phrase in the Sarayana may be interpreted as giving a value of the speed of light" would give undue weight to a singular interpretation of a religious text.TR 08:57, 22 February 2011 (UTC)

I agree, this text is not appropriate here. Martin Hogbin (talk) 09:24, 22 February 2011 (UTC)

• Is sun-light part of sun? even if it is written sun in travelling, is it wrong?
• Currently we could have a preconceived mindset that sun and its light are different. Why do we see them different?
• If I blow a balloon, does the balloon travel while it expands, or it does not travel?Ganesh J. Acharya (talk) 12:59, 22 February 2011 (UTC)

I don't see how the speed at which the sun transverses the sky, and the speed of the light travelling from the sun to us could be seen as the same thing, especially since the two are perpendicular. Nor do I see how it is relevant to discuss that on this page, since it has nothing to do with improving the "speed of light" article.TR 13:08, 22 February 2011 (UTC)

Rounded speeds

What is the point in having speeds rounded to 1 significant figure? Surely it would be better to have them to at least 3 or 4? I tried doing this but my edits were reverted on the grounds that it was intentional. Xtremerandomness (talk) 23:17, 22 February 2011 (UTC)

The article gives both extremely accurate figures and, in the "Approximate values" section, rounded ones that will be convenient and sufficient for many readers and casual purposes. Hertz1888 (talk) 23:31, 22 February 2011 (UTC)

People are perfectly capable of rounding figures to one or two significant figures in their heads. It's far easier for the majority to do that than to make the few looking for a more accurate figure have to delve through the article at large. Xtremerandomness (talk) 23:33, 22 February 2011 (UTC)

In my experience, that's not so true. Most people who have grown up since the demise of slide rules are relatively clueless about significant figures, and get distracted by digit values as if they mean something more than they do. The conventional rounded values are what we should be using in contexts where simple info is appropriate; the more-exact or exact numbers have their place, too. Dicklyon (talk) 04:23, 23 February 2011 (UTC)

I would disagree with you on that one - almost all people understand that these values are best rounded to 1 or 2 significant figures in most instances, even if they wouldn't know what a "significant figure" was if it was mentioned in conversation. Why not include 'metres per second' in the 'approximate values' section for the ease of others too? It is inconsistent not to do so. This is on top of the fact that it is not fair to patronise the community, presuming that they are unable to work out for themselves what is useful, whilst telling those that do need the more accurate information that they have to search through the article. I couldn't find them all in one place, so for some it would be quite a pain for them to have to do so. Xtremerandomness (talk) 14:06, 23 February 2011 (UTC)

299,792,458 is 300 million when rounded to three significant figures. --137.43.105.17 (talk)