Talk:Speed of light

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Couple of things[edit]

It looks like there's going to be some overlap between this article and Starlight_problem. Also should this really be in the Conservapedia: namespace? -- Stevo (talk) 17:39, 2 July 2007 (CDT)

I'm working on the overlap right now. But yeah, I guess it shouldn't be in the Conservapedia namespace, I'll move it. It's a Conservapedia refutation, but has no bearing on the actual Conservapedia article.-αmεσG 18:16, 2 July 2007 (CDT)
Still seems to be a major overlap.--Bob_M (talk) 10:46, 2 August 2007 (CDT)

Does the overlap matter? As long as both agree and are Xlinked you're just hammering the message home. Keepgerbils(in a cage)! 11:05, 2 August 2007 (CDT)

I think it gets tiresome to see it on 3-4 pages. Mention the issue, and a very brief overview of the "solutions" and rebuttals - if at all - that's what links are for. humanbe in 21:00, 19 September 2007 (EDT)


I think introducing refraction in the first paragraph is a bit strange. I'll try to make a better lower section to deal with it (and diffraction adn reflection). humanbe in 21:00, 19 September 2007 (EDT)


I got redirected here from the "speed of light", uncapped. Proposing to move (back) shortly, pending discussion. The word "light" isnot a proper noun. (I'll do the grunt work) humanbe in 02:40, 6 October 2007 (EDT)

Cherenkov radiation[edit]

Can someone more knowledgeable than me check up for sure what Cherenkov radiation is? I've always been lead to believe that it was emitted when charged particles decelerate. In this article it currently says that it's caused by photons decelerating. Photons aren't charged particles. Are we sure that what it says here is correct? If not then perhaps it should be removed as an example of why the speed of light cannot have changed over time. — Unsigned, by: / talk / contribs

Bunchanumbers seems to be right (Wikipedia) SusanG  ContribsTalk 15:36, 22 July 2008 (EDT)
OK, so what's the protocol around here for doing something about it? Find someone who knows something about it?
[I really must get around to creating an account but other than making the occasional grammatical or punctuation edit this is the first time I've ever contributed anything at all]
You can do it yourself - citations are very helpful, of course. If you chop out a chunk, it would be kind of you to copy and paste it here to talk and explain why. Thanks! ħumanUser talk:Human 16:46, 22 July 2008 (EDT)
[I was Bunchanumbers]. I don't really know enough about the topic to change it. The only thing I could do is remove the reference to Cherenkov radiation as the way it is currently is incorrect. However, I'd imagine that whoever put it there may well have had a reason, even if a slightly confused one. The lack of Cherenkov radiation really may be a refutation of the idea that c is changing, just not for the reasons given. — Unsigned, by: Weirdbeard / talk / contribs
Hence the reason to cut and paste it here - it's out of the article while in doubt, but here while we figure out what to do with it longterm. ħumanUser talk:Human 17:20, 22 July 2008 (EDT)
OK. I've commented it out for the moment. Here's what it says (it's in the section headed 'The Starlight Problem' as the first entry in the list of reasons explaining why the speed of light can't have significantly changed):
  • First, it is empirically disproven. If the speed of light had changed in any remarkable way, there would be evidence of photon deceleration. When a photon decelerates, as in, when it passes into a new, slower medium and must shed its higher energy, it emits Cherenkov radiation. If the entire universe had decelerated, we would expect to see, for several light-years, massive Cherenkov radiation. We see no such thing. Weirdbeard 17:57, 22 July 2008 (EDT)

Rejection of Speed of Light[edit]

Based on the list of pseudosciences page, I created an article about faster than light travel. Then, I realized that it is covered by this article. How should I handle it? EricB 10:37, 24 July 2008 (EDT)

What's it called? Can it stand alone if more is added? ħumanUser talk:Human 14:00, 24 July 2008 (EDT)
It is called Faster-than-light travel. It is in a very preliminary stage. I stopped editing it when I realized there was this page. There is nothing new currently on the page. Therefore, we should probably just delete it.
You could make it a redirect to this article, also. Whatever you feel makes the most sense. ħumanUser talk:Human 17:17, 24 July 2008 (EDT)

The Thought Experiment[edit]

The Thought Experiment doesn't make sense to me. Alice can see the oscillating waves. So how does Bob not being able to see them make them not exist? Bob is traveling the same speed as the light, so the waves appear static. Alice is not, so she sees them oscillating. I cannot understand how Bob not being able to see them makes them not exist; actually, the fact that he doesn't see them oscillating seems to make perfect sense to me because he's travelling at the same speed as the oscillations. We should edit for clarity or else delete the Thought Experiment if it doesn't make sense. (talk) 05:14, 4 April 2011 (UTC) 3.Apr.'11

IANAP, but I think the point is that light appears because of waves; no waves => no light. Since Bob sees no waves, Bob has no light. But the light is there. =><= Maybe? That being said, I don't think this is the greatest example out there. ThunderkatzHo! 05:57, 4 April 2011 (UTC)
There are various problems with this example. First if only works if you assume that light is made of waves rather than particles (photons). Secondly we "see" light if it hits us in the eye. The example has Bob travelling edge-on to the light and there is no way he could "see" it anyway. Finally, even if it were all true, why should it prove the point it's trying to prove?--BobSpring is sprung! 07:08, 4 April 2011 (UTC)
I deleted it. :P (talk) 05:28, 7 April 2011 (UTC)
Please stop deleting what you don't understand. ħumanUser talk:Human 08:08, 7 April 2011 (UTC)
If this is the thought experiment I think it is, I always thought the point was that Maxwell's equations break down for an observer at the speed of light, since c=0. Special relativity solves this issue, by preventing any observer from reaching c, and thus Maxwell's equations breaking down in this way. It's not about what a light wave would "look like" in a quotidian sense, simply what it would "look like" from the viewpoint of mathematical physics. (But maybe I am remembering this stuff wrong, I am not an expert in this area...) --(((Zack Martin))) 08:26, 7 April 2011 (UTC)
Please use an example that makes sense or edit the example to make sense. It's not that I'm stupid to not understand the example, it's that the example is not presented understandably. Alice sees the light. Bob does not. The example goes on to conclude "Bob does not see the light therefore it does not exist". This is not logical. Alice sees the light. Does the light exist in Alice's experience and not in Bob's? Is Alice having visual halluncinations? Does Bob and/or Alice exist only as much as the light exists? I won't delete it anymore, but please fix it. (talk) 08:50, 7 April 2011 (UTC)
Existence doesn't happen until there's a mind to experience it, so the fact that light exists for Alice and not for Bob does not prove that "Bob cannot travel at the speed of light" at all. We are talking about the perception of a lightwave, not the physical reality of the lightwave itself. If Alice turned 180º away from the lightsource in a vacuum, she would therefore see no oscillating waves either, does that mean the light does not exist or that Alice does not exist or what? It means that she perceives no light. Just as Bob perceives no light, due to oscillating at the same speed as the lightwaves; in this way, Bob could be traveling directly at the lightsource rather than parallel to it and still see no light. The example does not prove what it sets out to prove. (talk) 01:33, 16 April 2011 (UTC)
Oh, IP, you say Existence doesn't happen until there's a mind to experience it - have I met a fellow idealist? Please, make yourself an account. It would be nice to have some more idealists on this site, I feel quite lonely... --(((Zack Martin))) 01:39, 16 April 2011 (UTC)
There, now I have an account. I don't know if I'm an "ideal-ist," per se, but I do think that if a tree fell in the forest and nothing was there to hear it, then it would not make a sound, because a sound is not just a vibration through a medium or media, but also an ear and a brain and a nerve and a consciousness. Künstlerin (talk) 07:41, 27 April 2011 (UTC)
So, do stars not give off light unless they're being looked at? 07:48, 27 April 2011 (UTC) C®ackeЯ
@Kunstlerin "because a sound is not just a vibration through a medium or media, but also an ear and a brain and a nerve and a consciousness" Well sure, if you define a sound as requiring a brain then it does, but you are just begging the question. I'm not sure that I would choose such a definition. DamoHi 09:47, 27 April 2011 (UTC)
@cracker, maybe. ...right? ... @Damo, yeah ur right... i should have said a "mind" - not necessarily a "brain" ... but anyways, im just thinking, like from a rational perspective, every concept is a "meme," yeah? Sound, too. Although sound is also "real" (in that it has physical properties), the "concept" of sound is a mental construction. The physical properties in-and-of-themselves are not what "sound" is, sound is the meme that a mind constructs or reifies to systematize or "describe-with-language" vibrational information perception. Künstlerin (talk) 08:31, 30 April 2011 (UTC)
because a sound is not just a vibration through a medium or media Only because you're defining it thusly. But the concept of "just a vibration through a medium or media" has to exist as well, and a tree falling in a forest with no one around still produces such vibration, regardless of if it is "sound" by your definition. (Yes, Maratrean, I'm assuming materialism.) --Eira OMTG! The Goat be Praised. 10:56, 14 May 2011 (UTC)
ackk, this is so off the point... the thing is, i still question the logic of the thought experiment. it doesn't matter about experience or brains or minds or anything. just the facts presented in the lead up to the conclusion don't add up to the supposed conclusion. why can't alice see light and bob not see light????? why is that so impossible? even from the "perspective of mathematics" or whatever?? Künstlerin (talk) 06:50, 14 May 2011 (UTC)

The Thought Experiment should be disregarded by analogy. Replace Alice with left-handed particles, and Bob with right-handed particles, and the light beam with W and Z bosons. Alice can interact with the particles, and Bob cannot. That does not create a contradiction, and in fact, this is the very way that the world is understood to work at this time. Thus the argument format itself is invalid. --Eira OMTG! The Goat be Praised. 10:45, 14 May 2011 (UTC)

I'm glad it has gone. A thought experiment should clarify things for the reader, but if it simply leaves the reader confused then it has not fulfilled its purpose. Even if it were 100% valid (which I don't think it is) if it ended up using an explanation which is more confusing than the thing it is trying to explain then it has failed.--BobSpring is sprung! 12:01, 14 May 2011 (UTC)
I could rewrite it the same way Marcus Chown puts it. ADK...I'll riot your cob! 08:57, 15 May 2011 (UTC)

Woo Contingent and Psychic Phenomena[edit]

To see what I'm talking about about people asking if the neutrino FTL result could mean psychic phenomena exist, scroll down the reference I provided to the discussion section and look for comments by Guthrie Prentice.— Unsigned, by: / talk / contribs

Neutrinos in 2012 - update[edit]

We probably need to update in the light of of this and this. But I'm pushed for time. --BobSpring is sprung! 08:16, 17 March 2012 (UTC)

I'm doing something now. Peter horas non numero nisi serenas 08:23, 17 March 2012 (UTC)

Speed of light not so constant after all[edit]

It looks as though light speed could change given right conditions.--Spinoza enthusiast (talk) 21:37, 28 February 2017 (UTC)