Generalisation

[skulldude]

One of the main concepts of Special theory of relativity is that

 

The velocity of light is a constant in all frames of reference. This concept includes the entire universe.

 

But we havenot even explored 10% of the universe.

 

Then how is it that we can generalise this law to the whole universe. Doesnot it look arbirary.

[timo]

The assumptions that nature's laws are the same everywhere in the universe is one of the most fundamental assumptions for cosmology (they even go a step further and for practical purposes often assume that the universe looks the same everywhere). I am not sure if I would call it arbitrary. It is a choice and there is no proof that the choice is correct, yes. But that is true for other common choices in science, too. Some assumptions are simply an integral part of a scientific field.

 

Not exactly what you talk about but related (assuming identity in time rather than space):

One of the most basic assumptions in science, particularly physics, is that one you (experimentally) found some rule to apply to some situation you assume that it will also apply next time. Like: For the last 1000 years apples fell to the ground, therefore apples will fall to the ground in the future.

This assumptions seems obvious (I claim that is because it is how human learning works) but that is no reason for correctness - in fact "seems obvious" is often an "erroneous content here"-sign. The approach also has lead to great successes in the past - but taking this as an argument is self-referencing.

 

I do not know what the philosophers' answer to the problem is but afaik there is a whole branch of philosophy ("Epistemology", according to Wikipedia-translation) dedicated to the question what you can really know. At least in physics at some point you simply have to assume things to come to conclusions. For me that is also a strong argument to consider science as something that should ultimately lead to applications - an attitude that most of my colleagues do not share, as far as I know.

[GDG]

We assume that the universe and its laws are the same in all directions and all locations because there is no reason (in general) to assume otherwise.

 

Sure, it is possible that the speed of light is different in another part of the universe, but unless (a) you have a theory that relies on or explains it, and (b) you have some experiment that could distinguish the different possible results, scientists will rely on the simplest theory that fits the facts.

[skulldude]

Thanks mates

[ajb]

Dirac was one of the first to think about the idea that physical constants can change over time. I think his primary interest was in the idea that Newton's constant decays as time goes on, explaining the relative weakness of gravity.

 

I know that John Barrow [1] and Jean-Pierre Petit [2] and I am sure many others have looked at cosmologies with varying light-speed. This is outside my real expertise, so I suggest a search on the ArXiv.

 

 

So, if your question is "has anybody thought about variable light-speed?", the answer is yes.

 

 

 

References

 

[1] @Article{Barrow:1998eh,

author = "Barrow, John D.",

title = "{Cosmologies with Varying Light-Speed}",

year = "1998",

eprint = "astro-ph/9811022",

archivePrefix = "arXiv",

SLACcitation = "%%CITATION = ASTRO-PH/9811022;%%"

}

 

 

[2] @Article{Petit:1988ti,

author = "Petit, J. P.",

title = "{AN INTERPRETATION OF COSMOLOGICAL MODEL WITH VARIABLE

LIGHT VELOCITY}",

journal = "Mod. Phys. Lett.",

volume = "A3",

year = "1988",

pages = "1527-1532",

doi = "10.1142/S0217732388001823",

SLACcitation = "%%CITATION = MPLAE,A3,1527;%%"

}