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Comment by RivieraKid | Hacker News Reader

> The speed of light does not vary with time or place.

That's just an assumption.

If we take relativity at face value, the speed of light is c = 2.997 x 10^8 <<<locally>>>. <<<Globally>>> the speed of light can be anything. Cosmologists talk about the universe expanding faster than light during the inflationary phase, which sounds confusing because we're told nothing can move faster than light. While it is true that the speed of light must propogate at only one velocity for all freely moving frames of reference, the speed at which space itself expands can be anything! Relativity does not restrict the speed at which space itself expands or contracts. TL;DR The maximum local speed of anything moving through space in a freely moving frame of reference is c. The speed at which space itself expands or contracts is not limited in any way by Einstein's theory and is consistent with observations of the the inflationary universe in which the universe expanded at faster than the speed of light.

Also, the speed of light in a different part of the universe could be different.

I like to think of it as the speed of information. The quickest any information can move from point A to point B is c. (Even if those points are themselves moving.)

The universe can expand faster than c because there is not actually any information moving between the center and the perimeter.

> > The speed of light does not vary with time or place.

> That's just an assumption.

Supported by evidence. (And no counter-evidence is known.)

> Supported by evidence. (And no counter-evidence is known.)

That was true for Newtonian mechanics for a long time too.

Not for very long. There were things unexplained by Newton starting the first day, right?

There is plenty of evidence, but it would require to change some of our cosmological models (so it's not without controversy). A physicist that has explored the issue in detail is Joao Magueijo:

https://en.wikipedia.org/wiki/Jo%C3%A3o_Magueijo

For a good review of the VSL Theories (Varying Speed of Light Theories) and the evidence behind them see http://arxiv.org/abs/astro-ph/0305457

> There is plenty of evidence

According to your second link: "The evidence is currently slim".

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