# Thread: Universal Symmetry, Was C Faster In The Past

1. I have been reading about 'fast light' theory that suggests that light travelled faster, than the current C of 299 792 458 metres per second, in the past and that this explains why the extreme edges of our universe appear the same.

If this theory does indeed have merit it suggests that the speed of light has slowed down over time, could this actually be possible?

http://www.newscientist.com/article/...html?full=true

2.

3. This sounds like Jo Magueijo's varying speed of light theory. Is it possible? In a sense, yes. The early universe is often likened to a black hole. People talk of a singularity, and refer to the Big Bang as a "phase change" that resulted in expansion. In that respect a universe expanding over time can be likened to pulling away from a black hole in space. Down near the event horizon the coordinate speed of light, as measured by distant observers, is low - the coordinate speed of light varies in a non-inertial reference frame such as a gravitational field. As you pull away from the event horizon, it increases. You don't notice this locally, you always measure c to be 299,792,458 m/s because you use electromagnetic phenomena to define your second and your metre. However the distant observer who's watching you does notice a difference. But note that this parallel suggests that the speed of light has increased over time, not decreased. So IMHO it could be possible, but in the opposite sense.

4. Thats really interesting, the idea that light is speeding up. That would mean though that if it was slower in the past it can't be an explanation for why both sides of the universe look the same.

5. No, inflation is used as an explanation for that. But think about it for a moment. Imagine that you and I are in a bubble of artistic licence, watching the early universe from the "outside". (There is no outside, but just go with the flow). Imagine it's a ball, and we watch it expanding at a constant rate. Now imagine that the speed of light inside the universe starts off really slow, and gradually increases. Somebody inside the universe wouldn't notice this, just as you don't notice that your local light clock is going slow when you're subject to gravitational time dilation near a black hole. To them it would look as if the constant-rate expansion started off amazingly fast and then slowed down. It would look like the universe enjoyed an initial period of very rapid inflation. And of course, "inflation answers the classic conundrum of the Big Bang cosmology: why does the universe appear flat, homogeneous, and isotropic in accordance with the cosmological principle..." Turning this VSL thing on its head seems to fit better with black holes and the standard model of cosmology.

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