# entropy-infomartion correlation at preliminary universe?

according to the theory of cosmic inflation after Alan Guth, the information should have travelled 100 times the speed of light at the very beginning after the big bang.

-when we talk about information what do we mean exactly by information ? -how could these information have travelled 100 times the speed of light, where "c" according to the general relativity should be constant at every reference ?

many thanks

## 2 Answers

I think you misinterpreted the quote. Here it is in full:

To explain, for example, how the universe could have smoothed itself out to achieve the uniformity of temperature that we observe today in the cosmic background radiation, one finds that in the context of the standard Big Bang theory, it would be necessary for energy and information to be transmitted across the universe at about a hundred times the speed of light.

In a nutshell, the universe is isotropic and homogenous - it's basically the same on large scales - and the cosmic microwave background appears to be uniform. In the original Big Bang model, information would have to have been transmitted faster than light.

Inflation solves that problem - indeed, the idea that the entire universe would somehow have been in causal contact was one of the reasons Guth proposed inflation in the first place!

Inflation is not the source of this problem; it is the solution.

The speed of light is constant relative to the fabric of space, but when space itself is expanding, the speed of lighg, as measures by an external obsrver can be larger than c. This is a known fact in general relativity (special relativity doesnt consider such possibility).

Update: what has slowed down was the expansion of space itself, with drags the light with him . So the reduction in the speed of light is only apparent. It was always c relative to the space itself. An intuitive visualization is if you have an ant walking at constant speed on an elastic rope. If the rope expands, the the speed of the ant as measures from another person on the rope will increase, this is because there is more rope created beteween the observer (which could be represented my a marck on the rope), and the ant. Even if the ant were at rest relative to the rope, the opbserver would still see it moving at the rope expansion rate.

• Special relativity was a typo...but i'm still not convinced about why then universe slowed down the "c"? Dec 3, 2014 at 1:10