I Can the information of the whole universe change?

[friend]

They say that the universe started with low entropy, which is a certain amount of information. But I wonder how the information associated with the whole universe can change. By definition nothing can ever leaves or enters the universe as a whole. And if nothing ever enters or leaves a system, then where does the source of increase in information or entropy come from?

 

[phyzguy]

I think the answer is that the universe is governed by quantum mechanics, and quantum mechanics is not deterministic, but inherently probabilistic. Every quantum interaction has a set of possibilities, but eventually only one is realized. Every time this happens, information is added to the universe as a whole.

 

[friend]

Aren't there quantum processes that have an infinite number of possible outcomes, like exactly where a particle strikes a screen in a two slit experiment? What's the entropy of those kinds of processes where the likelihood of one outcome is infinitesimal? Then multiply that by every interaction in the universe.

 

[stoomart]

By definition nothing can ever leaves or enters the universe as a whole.

I don't think entropy and information are things, they're more like metadata about events that can occur (entropy) or have occurred (information).

See Wikipedia's article Entropy (arrow of time):

Entropy is the only quantity in the physical sciences (apart from certain rare interactions in particle physics; see below) that requires a particular direction for time, sometimes called an arrow of time. As one goes "forward" in time, the second law of thermodynamics says, the entropy of an isolated system can increase, but not decrease.

If the universe is not an isolated system as proposed in Loop quantum cosmology, then things may be leaving it through black holes.