[hannasanarion]

The universe is by definition a closed system. The universe is all that exists, if there is something that could have an effect on it, it would be part of the universe.

The universe is expanding, distances are getting bigger, and there is no reason to think that it'll suddenly decide to stop and get small again.

Balloon theory was blown up by the discovery of an increasing cosmological constant (aka dark energy).

Once a fire has burned to ash, you can't turn it back into wood again. Cyclical time is wishful thinking, contradicted by all evidence.

[posterboy]

You are making the mistaking of supposing you conclusion as hypothesis, don't you. Because:

> The universe is by definition a closed system.

There is no de-finit-ion, that's my hole point (excuse the pun, it fits better than any other time)

> The universe is all that exists, if there is something that could have an effect on it, it would be part of the universe.

Yes sure, but what if it's endless? That's not closed in the sense of thermodynamics I don't think.

To conclude from your statement, that the universe is a closed system, kind of requires to presume universal entropy increase, in case of infinity. I can't do the maths though, so I might be wrong. It's just a hunch.

> The universe is expanding, distances are getting bigger,

The visible ...

background radiation may invite inference, but really you get interference.

> and there is no reason to think that it'll suddenly decide to stop and get small again.

In a e.g. 10^50 years would not exactly be suddenly

> Once a fire has burned to ash, you can't turn it back into wood again. Cyclical time is wishful thinking, contradicted by all evidence.

I don't disagree.