# Fermi Paradox. What am I missing? **URL:** \ **Category:** Factual Questions\ **Created:** [January 11, 2019, 8:05pm UTC](https://boards.straightdope.com/t/fermi-paradox-what-am-i-missing/827614 "2019-01-11T20:05:32Z")\ **Posts on this page:** 1\ **Showing post:** 123
**Author:** ![septimus](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/septimus/32/410_2.png) [@septimus](https://boards.straightdope.com/u/septimus)\ **Post date:** [January 24, 2019, 9:07pm UTC](https://boards.straightdope.com/t/fermi-paradox-what-am-i-missing/827614/123 "2019-01-24T21:07:18Z")
Much discussion about the arrow of causality uses circular reasoning. > [@rat\_avatar](#): > > The _thermodynamic arrow of time_ is the the core asymmetry. The second law of thermodynamics is not time-reversible and entropy has far more to do with free energy than the typical description of “disorder” that is used for Entropy. It seems to me that once you link the arrow of causality to the thermodynamic arrow, you’ve given up on an “absolute” arrow. _ **Stephen Hawking once thought that time’s arrow would reverse** _ during a contraction to the Big Crunch. Although he may have revised this opinion, the fact that he once believed it makes one skeptical of overly-glib refutations. (And he revised his opinion not out of a belief in a fundamental Time’s Arrow but because his calculations showed him entropy would continue to increase during the contraction.) The Second Law is closely related to the Law of Large Numbers — a container with trillions of molecules will move toward equilibrium. But what if the container has only 2 or 3 molecules? It’s almost as likely to lose entropy as to gain entropy. If it loses entropy for a few seconds, would you say that its local arrow of time reversed? --- _[View the full topic](https://boards.straightdope.com/t/fermi-paradox-what-am-i-missing/827614)._