Why can you remember the past but not the future? Why does a broken cup never reassemble itself? The answer lies in one of the deepest and most reliable laws in all of physics — the second law of thermodynamics — and a slippery idea called entropy. We explain what entropy really is, why it always increases, and how it gives time its one-way direction.

You'll come away understanding what entropy actually measures, why the second law is really about probability rather than mystery, how this single principle explains the "arrow of time," and why life itself doesn't break the rule.

Talking Science is sponsored by Kinsoft. Visit www.kinsoft.com.au

Further reading: Sean Carroll's From Eternity to Here; the Feynman Lectures on Physics, Volume I, on thermody ...