There’s a concept that’s crucial to chemistry and physics. It helps explain why physical processes go one way and not the other: why ice melts, why cream spreads in coffee, why air leaks out of a punctured tire. It’s entropy, and it’s notoriously difficult to wrap our heads around. Jeff Phillips gives a crash course on entropy.

Now that you know what entropy is, here’s a t-shirt for you:

[TED Ed | Entropy isn’t what it used to be]