Entropy

In A Brief History of Time by Stephen Hawking, there is a part where a teacup falls off the table and smashes on the floor.

Hawking says this:

"Where does the difference between the past and the future come from? The laws of science do not distinguish between the past and the future. Yet there is a big difference between the past and the future in ordinary life.

You may see a cup fall off of a table and break into pieces on the floor. But you will never see the cup gather itself back together and jump back on the table."

"The increase of disorder or entropy is what distinguishes the past from the future, giving time a direction."

Hawking had once believed the universe would stop expanding and would shrink again, and entropy might reverse itself.

Hawking later said that he had been mistaken.