Seven Brief Lessons on Physics

by Carlo Rovelli

A handful of elementary ingredients that act like bricks in a gigantic Lego set, and with which the entire material reality surrounding us is constructed. The nature of these particles, and the way they move, is described by quantum mechanics.

everything that exists is never stable and is nothing but a jump from one interaction

Heat, as we know, always moves from hot things to cold.

In every case in which heat exchange does not occur, or when the heat exchanged is negligible, we see that the future behaves exactly like the past.

motion of the planets of the solar system heat is almost irrelevant, and in fact this same motion could equally take place in reverse without any law of physics being infringed.

But if there is friction, then the pendulum heats its supports slightly, loses energy, and slows down. Friction produces heat. And immediately we are able to distinguish the future (toward which the pendulum slows) from the past. We have never seen a pendulum start swinging from a stationary position, with its movement initiated by the energy obtained by absorbing heat from its supports.