Seven Brief Lessons on Physics

by Carlo Rovelli

The sun bends space around itself, and Earth does not turn around it because of a mysterious force but because it is racing directly in a space that inclines, like a marble that rolls in a funnel. There are no mysterious forces generated at the center of the funnel; it is the curved nature of the walls that causes the marble to roll. Planets circle around the sun, and things fall, because space curves.

A physicist is only too happy when he finds a conflict of this kind between successful theories: it’s an extraordinary opportunity.