Seven Brief Lessons on Physics

by Carlo Rovelli

gravitational field is not diffused through space; the gravitational field is that space itself. This is the idea of the general theory of relativity. Newton’s “space,” through which things move, and the “gravitational field” are one and the same thing.

the theory describes a colorful and amazing world where universes explode, space collapses into bottomless holes, time sags and slows near a planet, and the unbounded extensions of interstellar space ripple and sway like the surface of the sea

that space and gravitational field are the same thing.

It’s as if God had not designed reality with a line that was heavily scored but just dotted it with a faint outline.

Or does it mean, as it seems to me, that we must accept the idea that reality is only interaction?

To the very last, the desire to challenge oneself and understand more. And to the very last: doubt.

Where are these quanta of space? Nowhere. They are not in space because they are themselves the space. Space is created by the linking of these individual quanta of gravity. Once again, the world seems to be less about objects than about interactive relationships.

The difference between past and future exists only when there is heat. The fundamental phenomenon that distinguishes the future from the past is the fact that heat passes from things that are hotter to things that are colder.

It is not impossible for a hot body to become hotter through contact with a colder one: it is just extremely improbable.

But no one would dream of saying that things “here” exist, whereas things that are not “here” do not exist. So then why do we say that things that are “now” exist and that everything else doesn’t?

“what’s non-apparent is much vaster than what’s apparent.”