Carlo Rovelli Quotes

General relativity has changed our understanding of space and time. ...The spacetime of general relativity ...is likely to be just a classical approximation that loses its meaning in the quantum theory, for the same reason the trajectory of a particle does.

In his youth Albert Einstein spent a year loafing aim- lessly. You don’t get anywhere by not ‘wasting’ time – something, unfortunately, which the parents of teenagers tend frequently to forget.

What makes the difference is the mass. ...[T]he earth is a big mass and it slows down time. If you go to a bigger mass, like Jupiter, it's stronger. If you go near a big star it's stronger. If you're near a black hole... it's even more strong, so strong that if you go very near... time essentially stops down. It goes very, very, very slowly.

[I]n a fundamental description of nature we must "forget time"... this can be done in the classical and in the quantum theory.

I argue that the best strategy for understanding quantum gravity is to build a picture of the physical world where the notion of time plays no role at all.

Hawking was one of the good physicists of his generation, not the universal genius the popular press has depicted. It is a pity, because this confusion fogs the memory of a remarkable man.

Quite remarkably, this was understood before having good clocks... It is one of great intuitions by Einstein. In 1915 he completed the theory of relativity... At the time clocks were not good enough... it was a theory, a good speculation... Today it is not a theory... It's a fact that we measure in the labaratory. ...It's so clear and definite that technology needs this to be taken into account.

Intuitively (and imprecisely) speaking, time "flows", we can never "go back in time", we remember the past but not the future, and so on. Where do all these very peculiar features of the time variable come from? ...[T]hese features... emerge at the thermodynamical level. ...[T]hese are all features that emerge when we give an approximate statistical description of a system with a large number of .

The way evolution is treated in general relativity, is... subtle... Change is not described as evolution of physical variables as a function of a preferred independent observable time variable. Instead, it is described in terms of a functional relation among equal footing variables... as... (T₁,T₂)... In general relativity, there isn’t a preferred and observable quantity that plays the role of independent parameter of the evolution... General relativity describes the relative evolution of observable quantities, not the evolution of quantities as functions of a preferred one. ...[w]ith general relativity we have understood that the Newtonian "big clock" ticking away the "true universal time" is not there.

But it isn’t absence that causes sorrow. It is affection and love. Without affection, without love, such absences would cause us no pain. For this reason, even the pain caused by absence is, in the end, something good and even beautiful, because it feeds on that which gives meaning to life.

In the elementary equations of the world, the arrow of time appears only where there is heat. The link between time and heat is... fundamental: every time a difference is manifested between the past and the future, heat is involved.

Children grow up and discover that the world is not as it seemed within the four walls of their homes. Humankind as a whole does the same.

An overly pragmatic attitude is not productive in the long run.

The idea that a well-defined now exists throughout the universe is an illusion, an illegitimate extrapolation of our own experience

The World is Made of Events, not Things.