Carlo Rovelli Quotes

Whatever the statistical state ρ is, there exists always a variable t_ρ, measured by the thermal clock, with respect to which the system is in equilibrium and physics is the same as in the conventional nonrelativistic statistical case!
This observation leads us to the following hypothesis.

... theoretical physics is less clean than the way it's usually solved. You can always change parameters and save yourself. ... it's very rare that theories are ruled out by just an experiment or a group of experiments. Theories usually come with flexibility. Theoreticians can add flexibility. And so new experiments — you can just patch up your theory.

The new coherent picture is not yet available. With all their immense empirical success, G(eneral)R(elativity) and Q(uantum)M(echanics) have left us with an understanding of the physical world which is unclear and badly fragmented. At the foundations of physics there is today confusion and incoherence.

I am aware that ...[this] answer ...is only one among many possibilities. Other authors have argued that the notion of time is irreducible... Until our theoretical and experimental investigations tell us otherwise... what is important is to put the alternatives clearly on the table...

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 .

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

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.

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

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.

The notion of time familiar to us may... be reconstructed in special physical situations, or within an approximation, as... the "surface of a liquid" disappears ...[at] the atomic level, or "temperature" ...makes sense only in certain physical situations and when there are enough degrees of freedom.

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... interpret mechanics as a theory of relations between variables, rather than the theory of the evolution of variables in time.

[T]ime is much more elastic than our intuition of this rigid passage... The time interval between one point and another... depends on where you are.

[I]n pre-relativistic mechanics, time is a special physical quantity, whose value is measured by physical clocks, that plays the role of the independent variable of physical evolution.

When two friends meet... after one has lived in the mountains and the other at sea level, the watches... will show different times. ...Neither is truer than the other. ...Times are legion: a different one for every point in space. ...there is a vast multitude of them. ...Every clock has its proper time. ...Einstein has shown how to calculate the difference... The world is not like a platoon advancing at the pace of a single commander. It is a network of events affecting each other. ...Physics does not describe how things evolve "in time" but how things evolve in their own times, and how "times" evolve relative to each other.
Time has lost... its unity.