Seven Brief Lessons on Physics
Carlo RovelliQuotes
Why does heat go from hot things to cold things, and not vice versa?
It is a crucial question, because it relates to the nature of time. 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. For example, for the motion of the planets of the solar system
Our universe may have been born from a bounce in a prior phase, passing
through an intermediate phase in which there was neither space nor time.
"Genius hesitates". Diğerleri de işte bildiğiniz gibi.
These simple and clear lines are the real birth certificate of quantum theory. Note the wonderful initial ‘It seems to me …’, which recalls the ‘I think …’ with
which Darwin introduces in his notebooks the great idea that species evolve, or the ‘hesitation’ spoken of by Faraday when introducing for the first time the
revolutionary idea of magnetic fields. Genius hesitates.
Einstein, Bern, 17 Mart 1905
It seems to me that the observations associated with blackbody radiation, fluorescence, the production of cathode rays by ultraviolet light, and other related phenomena connected with the emission or transformation of light are more readily understood if one assumes that the energy of light is discontinuously distributed in space. In accordance with the assumption to be considered here, the energy of a light ray spreading out from a point source is not continuously distributed over an increasing space but consists of a finite number of ‘energy quanta’ which are localized at points in space, which move without dividing, and which can only be produced and absorbed as complete units.
He aimed at understanding how this ‘gravitational field’ worked, and how it could be described with equations.
And it is at this point that an extraordinary idea occurred to him, a stroke of
pure genius: the gravitational field is not diffused through space; the gravitational field is that space itself. This is the idea of the theory of general
relativity. Newton’s ‘space’, through which things move, and the ‘gravitational
field’ are one and the same thing.