Seven Brief Lessons on Physics

The German physicist Max Planck calculated the electric field in equilibrium in a hot box. To do this he used a trick: he imagined that the energy of the field is distributed in “quanta,” that is, in packets or lumps of energy. The procedure led to a result that perfectly reproduced what was measured (and therefore must be in some fashion correct)

do you remember the periodic table of elements, devised by Dmitri Mendeleev, which lists all the possible elementary substances of which the universe is made, from hydrogen to uranium, and which was hung on so many classroom walls? Why are precisely these elements listed there, and why does the periodic table have this particular structure, with th

It was Bohr who understood that the energy of electrons in atoms can take on only certain values, like the energy of light, and crucially that electrons can only “jump” between one atomic orbit and another with determined energies, emitting or absorbing a photon when they jump. These are the famous “quantum leaps.”

This hypothetical final stage in the life of a star, where the quantum fluctuations of space-time balance the weight of matter, is what is known as a “Planck star.” If the sun were to stop burning and to form a black hole, it would measure about one and a half kilometers in diameter. Inside this black hole the sun’s matter would continue to collaps

Another of the consequences of the theory, and one of the most spectacular, concerns the origins of the universe. We know how to reconstruct the history of our world back to an initial period when it was tiny in size. But what about before that? Well, the equations of loop theory allow us to go even further back in the reconstruction of that histor

Heisenberg imagined that electrons do not always exist. They only exist when someone or something watches them, or better, when they are interacting with something else. They materialize in a place, with a calculable probability, when colliding with something else. The “quantum leaps” from one orbit to another are the only means they have of being

Quantum mechanics and experiments with particles have taught us that the world is a continuous, restless swarming of things, a continuous coming to light and disappearance of ephemeral entities. A set of vibrations, as in the switched-on hippie world of the 1960s. A world of happenings, not of things.

Another way of posing the problem is to ask oneself: what is the “present”? We say that only the things of the present exist: the past no longer exists and the future doesn’t exist yet. But in physics there is nothing that corresponds to the notion of the “now.” Compare “now” with “here.” “Here” designates the place where a speaker is: for two diff

Heisenberg imagined that electrons do not always exist. They only exist when someone or something watches them, or better, when they are interacting with something else. They materialize in a place, with a calculable probability, when colliding with something else. The “quantum leaps” from one orbit to another are the only means they have of being