Does anyone understand quantum mechanics?
The theory that removed the foundations of physics at the beginning of the 20th century and that has turned out to be the most successful scientific theory in history, making possible the creation of almost all the inventions that make up today’s technology, from lasers to computers and other digital devices … That theory … We still don’t understand it!
The famous physicist Richar Feynmann said after receiving the Nobel Prize for his contributions to quantum mechanics: “If you think you understand quantum mechanics, you don’t understand quantum mechanics”. And, indeed, to this day there are several interpretations of quantum mechanics, which are incompatible with each other.
The point is, in order for the mathematics of quantum mechanics to operate, it is necessary that a mysterious phenomenon called “superposition of states” occur. In the classic mental experiment of Schrödinger’s cat, the kitty is physically alive and dead at the same time. It is not an optical illusion or that the animal is in an intermediate — semi-live or semi-dead state — but rather that the two states — alive and dead — are superimposed in the same wave function that is the physical and mathematical expression of the cat, as if a singer could sing simultaneously a do and a re.
This strange conundrum, to which quantum leads us, is at the root of all the questions it raises, and because of this, numerous interpretations have arisen that so far it has not been possible to verify or exclude.
The most common interpretation is the one called of Copenhagen, because it was introduced by quantum pioneer Niels Bohr, who was born in that city in 1885. According to this interpretation, quantum mechanics introduces a new category of existence that is different from the classical conception and that consists in a function of probabilistic wave, which in the case of Schrödinger’s cat combines both possibilities (alive and dead) in a single mathematical expression. Of course, at the moment the beholder enters into the scene, the function is said to “collapse”, and only in that moment the traditional form of existence arises, in which only one of the two possibilities is true.
The main critic of that interpretation was Albert Einstein himself, who coined his famous phrase “God does not play dice” (although he was probably an agnostic, but that is another story) to imply that the ultimate nature of things could not be probabilistic, and that if quantum mechanics did not allow us to investigate beyond that barrier, it was because it was “incomplete”.
One alternative interpretation to Copenhagen is that of parallel universes. Much of science fiction is based on this idea. Every time we make a decision or perform a random act, like throwing a coin, we are making the universe split into two or more possibilities. The “existence” would thus be conformed by an almost infinite set of universes where, as a whole, everything is literally possible. It has even been suggested that the so-called “Mandela effect” would have its origin in a kind of communication between these parallel universes.
According to this approach, for Schrödinger’s cat, at the moment when the subatomic particle makes the fatal decision that will or will not preserve the cat’s life, it makes the universe become two: one where the cat will survive and another where it will die. The whole universe doubles, including the cat and the observer, so we now have two identical copies of it (identical except for the cat). None of the two copies of the observer knows if the cat is alive or dead, until the moment of observing it. Under this conception, there is nothing that “collapses” here; however the existence of the observer, his time-line, his life and his consciousness, takes one of the two alternatives. By the way, in a parallel universe, the other copy still exists and it is as valid and legitimate as the one we call the first.
A clear difference between the two interpretations is that in an existence composed of parallel universes, each being lives the longest possible life, in the sense that at every moment of our life we are living in at least one universe in which we are still alive, and all the universes in which we no longer exist have also ceased to exist, at least for us.
The detractors of multiple universes habitually argue that it is unnecessarily overflowing and copious. The infinite proliferation of universes is something nonsensically onerous. It does not seem reasonable that for every bifurcation of possibilities, at the level of individual subatomic particles, a bipartition of the entire universe should be made! According to this interpretation God does not play dice but poker, and it does so by hiding a card factory up his sleeve; something that simply seems absurd for many of us.
There are other interpretations of quantum mechanics, but the two I have presented here are the most common. As you can see, both do not differ so much in their physical aspects but in the philosophical view. And that is why nobody really understands quantum mechanics. Nobody really knows what it means in a very deep level. At least until now.
