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Albert Einstein (Germany 1879 – United States 1955) was a great physicist; though he was not a philosopher, his discoveries in the field of physics were so great that they had profound consequences in philosophy. He is considered by many people the greatest physicist, or even the most intelligent man ever existed. His equation E = mc² is very famous, meaning “Energy = mass (which has a meaning almost equal to “matter ”), multiplied by c², ie the speed of light squared”. Along with this equation, he developed his famous “theory of relativity”; some consequences of this theory help to get a general idea about it:
• matter can be transformed into energy, developing an enormous quantity of it, and vice versa; this means that, basing on physics research, we no longer know what the matter actually is, contrary to the clarity that came from Aristotle; we are used to thinking of energy as a characteristic possessed by objects: a table that is falling from a window has a certain amount of energy, which is easy to notice; according to Einstein’s theory, we can take part of the matter, suppose a table leg, and transform it into energy, for example transforming it into an increase in table speed; but, according to the same theory, it is also possible to do the opposite: take some energy and transform it into matter, as if to say: remove a bit of speed from the falling table and transform it into wood, to lengthen, for example, the table legs. All this may seem pure fantasy, but the construction of the atomic bomb is based precisely on this possibility of transforming part of the matter into pure energy. This phenomenon must not be confused with the energy that develops by burning the table or by exploding gunpowder: in the latter case, in fact, the quantity of matter (and therefore also of weight) always remains the same, although it is chemically transformed; even if the ashes added to the smoke produced by the burned table would give the impression that there has been a decrease in the quantity of matter, actually in that transformation the quantity of matter and the quantity of energy present in the world have always remained the same: if we could measure the weight of the world before and after the table was burned, we would notice that there would be no change; instead, after the explosion of an atomic bomb, there is a little less matter in the world, the whole world has become a little lighter, while the amount of energy present has increased in it.
• another consequence of the theory of relativity: time does not always flow with the same speed. As we move faster, it slows down, compared to those standing still, the closer we get to the speed of light; to illustrate this fact, the example of twin children has been devised: let’s suppose that one of two twins is placed in a spaceship, making a journey through space at the speed of light, that is 300,000 km per second. Let’s suppose that about 70 years pass on earth: the brother who has remained on earth has become oldnow; the spaceship returns and – surprise! – the child in the spaceship instead remained a child: that is, by traveling at the speed of light, time has stopped for him. There are still discussions about the precise reality of this phenomenon, but we are interested in the philosophical consequences of this physical phenomenon, that is the questions we are forced to ask ourselves: what is time? Is it an absolute thing, or is it conditioned by the set of matter and energy referred to? And what meaning do the words past, future, present have?
• finally, let’s consider even another consequence of the theory of relativity: the weight of an object also depends on the speed with which it moves: it increases proportionally, as its speed approaches that of light. The child on the star would not only see time stop, but would also see his weight become infinite.
After what has been said on the theory of relativity, we come to have a confirmation of what Nietzsche claimed: even the discoveries of physics force us to admit that, if we wanted to say what the world is and how it is made, with the clarity that Aristotle thought he had reached, we would no longer know what to say precisely, because we no longer understand what objects, energy, time, but also, therefore, man, life, existence are exactly.