I am very often asked questions whose cause is a poor understanding of the theory of relativity. For example:
If photons have no mass, then why does the gravity of black holes act on rays of light?
In this article I will talk about the theory of relativity in as simple a language as possible without complicated formulas and excessive nonsense. So let’s begin.
Einstein’s elevator
It all started with Einstein. He was sitting there in Switzerland, working as a clerk in the patent office. He had plenty of free time (how many patents there are in Switzerland) and he used this time to think about the nature of light and came up with the following mental experiment:
Suppose a man is inside a locked elevator standing on the ground. If he tosses, for example, an apple, it will fall with an acceleration equal to g. And what if somewhere in space there is another exactly the same elevator cabin, but it moves with acceleration equal to g? Is there any way to experimentally figure out which of the two elevator cabins we are in? As it turned out — there is no way to distinguish the first situation from the second. All physical processes will run exactly the same inside both cabins. From this Einstein concluded that there is no difference between gravity and acceleration.
