Scientists finally managed to understand why galaxies collide when the universe expands. As the researchers, who have spent a lot of time on this question, explained, the space stretches between all the objects in the Universe. At the same time, people cannot notice this, and for good reason.
As the Hubble law states, the speed at which bodies are removed from each other directly depends on the distance between them. As an example, experts suggest imagining a balloon that has four points. When this ball is inflated, the distance between these points changes.
And some points are removed at much greater distances than others. This discrepancy is very easy to explain. The fact is that the space is stretched equally everywhere. Therefore, if at first the amplitude between them was large, then the effect of their removal from the ball would be simply huge.
The process of expansion of the Universe works in exactly the same way. For example, from our planet to the moon is more than 384 thousand kilometers. According to the same Hubble law, in order for a satellite to go one kilometer from Earth, you need to wait about 12 thousand years. If you look at it against the background of infinity, then almost any time may seem insignificant.
But do not forget about another factor, which is called gravity. All the bodies that are in the solar system are interconnected. If the Earth satellite is one kilometer away from us, it will be returned by gravity.
According to scientists, at enormous distances, the force of gravity is simply indescribable, so it can easily hold any of the cosmic bodies in one place. It is for this reason that galactic collisions occur. The gravitational attraction of galaxies acts much faster than stretching the space.