Scientists have long proved that the universe is gradually expanding. And how many more such galaxies in outer space! It is worth understanding what expansion of the Universe is and how a collision of galaxies occurs.

What does the expansion of the universe mean?

This is a complex phenomenon, the essence of which is the expansion of outer space. It is hard to imagine how scientists living on Earth, such a small object against the backdrop of the universe, managed to learn about this extension. This was first discussed in 1886, when it became apparent that space objects were moving.

In the future, many scientists tried to create various theories regarding this phenomenon. They also attempted to calculate the distance to other galaxies. The study of this issue was given with varying success. We managed to find out more useful information thanks to the work of the scientist E. Hubble. In 1929, he managed to formulate and experimentally confirm the law that describes the expansion of the universe. Using a telescope of 2.54 m, he was able to view the nearest galaxies on a significantly enlarged scale. Understanding which stars enter there provided an opportunity to measure the distance to them.

Thus, it was possible to find out that the farther away a galaxy from our planet, the faster it moves in the opposite direction. This discovery is based on a cosmological redshift.The farther the object, the lower the radiation frequency it has.

To understand the essence of the expansion of the Universe, it was easier to draw a simple analogy and compare it with a balloon. For example, on a slightly inflated ball, you can draw points in different parts of its surface. If you take and inflate the same ball even more, it will increase in size and the distance between all points will increase. At the same time, the points will not change their location, since only the surface of the balloon on which they are painted changes. And if you look at the situation from a certain point, then all the others move away from it.

The principle of expansion of the Universe works in approximately the same way. Each galaxy is a point, and the Universe itself is the surface of a balloon. Thus, the galaxies remain in place, and only the outer space in which they are contained moves. The galaxies themselves are gradually moving away from each other.

Why do galaxies collide?

In this case, a logical question arises: how can galaxies collide if, according to the principles of the expansion of the Universe, the distance between them is constantly increasing? The fact is that galaxies do not exist separately in space. The universe is a kind of hierarchy. Nearby galaxies turn into clusters, and those, in turn, form superclusters of galaxies.

The expansion of the universe occurs everywhere equally, uniformly and it acts on a large scale. Within the same cluster of galaxies are interconnected by gravitational attraction.In addition, they are relatively close to each other - at a distance of about a couple of hundred thousand light-years. Therefore, such objects can approach or move away, regardless of the universal expansion of the universe. Because of this, collisions of galaxies occur.

Interesting fact: Earth is in the Milky Way galaxy. She, in turn, is part of the Local Group, where in addition to small galaxies there are large ones - Triangle and Andromeda. It is estimated that after 4 billion years, a collision between our Galaxy and Andromeda could occur. And 1 billion years earlier, you can see the stars and other objects of Andromeda just by looking at the sky.

When it comes to superclusters of galaxies, there is no relationship between them - there is no gravitational attraction. In other words, one cluster of galaxies is moving away from another.

Galaxies form clusters and superclusters. Within the same cluster, they are relatively close to each other and have gravitational attraction. In superclusters, galaxies are in no way connected. The expansion of the universe is the expansion of outer space, in which galaxies remain motionless, but the distance between them grows. The collision of galaxies occurs within the same cluster, because they are attracted to each other faster than the universe expands.