Why is it anticipated that galaxies can collide if the universe is expanding?

In the 1920s, when Edwin Hubble observed that many galaxies were moving away from us, he pioneered the first discoveries that the universe was expanding. Andromeda is an exception to this situation. Because it moves towards the Milky Way Galaxy at 400,000 km per hour. However, it was not possible to say whether it was coming towards us until precise measurements were made using the Hubble Space Telescope or whether it would scrape us at an angle. According to the latest research, two galaxies may experience a massive collision 4 billion years later.

The events in the universe are shaped by the struggle between different forces. Dark energy is thought to be the reason for the acceleration of the expansion in the universe. Gravitational force is the force that holds the galaxies together. On a large scale, like galaxy clusters, galaxies are moving away from each other. However, in the denser parts of the universe, the effect of gravity begins to become apparent. Also, if the distance between the two galaxies is small enough, the galaxies are moving towards each other due to the mutual gravitational force between the galaxies. In a sense, we can say that the Andromeda Galaxy "fell" over the Milky Way.

However, the gravitational force created by the visible material is not enough to hold the galaxies together. Scientists think that galaxies and clusters of galaxies coexist, thanks to the dark matter that imparts gravity to the galaxies due to added mass.

In the early times when the universe was more intense than it is today, both the small and large-scale winner was the gravitational force, which allowed gas clouds to intensify to form stars and galaxies. If the amount of matter was more, the universe could collapse into itself. As the universe continued to expand, its density decreased due to its increasing volume, and the effect of dark energy became more pronounced. Expansion began to accelerate about 6 billion years after the Big Bang.