How do Galaxies Collide in an Expanding Universe?

The Big Bang theory proposes that the universe originated from a singular point and rapidly expanded, distributing matter and energy throughout the cosmos.

This expansion resulted in the movement of all celestial bodies away from each other.

Despite this continuous expansion, galaxies are observed colliding with each other, posing the question of how these collisions take place in an ever-expanding universe.

Gravitational Attraction Between Galaxies

One crucial factor contributing to galaxies colliding in an expanding universe is the gravitational attraction between them.

While the universe itself is expanding, the force of gravity can counteract this expansion, causing galaxies to be drawn towards each other.

If the gravitational pull between two galaxies is strong enough, it can override the effects of expansion and lead to a collision.

Case Study: Andromeda and Milky Way Galaxies

An example of this phenomenon is the impending collision of the Andromeda and Milky Way galaxies, currently on a collision course.

Despite the universe's expansion, the gravitational pull between these galaxies is significant enough to overcome the expanding space between them, ultimately leading to their collision in the distant future.

Impact of Dark Matter

Additionally, dark matter, an invisible and elusive form of matter that makes up a large portion of the universe's mass, also plays a crucial role in the dynamics of galaxies.

The gravitational influence of dark matter can significantly affect the motion of galaxies, contributing to their collisions despite the ongoing expansion of the universe.

Cosmic Microwave Background Radiation as a Reference

While the universe's expansion makes it challenging to define a distinct center, the cosmic microwave background radiation (CMBR) serves as a crucial reference point.

It provides insights into the structure and movement of the universe, aiding in our understanding of the dynamics of galaxies and their collisions.

A Thought-provoking Perspective

Considering the collision of galaxies in an expanding universe offers a riveting perspective on the intricate dynamics at play in the cosmos, challenging our understanding of the universe's evolution and structure.