Chapter 30, Problem 96A

To determine

To Explain:

The understanding of dark matter in the universe and reason that cosmologists think it must exist and of what it is made of.

Answer to Problem 96A

The universe is made up of around $85\%$ of dark matter and it is required to explain the rotation of galaxies in the universe. It also gives the explanation about the expansion of universe. Dark matter is not an ordinary matter but it interconnects with the ordinary matter with the help of weak nuclear forces.

Explanation of Solution

Introduction:

Dark matter is basically a type of matter that is believed to be contributing to a large amount of the mass which is present in the universe. Dark matter cannot be observed directly with the help of telescopes. It does not emit energy neither it interacts with light or any other radiations.

The dark matter is composed of particles which known as baryons. Dark matter is very important as it affects gravity and many components that exist in the universe but are unknown to us. It is believed that dark matter is non interacting in nature and gravity is the only way to detect the presence of this kind of matter. It is important to study dark matter in order to understand the rotation of galaxies and the formation of clusters of galaxies.

Conclusion:

The universe is composed of around $85\%$ of dark matter and it is required to explain the formation of galaxies and other such structures in the universe.