Question

What is dark matter?

Answer 1

Dark matter is a hypothetical form of matter thought to account for approximately 85% of the matter in the universe. Dark matter is called "dark" because it does not appear to interact with the electromagnetic field, which means it does not absorb, reflect, or emit electromagnetic radiation and is, therefore, difficult to detect.

Answer 2

Dark matter was first suspected in clusters of galaxies when the galaxies were found to move with too high a speed to be retained in the cluster by their gravitational influence on each other