What is Dark Matter?

Dark matter is a type of matter that does not emit, absorb, or reflect light, making it invisible to telescopes and other instruments that detect electromagnetic radiation. It is thought to be composed of particles that interact weakly with regular matter and radiation, which is why it has eluded direct detection so far.

Evidence for Dark Matter

There are several pieces of evidence that support the existence of dark matter:

Galaxy Rotation Curves: Observations of the rotational speeds of galaxies show that the visible matter alone cannot explain the observed velocities. Dark matter is thought to provide the extra mass that keeps galaxies from flying apart.
Gravitational Lensing: The bending of light around massive objects, such as galaxy clusters, indicates the presence of unseen mass, which is attributed to dark matter.
Cosmic Microwave Background: Anisotropies in the cosmic microwave background radiation suggest the presence of dark matter and its influence on the early universe's large-scale structure.

Types of Dark Matter

While the exact nature of dark matter remains unknown, several theoretical candidates have been proposed, including:

Weakly Interacting Massive Particles (WIMPs): These hypothetical particles are among the leading candidates for dark matter and are predicted by certain theories beyond the Standard Model of particle physics.
Axions: These are hypothetical elementary particles that are extremely light and are considered a candidate for dark matter.
MACHOs (Massive Compact Halo Objects): These are astronomical bodies, such as black holes, neutron stars, or rogue planets, that could account for some of the dark matter mass.