The Hunt for Dark Matter: Where We Stand in 2023

The Enigma of Dark Matter

Dark matter is one of the most fundamental mysteries of the universe. It makes up about 85% of the matter in the universe, but we have no idea what it is made of or how it works. It is invisible to light and does not interact with ordinary matter in any way except through gravity.

The existence of dark matter is inferred from its gravitational effects on visible matter. For example, galaxies spin too fast to be held together by the gravity of the stars and gas we can see. This suggests that there is a lot of invisible mass, or dark matter, surrounding them.

Another line of evidence for dark matter comes from gravitational lensing. Gravitational lensing is when the gravity of a massive object bends light from a distant object. This can cause the distant object to appear distorted or magnified. Scientists have observed gravitational lensing by clusters of galaxies, which suggests that these clusters contain a lot of dark matter.

Despite the strong evidence for its existence, we still do not know what dark matter is made of. There are many different candidates, including weakly interacting massive particles (WIMPs), axions, and sterile neutrinos.