How is the rotation curve of galaxies connected to dark matter?

The rotation curve of galaxies is connected to dark matter through its gravitational effects.

Galaxies rotate around their centres, and the speed of rotation is expected to decrease as you move further away from the centre. However, observations have shown that the rotation curves of galaxies remain flat, indicating that there must be more mass present than what we can see. This is where dark matter comes in.

Dark matter is a hypothetical form of matter that does not interact with light or other forms of electromagnetic radiation, making it invisible to telescopes. However, it does have mass and therefore exerts a gravitational force on surrounding objects. The presence of dark matter can explain the observed flat rotation curves of galaxies, as the additional mass from dark matter provides the necessary gravitational force to keep the outer parts of the galaxy rotating at the same speed as the inner parts.

The exact nature of dark matter is still unknown, and scientists are actively researching and developing theories to explain its properties. However, the evidence for its existence is strong, and its gravitational effects on the rotation curves of galaxies provide some of the most compelling evidence for its presence.