The relationship between dark matter and velocity is primarily observed in the context of galactic dynamics. Dark matter is an invisible and mysterious form of matter that does not emit, absorb, or interact significantly with electromagnetic radiation, making it difficult to detect directly. However, its presence can be inferred through its gravitational effects on visible matter and the motion of celestial objects.
In galaxies, the visible matter, such as stars and gas, is not sufficient to explain the observed velocities and dynamics of stars within the galaxy. The visible matter alone would not generate enough gravitational force to hold the galaxy together. The observed velocities of stars in galaxies indicate that there must be additional mass present, which we refer to as dark matter.
The relationship between dark matter and velocity arises from the gravitational effects of dark matter on visible matter within galaxies. Dark matter, which is thought to be distributed in extended halos around galaxies, exerts gravitational pull on stars and gas, affecting their velocities.
In galactic systems, the velocities of stars and gas depend on the combined gravitational influence of visible matter (such as stars, gas, and dust) and dark matter. The presence of dark matter significantly enhances the gravitational force, which in turn affects the velocities of stars and gas in a galaxy.
Observations indicate that the velocities of stars and gas in galaxies remain high even in regions where the visible matter density decreases significantly. This implies the presence of unseen mass, i.e., dark matter, contributing to the gravitational pull and maintaining high velocities at larger distances from the galactic center.
In summary, the relationship between dark matter and velocity is that dark matter's gravitational effects influence the observed velocities of stars and gas within galaxies, contributing to the overall dynamics and structure of galactic systems.