Dark Matter

Dark matter is matter that cannot be directly seen because it does not interact with light. This mysterious matter makes up the majority of mass in a galaxy. Although we cannot see dark matter we know that it is out there because we can see it effecting the motion of the stars in a galaxy and gravitational lensing. The first piece of evidence for dark matter is in the way we have observed galaxies moving. You would likely expect their behavior to replicate that of the Sun and the planets, with the velocity of planets being faster the closer they are to the Sun, and slower as we move out from the center of mass. This is due to gravity, the larger a mass is the more gravitational pull it has, and this attracts other near objects. The closer you are …show more content…
To understand how gravitational lensing proves the existence of dark matter you first need to know this, mass bends light. This means that the mass of an object, in this case dark matter, will actually bend space and alter the path of surrounding object, which in this case is light, resulting in what is called the bending of light. This distortion of space deflects the path of light elsewhere. Gravitational lensing can be observed when a far galaxy’s light is seen passing through a near-galaxy, if these galaxies line up we will not see the farther galaxy, but can observe its light around all sides of the nearer galaxy – in the shape that is referred to as an Einstein ring. Gravitational lensing gives us great insight into dark matter and allows us to measure how much dark matter is in a galaxy and see how it is distributed throughout that galaxy. Without dark matter there is not enough mass to result in the amount of gravitational lensing we observe in the universe, there simply is not enough mass in the visible universe to do so. This means that there must be other mass out there, that we cannot see, that is causing this lensing