Dark Matter and the Mystery of Galaxy Motion

What is Dark Matter ?

One of the most intriguing mysteries of all time, dark matter. A hypothetical form of matter that is said to be 27% of all matter that is non-baryonic in nature ( all matter we come in contact with; matter made of protons, neutrons and electrons). Observable matter is around 5% and the rest is darkness ( the remaining 68% are darkness as a result of dark energy) . Scientists are u to come in direct contact with it but they have a pretty good evidence suggesting its existence, some of which is from the CMB ( read the blog post below ). Dark matter also keeps orbits and galaxies together, it acts like an invisible load of mass required to keep galaxies glued together. You're probably wondering why discovering we don't ever come in contact with is important, well knowing what makes up the universe will assist in the understanding of the universe as a whole. 

Matter quantities comparison between the beginning                                               Motion of galaxies (mostly clusters) with and without dark matter
​of the universe and the present.

History and Evidence of Dark Matter

Famous astronomer Fritz Zwicky discovered a weird phenomena that he named "missing mass". He realized that in the Coma Cluster (a cluster of galaxies) the stars accounted for only 1% of the mass required to hold the cluster together. This phenomena continued to be a mystery until Vera Rubin and W. Kent Ford proved their existence with the orbit speed of stars, and this so called matter could not reflect or emit light, hence the name dark matter. After its official existence, dark matter was observed through gravitational lensing as the dark matter bent space time and warped the passages of light, black holes have a similar effect.

Real image of gravitationally lensed images because of dark matter.

Representation of how gravitational lensing and space time warping works.

Final Thoughts and What is Know About Dark Matter for Now

We know dark matter is cold because of its slow movement, many prediction of different particles have been theorized because of this discovery, some of which are called WIMPS (weakly interacting massive particles). The rotation of galaxies and how they act are also affected and influenced by dark matter and that it also does not interact with the electromagnetic force but it does interact with gravity. Finally, we know we need to figure out what it is to get a full understanding of how our universe works and be able to accurately calculate galaxies' motion. Thank you and stay safe.