Question: what is dark matter

Chris Werner answered on 11 Nov 2017:

Glad you asked this again here as its a very interesting topic! Dark matter is incredibly strange as scientists who study it think it makes up about 80% of all matter in the universe, the remaining 20%, known as baryonic matter (fancy way of saying protons, neutrons, electrons, everything we can see and touch). Dark matter itself is invisible, it emits no light, no energy. So what’s the point of it and why does it even exist, and how can we know its there you may ask! We know its there due to the movement of the stars, and because in our current understanding of the laws of physics, it needs to be there to hold the universe together. Theres a great example of a galaxy I’ve found in an article (https://www.space.com/33850-weird-galaxy-is-mostly-dark-matter.html) made up of 99.9% dark matter.