Dark Matter

Dark matter is one of the big mysteries we all hear about. What makes it a mystery is how little we seem to know about it… but what do we know?

Dark matter is a hypothetical form of matter which appears not to interact with light—hence the name. So you might be wondering, if we can’t see it, how on earth do we know it exists? Well, we know it’s there because we observe certain gravitational effects which are seemingly unexplainable… unless there’s more matter involved than we can see. One of these is gravitational lensing, which we take a look at in another post. Others are the formation of galaxies and the structure of the universe, both of which can only be explained in the framework of general relativity if there was more matter present which we cannot actually see.

It is estimated that dark matter constitutes 85% of the total mass observed in the universe. (Crazy, I know)

What dark matter is exactly is the big mystery. The main theories are that it is either a yet unknown subatomic particle, or that it is composed of primordial black holes (black holes which formed soon after the Big Bang).