The universe is full of mysteries, but one of the biggest is called ‘dark matter’.
This is what we know so far.
When we look at the Milky Way or any other galaxy in the universe, we can see that they’re made up of things like stars, planets, nebulae, and black holes. They all have mass and when we add them up, we should end up calculating the mass of the galaxy.
But when we put this calculated mass into a computer simulation of a galaxy, the galaxy flies apart instead of rotating – which is what we observe through our telescopes.
After checking the simulation many times, physicists have determined that the mass we calculated must be incorrect. It is not enough to hold a galaxy together.
The leading solution we have to this problem is that, spread throughout the Milky Way and other galaxies, there must be a ghostly substance that creates the rest of the missing mass.
It must be ghostly because we have not been able to see or detect it in any way yet. This is why it’s called ‘dark matter’.
When we adjust our simulations to include dark matter, the math works and the galaxy sticks together.
But for the simulations to work, each galaxy has to have way more dark matter than ordinary matter – by almost 8 to 1.
Other than these fairly basic predictions, we don’t know a thing about dark matter. But because there’s so much of it, that means that we don’t understand the substance that makes up 85% of all matter in the universe.
Just like with dark energy, the exact nature of dark matter remains one of the major mysteries in modern physics.