Question: what is dark matter

Andres Olivares del Campo answered on 5 Nov 2016:

In the universe we have normal matter, like neutrons, protons and electrons which make up atoms like Hydrogen, which make up molecules like water, which ultimately, make up our own bodies!
Now, dark matter is just like this type of matter we see around us but with a small difference, it does not interact with light or other subatomic forces. All this means is that, we can’t see it! The reason why we see water, for example, is because the water molecules are constantly absorbing and emitting light (photons) which we see. Dark matter does not do this and therefore we cannot directly observe it. However, we know it weights, because we can look at our skies with huge telescopes, and see some galaxies rotate faster than they should! Therefore, something heavy must be there even if we cannot see it and that is what we called dark matter.