There is almost nothing we know about dark matter. We can’t even be sure that it’s really there, but we’re fairly sure something is there. It’s the only way our calculations about the universe make sense.
First off, what is dark matter? Well, that’s one of the many things we don’t know about it. We know that it does not reflect light particles (light passes through it) so we can’t see it, hence “dark” matter. However, it does interact with gravity, and using that we can “see” it in a sense. The path of light passing around high concentrations of dark energy is bent, so the image of stars behind the dark matter is warped, and thus we know something stands between us and the star.
Without dark matter, much of our universe wouldn’t make sense. After observing countless galaxies, scientists found that there simply isn’t enough normal matter within the galaxies for gravity to hold it together; the stars in the galaxies should just fly apart. Thus, there must be something else there, something that we cannot see, that is holding together the galaxy. Scientists believe this is dark matter. By their calculations, there is approximately 5 times more dark matter in the universe than there is normal matter, meaning that everything we can see including (stars, galaxies, black holes, and ourselves) is merely a small fraction of what exists in our universe. In a sense, we are the “weird” normal matter.
In the end, we really only know three things about dark matter:
- There is something there.
- It only interacts with gravity, and not with light.
- There is A LOT of it.
Aside from that, we’re in the dark.