The Universe Would Be Very Different Without Dark Matter
“Finally, the smallest galaxies of all — the ones that contain only hundreds or thousands of stars — wouldn’t be able to exist at all. In our Universe, they arose from a clump of normal-and-dark matter of approximately 100,000 solar masses, where an episode of star formation ejected the gas. Still, the dark matter persisted, and holds the stars together in their own bound structure even to the present day. In a Universe without dark matter, that same episode of star formation would blast the proto-galaxy apart entirely, leaving only a slew of individual, unbound stars behind.
There are many different lines of evidence that point towards dark matter’s existence, but it’s perhaps a little more interesting to consider all the ways our Universe would be different — and inconsistent with what we observe — if it had no dark matter at all. If you enjoy the fact that the Universe is held together as well as it is, you have dark matter to thank for it. Even if you don’t believe in it, it’s a key ingredient in the Universe that led to you.”
Happy Valentine’s Day, dark matter! I know you don’t get nearly enough love on even a normal day of the year, so on this special day, don’t forget to carve out a piece of your heart for the unseen-but-important “glue” that holds the Universe together.