Dark matter is essentially the glue holding the universe together, according to Nicole Gugliucci, physics professor at St. Anselm College.
What is dark matter?
"Dark matter is this name that we give for something that has been detected, but we don't know what it is."
But there must be something else out there.
“There's not enough of that in the galaxy, for example, to explain the galaxy's rotation,” Gugliucci said. And whatever particles make up dark matter don’t interact with light.
According to NASA, dark matter makes up about 27% of the universe.
How do we know it even exists?
According to NASA, when scientists observed two galaxy clusters — collections of galaxies that are bound together by gravity — colliding, they were able to measure particles of normal matter and clusters of something else.
However, Gugliucci said some scientists have a different theory.
“There [have] been some hypotheses that instead of it being matter that we can't see,” Gugliucci said, “that the laws of gravity as we know it aren't quite correct.”
If that were true, it wouldn’t be the first time scientists have had to update their understanding of the universe.
“The classical gravity of Isaac Newton was surpassed by Einstein's general relativity,” Gugliucci said. “And so some folks have theorized that there could be a change to that — they call that modified gravity — but the observations of dark matter don't quite line up with that.”
Gugliucci is talking about those galaxy clusters coming into contact with each other.
“When they merge and pass through each other, the dark matter doesn't end up where it should, if it's modified gravity,” she said. “It ends up where it should if it's some type of particle.”
Find more information about the latest studies of dark matter on NASA’s website.
If you have questions about the night sky, send us an email, cosmic@ NHPR.org.
