More than 90 percent of all the stuff in the universe is made up of a mysterious substance called dark matter. Dark matter holds together galaxies like glue, but we don’t know what it is.
Priyamvada Natarajan is a Yale astrophysicist who’s part of a team that’s produced the highest-quality image of dark matter yet. She’s also the author of a new book, “Mapping the Heavens,” about the history of our investigations into cosmic phenomena.
“There are basically about a thousand galaxies that appear to be held by the gravity of dark matter,” she says. “This is how the presence of dark matter was inferred in the first place in 1937. Galaxies are moving around faster than they would if they were only affected by the stuff you can see. In order to explain the motions of these galaxies, you need a huge unseen component.”
Scientists back in 1937 kind of rolled their eyes at the existence of dark matter. But a lot has happened in the last century. We’ve learned the universe is expanding, and we’ve learned that gravity bends time as well as space. Scientists discovered black holes -- which are collapsed stars so heavy even light can’t escape them. In the past hundred years, Natarajan says our whole notion of the universe has changed.
“Until the 1900s, we thought we were the only galaxy, that’s all there was,” she says. “Then the astronomer Edwin Hubble realized that there were external galaxies. And now we know there are billions and billions of galaxies.”
That knowledge can lead to some soul searching for humanity.
“We know our place, that we are significant and insignificant simultaneously,” she says. “We’re significant because we’ve figured this out and we’re here. We’re insignificant because we have now discovered there are thousands of planets around other stars and who knows what kind of life might be lurking there, might be possible?”
Natarajan says our own age is often referred to as the golden age of cosmology.
“So we have this grand convergence of ideas, instruments, technologies and our capabilities,” she says. “That’s why we’re seeing these very rich results. We really are on a fast forward at a much higher speed than ever before. So it’s very exciting to be alive now and witnessing all of this.”
Natarajan hopes her work on dark matter might lead to some new discoveries soon. She thinks the map her team has made could lead scientists to figure out what dark matter is. So before too long, we might be able to put a name to the nameless stuff that makes up most of our universe.
