Science has long been puzzled by the matter in our universe. We know galaxies are composed of stars, dust, and.. something else. Why? Well, because it’s theoretically impossible for a galaxy made up of only what we’ve seen so far to exist – it would be torn apart because gravity would not be strong enough. Even the estimated 100 billion stars in the Milky Way can’t possibly generate enough energy to hold the galaxy together at its mind-blowing speed of 828,000 kilometers per hour. The Milky Way’s arms are essentially spinning through space, bringing the sun and entire solar system with them.
Enter dark matter, the explanation scientists have come up with to explain why galaxies haven’t ripped apart. They think it’s what’s giving galaxies extra mass to generate enough gravity to hold together. But they haven’t been able to find out much about it; in fact, no direct evidence of dark matter has even been found. Part of that is because it doesn’t interact with the electromagnetic force, which is a fancy way of saying that it doesn’t reflect, emit, or absorb light. And what’s more, dark matter is estimated to make up 27% of the total mass in the universe, while the matter we know about that makes up stars and galaxies is only about 5% of the total universe. Crazy, right?
So we know what dark matter is, but what’s it actually made of? Scientists have proposed that it may be made of something called WIMPs, or Weakly Interactive Massive Particles. These are a theoretical type of subatomic particle that hasn’t actually been discovered yet, but scientists know what their specifications would have to be: a mass between one and 1,000 times that of a regular proton, so they’re massive enough to clump together, and “weakly interacting,” meaning they hardly interact at all with regular matter.
Many experience with so-called “WIMP Detectors” have tried to find WIMPs here on Earth deep underground. One of the most prominent is the LUX experiment, made possible by a collaboration of more than 100 scientists. Buried more than a mile underground in the hills of South Dakota is an enormous tank of liquid xenon. The xenon is supposed to light up, producing a small electrical charge, whenever any of its atoms come into contact with WIMPs, or dark matter. While no WIMPs have been detected yet, scientists are working to develop an even more sensitive apparatus that may crack the mystery of dark matter wide open.