The Case of the Missing Dark Matter
Physicists don\u2019t know much about dark matter. They can\u2019t agree on what it\u2019s made of, how much a single particle weighs, or the best way to construct a Play-Doh diorama of it. (How would you do it? Dark matter is invisible\u2014light doesn\u2019t interact with it at all.) Nobody has ever caught a dark matter particle on Earth. But after 30-plus years of telescope observations, most researchers do agree on one thing: The universe contains a lot of it.