What Is Dark Matter?

First and perhaps most perplexingly, researchers remain unsure about what exactly dark matter is. Originally, some scientists conjectured that the missing mass in the universe was made up of small faint stars and black holes, though detailed observations have not turned up nearly enough such objects to account for dark matter's influence.

Astrophysicist Paul Sutter explains what #darkmatter is and how physicists can determine the invisible substance exists.