20 Big Mysteries We Still Haven’t Solved in Space

For years, astronomers counted the visible stars, dust clouds, and galaxies in space, yet the figures still did not add up. About half of the normal matter expected to exist in the universe appeared to be absent from those counts. Researchers recently detected much of this missing material as hot, thin gas spread between distant galaxies. Astronomers welcomed the resolution of this longstanding puzzle because it confirmed that their math had been right all along.