Physicists are reimagining dark matter

Readers ofthis paper will probably need no reminder that most of the universe is missing. The atoms and light you see—from people to planets, stars and galaxies—make up just 5% of the universe. The rest is a two-part mystery—a substance called “dark energy”, which pushes space apart, comprises 68% of the cosmos; what’s left, around 27%, is dark matter.Dark matter emits no light and scientists only know it exists because, when they look into the night sky, they see galaxies rotating a lot faster than they should. The laws of physics suggest that these galaxies should tear themselves to shreds at such colossal speeds. But astronomers do not see galaxies flying apart, which implies that there is a lot more stuff in them than can be observed in the form of stars, and therefore more gravitational force holding everything together.