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A new thought experiment indicates that quantum mechanics doesn’t work without strange numbers that turn negative when squared.

Twenty years ago, physicists set out to investigate a mysterious asymmetry in the proton’s interior. Their results, published today, show how antimatter helps stabilize every atom’s core.

The result highlights a fundamental tension: Either the rules of quantum mechanics don’t always apply, or at least one basic assumption about reality must be wrong.

It has been thought of as many things: a pointlike object, an excitation of a field, a speck of pure math that has cut into reality. But never has physicists’ conception of a particle changed more than it is changing now.

In a landmark series of calculations, physicists have proved that black holes can shed information.

We’ve created a new way to explore the fundamental constituents of the universe.

Recent experiments show that particles should be able to go faster than light when they quantum mechanically “tunnel” through walls.

Physicists have identified an algebraic structure underlying the messy mathematics of particle collisions. Some hope it will lead to a more elegant theory of the natural world.

We asked four physicists why gravity stands out among the forces of nature. We got four different answers.