superposition
state · uncertainty · collapse
A quantum object doesn't have to be in just one state — it can exist in a mix of multiple states at the same time. Physicists have pushed this from single particles to molecules of 2,000 atoms, and even further: a neutrino created as one "flavor" oscillates between flavors as it travels, sometimes over distances of 150 million kilometers, proof that superposition survives far past ordinary intuition. But the instant any of this is measured, it collapses down to a single, definite outcome. Why measuring something forces that choice — and how it actually happens — is still one of the biggest open questions in physics.