Gravity vs. Superposition: Why the World Isn't Blurred ✎ express
In the quantum world, an object can be in several places at once. Yet in everyday life we see things strictly in their places. The reason is gravity. A massive star under its own weight inevitably collapses into a black hole or a neutron star, but it can't be both at the same time. Similarly, a heavy body in quantum superposition loses its fuzziness: its own gravity makes a dual state impossible.
An equation combining the ideas of Schrödinger and Newton showed that spacetime curvature conflicts with superposition. The probability wave collapses, and the collapse time is inversely proportional to mass — heavy systems acquire definiteness almost instantly.
A surprising twist: superposition generates two conflicting versions of spacetime geometry, and this incompatibility triggers an immediate choice. Even in the falling elevator of Einstein's thought experiment, weightlessness doesn't help — the accumulated mismatch inevitably leads to the same outcome. Thus gravity turns the fuzzy quantum world into a stable reality.
If the Moon could exist in quantum superposition, its own gravity would collapse the uncertainty in billionths of a second.