The ability to live in coherent superpositions is a signature trait of quantum systems. ~ Brazilian physicist Isabela Silva
Quantum superposition assumes that the uncertainty principle is real. At every moment, any physical quantum, such as an electron, exists in all possible states simultaneously until it manifests, whereupon its result is only 1 configuration.
While single particle superpositions can be fairly stable, macroscopic objects never are. The formation of macroscopic superpositions, in which numerous quantum components must maintain a precise relationship with each other, are disrupted by continual environmental influences.
Gravity as an environment induces the rapid decoherence of stationary matter superposition states when the energy differences in the superposition exceed the Planck energy scale. ~ English physicist Miles Blencowe
A disruption of superposition decoheres a system into a specific state. Gravity is a spacetime disturbance that pushes the quantum components of a system out of sync as they travel across a superposition.
Quantum particles are largely beyond the reach of gravity. An atom is touched by it. A molecule feels gravity, however slightly.
Decoherence rate rises by the square of the energy difference between 2 states in a superposition. The more there is to a physical system, such as a proton versus an electron, the greater the energy differences in superposition states.
Gravitational waves are pervasive and inescapable. They are part of the cosmic background, an echo of inception, and a cousin to the electromagnetic radiation which also pervades. Superposition loses its grip on the macroscopic world via gravity, giving rise to the predictable realm described by classical physics.
Various experiments have lent credence to quantum superposition.