A person under two lamps casts two shadows: close lamps give merged shadows, distant lamps make them diverge. Similarly, a massive object in quantum superposition, being in two places at once, curves space twice. Einstein showed that mass curves space — like casting a shadow. In superposition, two overlapping gravitational shadows emerge.
Scientists calculated how similar these two gravitational 'shadows' are, and called it the contrast. For small mass, the shadows are almost identical — the contrast is high. As mass or distance increases, the contrast drops, triggering a cascade of quantum effects: entanglement (we learn the particle's position from the field), entropy (a measure of uncertainty), decoherence, and wave function collapse — gravity seemingly forces the object into one location. An experiment with gravity as a quantum field (obeying the laws of the micro-world) is ready to test this.
A vibrating object would additionally create gravitational waves — ripples in space, further confirming the quantum nature of gravity.
🎯 Schrödinger's famous cat, originally a joke, now aids scientists: instead of cats, they smear nanodiamonds through space to test quantum gravity.