The equivalence principle applies to the quantum realm.

Scientists conducted experiments using rubidium atom clouds cooled to near absolute zero and Galileo quantum interferometers to test the principle of equivalence in the quantum realm. The results showed that this principle applies in the quantum domain and is consistent with predictions of gravitational effects on quantum waves. This research, published in *Science Advances*, aims to resolve the issue of the unsuccessful integration of Einstein’s general theory of relativity and quantum mechanics. Experiments demonstrated that for observers observing free fall, the phenomenon of gravitational disappearance locally also holds true at the quantum scale. Although this study does not unify the aforementioned theories, it takes a step toward achieving this goal.