Is there any experimental difference in gravitational force for a non-observed particle versus an observed particle in a gravitational field? Basically my question is if they fall with the same acceleration? The observed particle is observed the entire fall, but both the observed and the non-observed particles are detected at some given distance further down at bottom. (Probably an average of all tests in the non-observed particle case is needed in order to compare it to the observed one) The situation might be similar for electromagnetic waves. Is there any quantum gravity theory that suggests that they should not fall with the same acceleration?