>>16711813 (OP)it's not that gravity breaks down. yes, according to the naive model of gravity, the neutrino and the hammer fall at the same rate. the problem here is this assumes no other interactions (for example, with the feather and the hammer, we assumed no air drag). in other words, this conclusion works when gravity is the only force the objects experience. the neutrinos will interact with quantum fields, whereas the hammer does not. these quantum fields will destroy the neutrino before it ever completes the fall