In a true inertial frame inside a train compartment, it is impossible to do an experiment that can tell you if you are moving or not. This is a key consequence of Newton's Laws Of Motion. However, if someone had a neutrino detector, or a Higgs detector (assuming they exist), wouldn't it be impossible to have a pure inertial frame of reference, ever, since we could always determine motion? Would this have any ramifications for special relativity or Newton's Laws Of Motion? Or, as I expect, does the train car analogy assume that nothing, not even a hypothetical bit of space-time foamy quantization, could be detected from inside the train car?