If the EMdrive works, physics falls apart

But if the EMdrive is truly reactionless, then Newton is wrong. Also, Einstein is wrong, Maxwell is wrong and all of quantum physics is wrong. There’s a fundamental symmetry that causes momentum conservation: translational symmetry. It means that if my system is over here, at a certain point in space, it should obey the same laws as if it’s over there, at a different point in space. But if momentum conservation isn’t truly fundamental, then translational symmetry cannot be a good symmetry of the Universe. In other words, there must be a preferred location, where the laws of physics are different in one location than others. The laws of physics, all of a sudden, depend on position.

It means that the fundamental principle of relativity is wrong. It means that if you’re in an inertial reference frame, you can see an entire system’s momentum change over time. Moreover, it means that observers in different reference frames will see violations of momentum conservation by different amounts. If you violate momentum conservation by different amounts, you violate energy conservation, too; energy is not only not conserved, it’s not conserved by different amounts in different reference frames. The most sacred law of particle physics — one that has been observed to apply to every system and every interaction set in history — would be busted.