User Controls
Negative Mass in sound waves

20190312 at 3:05 PM UTC
Thus, in a very physical sense, the phonon carries (negative) mass. Moreover, this is not due to the usual equivalence of mass and energy in relativity: the effect survives in the nonrelativistic limit. And, finally, it is not a quantum effect, because the formalism of [1] applies unaltered to classical waves.
https://arxiv.org/pdf/1807.08771.pdf
Gravity is freaky. 
20190312 at 3:18 PM UTC

20190312 at 5:10 PM UTC
Originally posted by SpectraL Relativistic quantum mechanics.
https://en.wikipedia.org/wiki/Relativistic_quantum_mechanics
Pythagorean theorem
https://en.m.wikipedia.org/wiki/Pythagorean_theorem 
20190312 at 7:06 PM UTC

20190327 at 9:56 PM UTChttps://www.caltech.edu/about/news/levitatingobjectslight
Related, but still theoretical. There is a MUCH better way to levitate things using light than what they're proposing. The government doesn't want to allow that of course.