Negative Mass in sound waves
2019-03-12 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 non-relativistic limit. And, finally, it is not a quantum effect, because the formalism of  applies unaltered to classical waves.
Gravity is freaky.
2019-03-12 at 3:18 PM UTCRelativistic quantum mechanics.
2019-03-12 at 5:10 PM UTC
Originally posted by -SpectraL Relativistic quantum mechanics.
2019-03-12 at 7:06 PM UTC
2019-03-27 at 9:56 PM UTChttps://www.caltech.edu/about/news/levitating-objects-light
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.