# phys: to move (momentarily) in and out of existence by extracting something from nothing

<< According to Einstein, nothing can travel faster than light in vacuum. Because of this, it is usually assumed that the Cherenkov emission cannot occur in vacuum. But according to quantum theory, the vacuum itself is packed full of "virtual particles", which move momentarily in and out of existence. These ghostly particles are usually not observable but, in the presence of extremely strong electric and magnetic fields, they can turn the vacuum into an optical medium where the speed of light is slowed down so that high velocity charged particles can emit Cherenkov gamma rays. This is totally unexpected in a vacuum. >>

Extracting something from nothing: A bright glow from empty space.
University of Strathclyde. Apr 25, 2019.

https://www.eurekalert.org/pub_releases/2019-04/uos-esf042519.php

Alexander J. Macleod, Adam Noble, Dino A. Jaroszynski. Cherenkov Radiation from the Quantum Vacuum.  Phys. Rev. Lett. 122, 161601 Apr 24,  2019.

https://journals.aps.org/prl/abstract/10.1103/PhysRevLett.122.161601