The coldest and densest molecular gas clouds in the interstellar medium can have temperatures of 10 K (-505 °F/-263 °C), ...

Flashes like Cherenkov radiation in space may reveal negative-energy ghosts, hinting at gaps in gravity theories.

An atom is mostly empty space, but empty space is mostly not empty. The reason it looks empty is because electrons and photons don't interact with the stuff that is there, quark and gluon field ...

(via Sabine Hossenfelder) What is empty space? In this video I summarize what physics tells us about this. What really are virtual particles? What do they have to do with the vacuum energy and can we ...