>>12298028Light travels slower in the atmosphere because it bumps into particles, gets absorbed and then released. Space doesn't really have particles, so light goes as fast as it can.
Does the whole "true" vacuum thing refer to the fact that empty space still has energy, and is at a local minimum rather than a true minimum? The pop sci scare was that, given enough energy, we can push space out of its local minimum and into a true minimum, which would release a lot of energy and cause the same thing to happen to nearby space, in a bubble expanding outwards at light speed. The problem is, the resulting "true" vacuum may have entirely different physics, which would mean we can't exist within it.
