The “negative vacuum” is an allusion to an imaginary crossover point in the aging of the universe. It’s the midlife crisis of particulate matter.
Eventually, gravity, in its perpetual tug-o-war with heat, means that most star fuel will fall together and condense, and then heat and ignite and expand, in and out and in and out in a very long explosive cycle we can think of as the many lives of a star (or nebulae, or galaxy, or universe). Big bang, little bang, everywhere a bang-bang, and each taking eons of eons, and the bigger the scale, the bigger the bang and the longer the cycle.
The “point of negative vacuum,” then, is that threshold where a given nebular region of space has crossed the line along it’s merry way between rarefied vacuum and the extreme density found at the middle of a star.
Where does “vacuum” end and “pressure” begin? Where is the point between the cold, extreme vacuum of space and the hot, extreme density of a black hole?
I have no idea.
But for us, on Earth, that point might as well be the temperature and pressure of our atmosphere. It’s something we can relate to. No, it’s not even close to being the halfway mark, but it’s something that is meaningful to us.
Call it the point where things stop sucking. Here’s to that point.