The End of Everything (Astrophysically Speaking)

by Katie Mack

Fortunately, if we need weirdness in physics, we can always rely on the quantum realm to serve us up something good. In this case, Hawking made use of the quantum weirdness of virtual particles—pairs of positive- and negative-energy particles popping into and out of existence from the vacuum of space itself.XI The idea is that this spacetime popcorn is happening all the time, everywhere, but usually it has no effect on anything because the two particles will appear and immediately annihilate against one another, both going back to being nothing again. But, Hawking said, near a black hole, you could have a situation where the negative-energy virtual particle falls past the horizon, leaving the positive-energy virtual particle so bereft that it becomes real and wanders away. The mass of the black hole would reduce a little as it absorbs that bit of negative energy, and the same amount of positive energy would appear to radiate off the black hole’s horizon. Because these virtual particles are always popping up everywhere in space, any black hole that’s not actively pulling in matter from its environment should be gradually bleeding off mass through this evaporation process all the time.