How a false vacuum could lead to the destruction of the universe
When physicists at CERN discovered the Higgs boson in 2012 with the help of the Large Hadron Collider, they not only confirmed the last important building block of the Standard Model of elementary particle physics, which explains how particles acquire their mass (through the Higgs field, through which they move as through a viscous mass). In the process, they also measured the weight of the Higgs particle, which is 125GeV (giga-electron volts). And this is not just a number: It means that our universe is very likely in a metastable state, i.e. a state that is stable only at first glance, but can change very quickly.
Physicists call this a “false vacuum”. What does it mean? A true vacuum in this context means a region with minimal energy. Energy does not have to be zero. A real vacuum can also contain mass and energy. Only there must not be a state in which this area contains even less energy. Then it would be a false vacuum. You can easily imagine this by riding your bike up a high mountain. Arrived at the top, you let your bicycle roll. You will inevitably end up in the valley. But what if there is another mountain behind the valley, with yet another valley waiting – deeper than the one you are in right now? Your bike still has potential energy. It could roll into that deeper valley all by itself, if it weren’t for the stupid mountain in between.
So the universe is probably in such an intermediate valley. That is not yet a problem in itself. But the universe is not a bicycle. There are two ways how it can overcome the mountain. Way 1 leads over the top. A moped comes from behind and pushes you over the intermediate hill. If you just get high enough, the rest slips by itself, and you end up in the valley. Path 2 is a tunnel. Someone digs you a hole through the mountain, and you roll through. Now the universe is not made of asphalt and earth, but of quantum fields. But quanta don’t need a tunnel to move through an obstacle. Or they bring their tunnel with them, in the form of the tunnel effect, which is used among other things with transistors. So the universe could either be pushed until it can overcome the intermediate mountain – or it decides to go the way to the true vacuum through the tunnel. Of course, the universe is not conscious. The decision could be brought about by chance, the natural evolution of the universe could favor it (perhaps by a continuing supply of dark energy), or an overly daring alien (or human) in the future who creates a particularly energetic particle.
What would be the effect of the transition from false to true vacuum? The physical constants would change. Matter as we know it would no longer exist. No atoms, no chemistry. No people either, of course. How probable such a transition is, is not known today. In particular, there are still uncertainties about the mass of the top quark, which plays an essential role. Moreover, new physics, as already seen on the horizon, could overturn all current calculations. If a transition were to occur, it would spread bubble-like in space at almost the speed of light. We would notice it only when everything would be too late. Isn’t this comforting, somehow?