Original version With this story appeared in Quanta Magazine.
Vacuum collapse, the process that could end the universe as we know it, could happen 10,000 times sooner than we expect. Fortunately, it won’t happen for a long, long time.
When physicists talk about “vacuum” the term sounds like it refers to empty space, and in a sense it does. More precisely, it refers to a set of default settings, like the settings on your control panel. When the quantum fields that permeate space are left at these default values, space is considered empty. Small changes to the settings create particles—turn up the electromagnetic field a little, and you get a photon. Large changes, on the other hand, are best thought of as entirely new default settings. They create a different definition of empty space, with different characteristics.
One quantum field is unique in that its default value can change. Called the Higgs field, it controls the mass of many elementary particles, such as electrons and quarks. Unlike all the other quantum fields that physicists have discovered, the Higgs field has a default value above zero. Increasing or decreasing the value of the Higgs field would increase or decrease the mass of electrons and other particles. If the Higgs field were set to zero, these particles would be massless.
We could stay with the default non-zero setting for all eternity if not for quantum mechanics. A quantum field can “tunnel”, jumping to a up-to-date, lower energy value even if there isn’t enough energy to get through the intermediate higher-energy settings, an effect similar to smashing through a solid wall.
For that to happen, you need to have a lower energy state to tunnel into. And before the Immense Hadron Collider was built, physicists thought that the current state of the Higgs field might be the lowest. That belief has changed.
The curve that shows the energy required for different settings of the Higgs field has always resembled a sombrero with the brim up. The current setting of the Higgs field can be visualized as a ball resting on the bottom of the brim.
Illustration: Source: Mark Belan for Quanta Magazine