The universe may be a false vacuum bubble
Why is there something instead of nothing and how long will that something last?
Why is there something instead of nothing and how long will that something last?
The question of how the universe came into being is one of the most difficult unanswered questions of physics (and meta-physics). Did the universe emerge from a black hole in another universe? If so, where did that universe come from? Is it turtles all the way down?
Another option is that the universe is, in some sense, in a temporary state and what we think of as reality is what is called a false vacuum.
A false vacuum occurs when a field has two “ground” states, one higher than the other. You can think of the false vacuum as being like a valley. On all sides of the valley are mountains and for anyone in the valley, it seems like the lowest possible place to be. Yet, unbeknownst to those in the valley, on the other side of the mountains is a sheer drop to the sea. In this case, the sea is the true vacuum, the lowest ground state of energy, and the false vacuum only gives the impression of being the lowest state because everything right around it is higher energy.
In classical field theory, there is no way for something to get out of such an energy valley unless you apply some random external energy that lets things evaporate out of it, but, if your valley contains the sum total of all things that exist, then there is no way to apply external energy. Thus, everything should stay put.
In quantum field theory, on the other hand, nothing is certain, and in fact a field or particle’s uncertainty as to its state will allow it to slowly leak out. You can imagine quantum mechanics adding an underground river under our valley. While things generally stay put in the valley, over time the river will carry pieces of the valley away until the valley caves in and all flushes out to sea.
This is the problem of the false vacuum and it may pose an existential threat to, well, everything. If true, it could affect not just the evolution of our cosmos over time but actually pull everything down to the ground state, including all matter. Everything from quarks and electrons to protons, neutrons, atoms, and molecules would disintegrate into nothingness, as if they were never there.
The word for this is that the universe is metastable. It is in a kind of resting place like the saddle on a horse, but it could easily slide off sideways and end up flat on the ground never to rise again.
We know that metastable processes exist in the universe. An example is called gravothermal collapse where a star cluster of many stars buzzing like a swarm of flies collapses from a metastable state into a smaller, hotter, faster cluster with excess peripheral stars being cast out into the abyss. Happening over a stage of lightyears, such a collapse is inevitable in the complex dynamics of so many gravitating bodies and requires no quantum decay. Nevertheless, such clusters can persist for aeons without undergoing such a collapse.
Physicists assure us that the order of time over which matter is likely to endure in the case of a false vacuum is probably tens of billions of trillions of years, vastly longer than the age of the universe. Then again, it is possible that it is only tens of billions of years (the universe is “only” about 13.7 Byrs old) . We just don’t know.
Probability would suggest that we are likely to have evolved at a point when the universe is most favorable to life. This is a Bayesian argument (an argument about what we think is probable) so take it with a grain of salt, but if that is so then does it suggest that the universe is likely to be hostile to life in the next several billions of years? Perhaps even in the process of a complete collapse into a ground state? Such a death would annihilate not just galaxies but drag matter itself into nothingness.
One is reminded of the Great Nothing in The Neverending Story, swallowing up everything into nonexistence.
We also know from quantum mechanics that metastable states (false vacuums) can exist when a unified quantum field theory breaks down into several separate forces. Since we believe that there was a unified force at the time of the Big Bang, there is no guarantee that it broke down into its lowest ground states. Rather, it may have decayed into a false vacuum such that we perceive fluctuations around that false vacuum as particles. It is also possible that the universe, once in that valley, has stayed there.
In the words of Michael Turner and Frank Wilczek who published a paper in a 1982 issue of Nature on this idea,
[W]ithout warning a bubble of true vacuum could nucleate somewhere in the universe and move outwards at the speed of light, and before we realize what swept by us our protons would decay away.
This may have already happened somewhere in the universe and is speeding towards us in an expanding bubble of nonexistence.
If you’ve ever tried to boil water in a microwave, you have seen something like this happen. When the microwave boils the water, the water below the surface wants to turn into steam, but to do so it requires nucleation sites where bubbles can form. Otherwise, it becomes superheated liquid water, prevented from evaporating by the smoothness of the mug and the lack of any external vibration to shock it out of its metastable state. As soon as you place something in the water like a tea bag, the superheated water will nucleate around the bag’s irregularities and turn to steam. Those bubbles will encourage other bubbles to form causing the whole thing to froth and steam even when no additional heat is applied. (If there is enough superheated water, it could explode.)
Thus, with the universe, one bubble of true vacuum would be enough to cause the universe to boil itself into nothing.
Turner, Michael S., and Frank Wilczek. “Is our vacuum metastable?.” Nature 298.5875 (1982): 633–634.