False Vacuum Decay and how it applies to us or anything?

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False Vacuum Decay and how it applies to us or anything?

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If the false vacuum can decay and does, it will sweep across the universe at the speed of light and we’ll all die before we knew what hit us. So, basically nothing to worry about, if it exists or doesn’t exist.

Everything that happens in the universe happens against a zero/baseline energy. False vacuum theory is that there’s a lower zero/baseline that we can’t get to.

Imagine you have a marble in a bowl. You can rock it back and forth, spin it around, flick it, etc. It’ll rattle around in the bowl and then come to a rest at the lowest point in the center.

In our current theory of the universe the sides of the bowl are infinitely tall. That no matter how hard you hit the marble it’ll stay in the bowl and eventually settle back down to the lowest part in the middle.

False vacuum theory is saying “what if the sides aren’t infinitely tall, what if the bowel has sides of a limited height and is sitting on a kitchen table?” In this case you could knock the marble out of the bowl and it’d fall to the kitchen floor. The “zero” energy assumption was wrong, it still had gravitational potential energy that it just couldn’t release. Give it enough of a kick and it could release that energy, which in False Vacuum theory is possibly a lot of energy, enough to suck the rest of the universe over the edge of the bowl and into oblivion.

As u/revaniteanime notes – to an extent it doesn’t matter. Either it doesn’t exist, or it does and it’ll travel at the speed of light and wipe everything in its path out before anything even knows something happening.

Imagine a ball sitting on a table. The ball is *meta-stable*. That is, the ball is not in motion, but if you give it a little bit of energy to nudge it, it will roll off the table and fall, releasing its energy. The amount of energy it has to release is defined by the difference between the surface of the table and the ground.

Now, imagine an *infinite* table. You can give the ball some energy and raise it up, and push it around, but you can’t release any *more* energy than it being on the table, because it can’t fall off. There’s energy *there*, there’s a difference between the table and the ground, but because the ball can never reach the ground, that energy can’t do anything. The ball is not meta-stable, it’s just regular stable.

There is some energy in the background of the universe, in the supposedly empty vacuum of space – quite a bit, actually. Even when there is “nothing”, there is energy that manifests as virtual particles popping into and out of existence. But, like the ball on the infinite table, we’re pretty sure that the vacuum is *stable*. That energy can’t do anything.

But…what if it *isn’t*? What if the universe is only *metastable*? If so, a sufficiently energetic event might cause a portion of space to “fall off the table” and release all that energy. It could also just…happen because of quantum reasons. If that happens, the energy released would cause the space next to it to also “fall of the table” and release *its* energy, in a chain reaction that would destroy the universe as it exists and recreate it into something very, *very* different.

This *could* explain the birth of *our* universe – that there existed some form of reality which underwent such a vacuum decay, which birthed our rules of existence and our universe.

If such a thing happens, there is no way to see it or know about it ahead of time. The “explosion” propagates at the speed of light. In the very instant the light from the vacuum decay arrives, so will the decay itself. From a philosophical standpoint, there’s no point in worrying about it because there’s nothing you can do to stop it and you’ll never notice it.

The famous explanation is the ball on a hill, which is useful, but I like to start with an atom with an excited electron. Due to coulomb’s force, the positively charged nucleus attracts the negatively charged electron. It really wants to fall closer to the nucleus. The ground state of an atom is when all the electrons are as close as possible. There are no open seats for electrons to fall into. The weird thing you might think is why does there have to be a seat, can’t it just move a little closer. Surely there aren’t so many electrons that they can’t even move, right? And the answer is yes, there is a lot of empty space in the atom, but only certain energy levels are stable for the electron

This is when I like to jump back to the ball on the hill example. If the hill has a small pocket on the wall. To the left is a small hump followed by a steep downhill and to the right is a steep uphill. Shure, you could place the ball halfway up the hill, but it won’t stay there because it’s too steep. However, this little pocket is stable. If you nudge it a little to either side, it rill roll back into the pocket. But if you nudge it a bit too far, it will roll over the little hump and down the steep slope to the next pocket it encounters, or the bottom of the hill. For atoms (and the Higg’s field), the bottom of the hill is the ground state. The lowest energy it can have.

Of course you already intuitively know that all things like to lose energy. The more energy you give something, the more it has to give away, and it will do so at the earliest possible moment. Lift a ball above your head and you have given it gravitational potential energy and it wants to fall back down to get rid of that energy. Put your foot on the gas in a car and you increase its kinetic energy, but as soon as you let off the gas, putting less energy into the system, the car loses speed to friction and air resistance.

The Higg’s field may not be in the bottom of the hill, the ground state. It might be on one of those pockets halfway up the wall. Little nudges don’t move it from the pocket, but a big enough nudge might. But here’s the crazy thing, even if it takes some energy to get over that hump, since the bottom of the hill is always lower than the pocket (false vacuums are always higher energy than the true vacuum), you will get out all that energy and then some on the way to the ground state. Which basically guarantees enough energy will be released to cause the next link in the chain to also get nudged out of it’s false vacuum. A chain reaction as link after link after link falls to the ground state, propagating out in all directions at the speed of light.

No analogy is perfect, but I think that’s good enough for eli5.