You might think the universe is stable. From our tiny perspective, things seem calm and stable. But from a higher picture, nothing really is.
The universe we know started 13.8 billion years ago with a big, sudden bang. Just like an expanding balloon, the universe inflated from a size smaller than an electron to nearly its current size within a tiny fraction of a second. Instability existed since the beginning of the universe.
But what kickstarted it? No one knows.
The observable universe appears to be expanding as if it came from a single point, but nothing is for sure. For all we know, the universe may be infinite. It could exist before the big bang.
And what caused this inflation? Still, no one knows.
And we don’t even know whether inflation is even the correct theory. Hey, don’t get me wrong on that, I’m not saying it’s the wrong one either.
Even though theories are all we have at the moment, human nature does not like not knowing. We want to know, and we want to get somewhere. We learn and grow thanks to a very important feature that we possess. Curiosity.
It seems humans take the whole universe for granted. In reality, we could be living in a false vacuum. The idea of a false vacuum arises from the quantum mechanical principle of uncertainty proposed by Heisenberg in 1926.
It is possible that the vacuum of space we observe throughout the universe is not the lowest possible state of energy for a vacuum, meaning it is possible for everything to collapse into a true vacuum. This, in turn, means the universe could burst just like a water bubble. Wow! What happened here?
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Anyways… What is a true vacuum?
A true vacuum is supposed to be devoid of everything. But as far as we know, this isn’t possible. And that’s because quantum theory says energy fluctuations known as virtual particles are constantly popping in and out of existence. That means pairs of quarks and anti-quarks called virtual particles can arise from the energy of the vacuum, annihilate, and radiate back. In this scenario, the current vacuum is metastable. Stable means the state of material is truly unchanging, whereas metastable talks about the state of matter where a change cannot be observed because the changing is too slow to be observed.
If the universe is metastable, then what appears to be stable now could quickly worsen if something were to go wrong.
Our false vacuum universe could easily tunnel into the true vacuum at any moment. But since it hasn’t done so in almost 14 billion years, you can still go out there and enjoy the beach.
In the false vacuum theory, which is part of the quantum field theory, the fundamental objects of nature are not particles but fields. Particles are unit excitations of these fields, and the lowest energy state of a field is when it has no excitations at all. This would be the vacuum with no particles in it, which is not the case in the universe we live in.
Photons, for example, are excitations of the electromagnetic field. It takes a tremendous amount of energy for the photon to even exist. If there is no photon, then there’s no excitation in the field.
Aspects of the Higgs boson suggest that our universe is only “marginally stable”, or is perhaps in a transition phase to a more stable state that would result in a universe with fundamentally different properties.
Living in a universe where our matter is fundamentally unstable means particles like the electron, a neutrino, or the photon may eventually decay to a more stable state. That’s what we call false vacuum decay.
It would take energy to make the current false vacuum go down to its lowest possible energy state. The false vacuum state could exist for billions, or trillions of years.
If it dropped to a lower energy state, a true vacuum bubble could form in our universe, endlessly expanding at light speed. We are not sure what that would do, but it would probably change the laws of physics, constants, etc. It would annihilate everything in its volume, meaning all we know would cease to exist in an instant. That could go on until nothing is stable anymore. Maximum entropy, complete chaos, no more work to be done, things become cold and dead.
But maybe this can’t happen simply because it can’t be observed or measured. Vacuum decay would destroy anyone or anything that could observe the results.
However, the false vacuum is a result of the Standard Model of particle physics, a model which we all know is incomplete. The probability of vacuum decay is so small that in every practical sense there is no chance of this happening.
But keep in mind that there’s so much more that needs to be known that our whole understanding of reality could one day change.