The anticipation among physics enthusiasts is almost palpable: In three, four days from now, December the 13th, the discovery of a rather light Higgs particle is going to be officially announced - well, at least the "observation" or whatever the official term will be. Fitting to the ‘lucky’ number 13 date, this could well spell the end of the world, literally!
According to rumors (Woit, vixra), the Higgs has been found in two different experiments, CMS and ATLAS, and both agree that it has a rather low mass. It is not fundamentally important whether the Higgs is found or not - except maybe for the so called "Higgs ether" clashing with the orthodox interpretation of Einstein relativity. Physicists have hedged their bets and made theories work either way. In fact, the Multiverse allows both to be true simultaneously. However, if the Higgs particle is below a certain threshold of mass, our best theories of our own universe will imply that the vacuum is unstable! It means that the universe decays much like a radioactive particle. Its average life expectancy depends on the Higgs mass.
The lower the Higgs mass is, the shorter the average life time. If the mass is below the threshold, which is indeed suspected to be in the same range as the discovered Higgs mass, the universe may only be expected to last a short time – we have perhaps just been lucky it did not decay yet! The Higgs has been dubbed “God particle” before. If it is really the harbinger of cosmic death, the name might be finally justified.
What worries perhaps most: The decay of the vacuum, also called “False Vacuum Decay”, can be triggered by high energy events like cosmic collisions or high energy particle experiments! The latter, so those who want to experiment keep assuring us, are far below energies reached in naturally occurring astrophysics, yet other parameters, say the density of particular types of particles involved in the experiments, may approach values that are never reached in any natural astrophysical event, at least not outside of a black hole.
If a vacuum decay is triggered anywhere in the universe, say inside the Large Hadron Collider (LHC), the vacuum will fall down into a lower energy state and thus trigger the surrounding vacuum to decay, too. A wave of destruction will be triggered, sweeping the whole universe with the speed of light, destroying everything in its way.
The details of the decay are somewhat intricate:
It has been known for about twenty years that for a low Higgs mass relative to the top quark mass, the quartic Higgs self-coupling runs at high energy towards lower values. At some point it would turn negative indicating that the vacuum is unstable. In other words the universe could in theory spontaneously explode at some point releasing huge amounts of energy as it fell into a more stable lower energy vacuum state. This catastrophe would spread across the universe at the speed of light in an unstoppable wave of heat that would destroy everything in its path. …
As it turns out a Higgs mass of 125 GeV is quite a borderline case. The situation was analysed taking into account the best recent valued for the top mass and weak coupling constants by Ellis et al in 2009. Source: vixra
Do we need to worry? Let us assume the average life time of one cubic mile of vacuum is only ten days. What would that mean? This would mean that very likely right this moment already, somewhere close to earth, the vacuum decays and a wave of destruction starts to roll through the universe. An if not, the vastness of space out in the rest of the universe would make it ‘overwhelmingly likely’ that the vacuum has already decayed some place further away and the waves of destruction are coming at us from all sides as we spea … . Ups - that was it - all over. This is not even exotic physics:
Decay of a false vacuum is an extension of a theory that’s well known in chemistry and the physics of the phases of matter. The theory applies to the different “phases” of empty space as well, and those phases are called vacua. The same physics that governs water converting to steam as you boil it applies to empty space. Kind of like when you boil water and at the bottom of the pot there are these little bubbles fluctuating, we expect tiny “bubbles” of other vacua to be forming around us all of the time.
Source: Vice– in this case about as informative and reliable as any physics website. Go figure.
What you get when searching for pictures on “vacuum” on the internet. Well, at least google has its priorities straight. This is much closer to reality than a lot of the other stuff.
So should we worry? These decays of the universe travel with the speed of light. Once they arrived, they already destroyed you. Nobody can ever observe them. On principle, nothing can observe this decay. If it traveled with only half the speed of light, we would see it coming from all sides, but since doomsday propagates as fast as light, we cannot ever see it coming - on principle - go ask Einstein.
So what happens? Nothing! In fact, the universe could as well have a 'semi-fundamental' description where any grapefruit sized part decays with an average life-time of only a millisecond. Nothing would be different. If you like, you can phrase this in Many World language and say that this is so because all the “parallel worlds”, where the universe decays, “disappear” without any observer noticing. Those parallel worlds where the universe still has not decayed, well, they still have not decayed – nothing more to say.
A God’s-eye view of what it would look like if a false vacuum bubble universe formed and detached from the “real” universe. Does not destroy the universe but could be observed and would therefore be actually dangerous! Source: Vice
Before any confusion arises: This is not wild speculation grounded on a multiverse concept. A multiverse is expected but not necessary. This issue is also not to be confused with semi-religious “quantum immortality” or say the anthropic principle. Although many will want to push this discussion under such labels, it does not fully belong there, though similarities and connections are present. All it “needs” is a proper understanding of the Many Worlds concept, which is true simply because nothing else can be consistently expressed.
Of course, a theory that did describe all physics closely according to what observers actually observe would be more satisfying and ultimately fundamental. However, physics today still deals mostly with theories that describe the universe as something that is directly really “existing” in some sense even without observers, as if it is made out of “real stuff” (which it is fundamentally not). In those theories, which are after all the best theories we have, there is no guaranty that a consistent description can be found where the universe is stable. Nothing to worry about.