Friday, September 12, 2014

Higgs Boson Research Won't "End the Universe"

Lately a quote from physicist Stephen Hawking has been going around the Internet that, according to the media, means that the Higgs Boson could in some way end the universe as we know it. Others have gone on to suggest that such an event could be triggered in some fashion by further scientific exploration of the quantum realm, such as the sort of particle accelerator research that determined the mass of the Higgs Boson in the first place. Neither of these conjectures, though, are in any way accurate.

What Hawking meant was that the value we have now found for the mass of the Higgs Boson shows that the universe is in a meta-stable state rather than a stable one. What this means is that we now know it would be possible for the universe as we know it to suddenly end, whereas before we were not sure. Nothing scientists did changed the structure or nature of the universe; rather, determining the value of the Higgs alerted us to the (extremely extremely unlikely) possibility that the universe we live in could collapse into an unstable state.

Just as on a slope of a mountain, where there may be a little valley part way up the hill (above the real valley), it is possible that there could be little "valleys" in the energy slope. As the universe cooled, it could be that it might have been caught in one of those little valleys. Ideally, the universe would like to fall into the deeper valley below, but it could be trapped. This is an example of a metastable state.

As long as the little valley is deep enough, it's hard to get out of. Indeed, using classical physics, it is impossible to get out of it. However, we don't live in a classical world. In our universe, we must take into account the nature of quantum mechanics. There are many ways to describe the quantum realm, but one of the properties most relevant here is "rare things happen." In essence, if the universe was trapped in a little valley of metastability, it could eventually tunnel out of the valley and fall down into the deeper valley below.

This leads us to ask how the transition would occur. Would we have any warning? Actually, we'd have no warning at all. If, somewhere in the cosmos, the universe made a transition from a metastable valley to a deeper one, the laws of physics would change and sweep away at the speed of light. As the shockwave passed over the solar system, we'd simply disappear as the laws that govern the matter that makes us up would just cease to apply. One second we'd be here; the next we'd be gone.

Coming back to the original question, what does the Higgs boson tell us about this? It turns out that we can use the Standard Model to tell us whether we are in a stable, unstable or metastable universe. We know we don't live in an unstable one, because we're here, but the other two options are open. So, what is the answer? It depends on two parameters: the mass of the top quark and the mass of the Higgs boson. As we see in the figure to the right [Shown above - AQ], our universe appears to be in a metastable state, although it is quite close to the stable region. The size of the box reflects our uncertainty in our measurements.

So if we follow our understanding of the Standard Model, combined with our best measurements, it appears that we live in a metastable universe that could one day disappear without warning. You can be forgiven if you take that pronouncement as a reason to indulge in some sort of rare treat tonight. But before you splurge too much, take heed of a few words of caution. Using the same Standard Model we used to figure out whether the cosmos is metastable, we can predict how long it is likely to take for quantum mechanics to let the universe slip from the metastable valley to the stable one, and it will take trillions of years.

Mankind has only existed for about 100,000 years, and the sun will grow to a red giant and incinerate the Earth in about five billion years. Since we're talking about the universe existing as a metastable state for trillions of years, maybe overindulging tonight might be a bad idea.

I remember back when the Large Hadron Collider was being turned on at CERN, and half the alarmists out there were spouting how by various mysterious mechanisms, running a particle accelerator was going to destroy the world. What is it with these folks? They're like the fringe science version of rapture-ready Christians or something.

Nothing Hawking said implies that such a collapse could be triggered by the actions of scientists now or even far in the future with much more powerful particle accelerators at their disposal. If it were to happen, it would simply be a statistical oddity that finally came to pass without any influence from us or, really, any other particular thing in the universe. The last thing we should do is allow scary-sounding quotes like this to stand in the way of public support for scientific research and exploration.

Incidentally, a metastable universe does explain how even if the mass in the universe is such that it would expand forever according to the classical model, we could still get a repeat of the "big bang." For many decades now cosmologists have debated whether a "big crunch" will occur, in which the expansion of the universe reverses and all the matter in it is pulled back together, or if everything will continue to fly apart until some sort of final heat death renders it inert.

By definition, it means that even if the universe makes it to final heat death it cannot stay that way forever. Given infinite time, a collapse is certain to eventually occur - but by that time human beings and all other living things will probably be long gone.

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