Is the universe a stable quantum system?

Is the universe a stable quantum system?

According to legend, when Damocles declared that his king, Dionysius, must have a posh and easy life, Dionysius offered to trade places with Damocles. There was only one catch. Dionysius decreed that a sword be suspended over the throne by a single horse hair, so that Damocles would always know the peril of being king. Since then the Sword of Damocles has come to represent a threat of doom that could strike without warning. While the prospect of living under a hanging sword doesn't seem pleasant, stories of impending doom are quite popular, particularly within popular science.

Every now and then some science news story will hit the press trumpeting the latest Damocles sword. Giant asteroid could wipe out life on Earth! Nearby supernova could kill us all! Solar flares could destroy civilization! Geomagnetic reversal! Rogue black holes! And on and on. The latest doomsday news to hit the press stems from a claim by Stephen Hawking that the existence of the Higgs boson means that the universe could spontaneously collapse at any moment. Game over, Man! Game over!

Like most such hype, the real story is both less sensational and more interesting. It all starts with a long-known property of quantum mechanics, that quantum systems don't always have to settle in their most stable configuration. They can instead find themselves in a locally stable state (known as a metastable state). We see this, for example, with electrons in an atom. The stable state of an electron in an atom is its lowest possible , but an electron can be in a higher energy level for a while. Eventually it can drop to a lower energy level, which releases a photon. This effect is why we see line spectra in stars and interstellar clouds.

With the discovery of the Higgs field, one question we can ask is whether the universe as a quantum system it is in a stable, low-energy state, or in a metastable higher energy state. According to the standard model of particle physics, the answer depends upon the masses of the top quark and the Higgs boson. The more massive the Higgs boson, the more likely the universe is to be stable. The more massive the top quark, the more likely the universe is to be metastable, or even unstable. From our current measurements of the top and Higgs masses, it seems that our universe is metastable.

Is the universe a stable quantum system?
Measures of the top quark vs Higgs boson masses, compared to stability calculations. Credit: Sean Carroll

If our understanding is correct, then the universe as a whole could be in a locally , but it could also jump to a lower energy state through a process of quantum tunneling. If that happened, the universe would collapse and we'd all go bye bye. So to our best understanding, it is possible for the universe to collapse. Of course by the same process it is also possible that if you run toward a wall the atoms in your body will quantum tunnel through the wall and you'll find yourself on the other side. The chances of that actually happening is negligible at best.

Of course if the were too stable, that could lead to other problems, such as the idea that we are actually just Boltzmann brains. Being metastable could actually be a good thing rather than a sign of impending doom.

So there's no need to cancel your vacation plans, or stop saving for retirement. Even if there is a cosmic sword of Damocles, the quantum thread holding it is much stronger than you might suspect.


Explore further

Should the Higgs boson have caused our Universe to collapse?

Provided by One Universe at a Time

This story is republished courtesy of One Universe at a Time (briankoberlein.com), where you can find daily posts on astronomy and astrophysics.

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Sep 10, 2014
> The stable state of an electron in an atom is its lowest possible energy level, but an electron can be in a higher energy level for a while. Eventually it can drop to a lower energy level, which releases a photon.

They make it sound as if the atom generates energy out of nothing. It doesn't. If an atom can leave the lowest energy state, it's only because it gets energy from its surrounding environment. And it can always do that as long as the temperature of the environment is not zero.

I mean, quantum mechanics is weird, but it's not *that* weird. It does comply to energy conservation.

Sep 10, 2014
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Sep 10, 2014
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Sep 10, 2014
Universe stability DEPENDS on metastable quasi states that allow constant balancing/rebalancing.

Sep 10, 2014
Perhaps Black Holes are quantum tunneling.

Sep 10, 2014
Meow! (let's see how many true nerds are here)

Sep 10, 2014
At least they're calling it a quantum system...

Jixo.
If Hawking changed his opinion 360 degrees, isn't that the same as not changing it at all?

Grondilu.
Thanks for that excellent synopsis.

Sep 10, 2014
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Sep 10, 2014
If Hawking changed his opinion 360 degrees, isn't that the same as not changing it at all?

Yep, you were upvoted for correction. But it's still possible, Hawking lives in 4D space and what we can see it's just a projection of his spin...

Making it half spin off to the left....

Sep 10, 2014
now prove we are not brains in vats, in another dimension.

Sep 10, 2014
Everything comes to an end so often. Not to be left out, I predict that a green slime big enough to consume the world, the universe, the multiverse, and maybe even Hawking's ego will do it.

Sep 11, 2014
now prove we are not brains in vats, in another dimension.

Why? This one is much more fun....

Sep 11, 2014
Jixo.
If Hawking changed his opinion 360 degrees, isn't that the same as not changing it at all?
Only the photons and phonons he uses to communicate. His electron potentials would still be precessed as they must spin 720 degrees

Sep 11, 2014
Hawking is smarter than me. But he also has difficulty communicating his ideas when speaking to the public.

He hasn't successfully communicated this one.

He's talking about a phase-change propagating at the speed of light across the entire universe from a single quantum event: a single Higgs bosun changes to a lower energy state via quantum tunneling.

Hawking hasn't explained - in lay terms - why the Higgs can't change energy states locally without triggering a phase change in the entire universe. Other particles do it all the time.

No doubt there's some abstract reasoning behind this notion of a phase change in the entire Higgs field triggered by a single quantum event. But whatever that reasoning is, it's not reaching our ears. That's a communications fail.

Sep 11, 2014
"Making it half spin off to the left..."
...and a step to the ri-i-i-i-ight!!

Sep 11, 2014
" Higgs bosun" - Raise that mass mateys! YARRR!

Sep 11, 2014
That's it, the nail is in the coffin, we're toast... I'm selling off all my investments and giving the money to... well, to commenters on this list... yes, all of you can now get a chunk of bucks!!

Just show up 1 nanosecond after the universe collapses, and pick up a check.

Sep 11, 2014
I (using very basic models) worked out the odds of tunnelling through the grate wall of china and also bouncing back of a cliff. Neither had a high probability

Sep 11, 2014
> The stable state of an electron in an atom is its lowest possible energy level, but an electron can be in a higher energy level for a while. Eventually it can drop to a lower energy level, which releases a photon.

They make it sound as if the atom generates energy out of nothing. It doesn't. If an atom can leave the lowest energy state, it's only because it gets energy from its surrounding environment. And it can always do that as long as the temperature of the environment is not zero.

What they are saying is that we may be currently in the 'excited' state. It's not that the universe would need to make a jump to an higher energy level. It would fall to a lower on.
If I read it correctly then we'd be talking about another symmetry-breaking event. And these events do tend to leave nothing untouched.

Sep 11, 2014
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Sep 11, 2014
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Sep 11, 2014
Meow! (let's see how many true nerds are here)


Awwww, I guess no one got it. I can sum up the article in five words. We are all Schrodinger's cat.

Sep 11, 2014
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Sep 11, 2014
Meow! (let's see how many true nerds are here)


Awwww, I guess no one got it. I can sum up the article in five words. We are all Schrodinger's cat.

Y'know, Tom - I just thought that was too easy to be the desired response...

Sep 11, 2014
Just wondering how you can tell if something is stable or metastable when its moving faster than light? Perhaps 100's of times the speed of light?

Sep 12, 2014
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Sep 12, 2014
So even if the universe could collapse in this manner, this would not be any stranger than the concept of the big bang, or the inability to explain qualia of consciousness, and so on. The only aspect that will give credibility (or not) is the physics behind it, not whether it is strange that the universe is on the edge of instability, or the philosophical and insurance problems with it potentially collapsing.

Sep 12, 2014
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Sep 13, 2014
Metastable states. I can't help but be reminded of self-organised criticality and the thermodynamics of extended, transient entities performing universal Church-Turning computation on the edge of chaos. Perhaps the universe is such a system, an extended-transient dissipative structure, locally lowering it's entropy at all scales by exporting it into a global environment, be it at atomic, planetary or universal scales? That entropy export process and the geometries of those flows are described by the Constructal law of Design in Nature, complimented by the Asynsis principle of how Form follows Flow.
http://asynsis.wordpress.com
http://www.scoop....l-design
http://www.scoop....ctal-law

Sep 15, 2014
if the universe would be unstable, it would have already collapsed

Sep 15, 2014
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