cosmology

False Vacuum Catastrophe

Get your nerd hats ready for this one…a freakishly bizarre, totally confusing, and kinda cool possible scenario for the end of our universe.

It took me a while to get a grasp on just what a false vacuum is and just how it relates to the possible fate of our universe, and not for a second do I pretend to have a complete or intricate understanding of the concept. It’s a lot of math, a lot of abstract thinking, and a lot of quantum physics. Classical physics are the kinds of things we see everyday that make sense to us, but every year scientists are learning more and more and about the uber-tiny world of quantum physics where all kinds of totally weird shit happens. Funnily enough, it’s these tiny quantum events that may ultimately provide us with the most insight into where our universe came from and where it’s going. It may not help us with any of the whys behind our existence, but it can help us appreciate just what an astounding “thing” our universe is and just how small of a role we actually play in it.

For the record, this end-of-the-universe scenario shouldn’t be anything to get worried about.  Although it is a possibility with our current understanding, there’s really no way to know how likely of a possibility this really is.  And while generally accepted as a possible ending to reality as we know it, most cosmologists would probably hedge their bets on heat death – essentially all of the heat (energy) of the universe is gradually used up and spread so thinly as to never recombine, eventually becoming a cold, dark soup of elementary particles.  Think about it: every time you turn on your TV or make a piece of toast or radiate body heat, that’s heat that the universe will never get back.  Fortunately the universe has a lot of heat to spare, but one day it will run out; existing stars will burn out and new ones will cease to form.  Afterwards all that will remain are dense stellar remnants and black holes will remain, and then these too will use up their energy.  The fact that the universe is expanding virtually ensures this heat death.  Eventually this expansion will first rip apart galaxies, all the way down to atoms, even tearing apart protons and neutrons until nothing but massless particles are left.

Imagine a drop of red food coloring (heat/energy) in an ounce of water (the “space” in our universe).  This is an over-simplification, but stick with me.  Now one drop of red in an ounce of water is going to make a very deep red liquid – it’s a very hot universe.  But imagine this ounce of water is growing – let’s say it doubles every day (this is to represent the universe’s increasing rate of expansion).  Less than a month later – 28 days to be exact – we’d have 134,217,728 ounces of water with just that one drop of red food coloring.  Let’s turn that into a more meaningful figure: that’s about a million gallons of water, or about 1 and a half Olympic swimming pools full of water.  Just for fun, an American bathtub filled up to the overflow holds 42 gallons.  Do the math, and that’s about 25,000 full bathtubs.  So, all that water, and still that one drop of red color.  Obviously the constituents of that little drop of food coloring are still in there, somewhere, but so dilute that nothing even resembles “red” anymore.  So yeah, that’s heat death, and barring the uncovering of any great mysteries (which could certainly happen!), this is what most experts believe will happen to the universe.

But anyway, I kind of flew off topic there.  Now back to the more exotic doomsday event, the false vacuum catastrophe.  What is a vacuum?  What is a false vacuum?  It’s complicated stuff, but let’s go back to the bathtub for a workable (if over-simplified) analogy.  In any system (say, our universe) there is a ground energy state.  This is the lowest possible state for all the “energy,” which ultimately dictates our universe’s laws of physics.  If you pour water into a bathtub, it can slosh around and move, but given time, it will settle into a uniform shape, conforming to its boundaries – in this case the tub itself.  This is the ground energy state.  The water itself has no more energy; it’s at its lowest possible point.  Make sense?

Now that’s where our universe is.  It’s stable (or metastable) from this perspective.  But what if someone drains the bathtub?  There’s no way for us to know whether or not we’re in the lowest possible bathtub (a true vacuum) or if our bathtub can in fact be drained further (a false vacuum).  Even if it were drained into another container, that container could possibly be drained again.  Thus false vacuums can lead into other false vacuums, and so far, we don’t have any real way of understanding whether or not a system exists in a true or false vacuum.

So what actually happens when our universe is “drained”?  Remember that at its ground state, there isn’t any energy.  The water just sits there.  But when the plug is pulled, it starts sloshing around and flowing and releasing all sorts of energy until it settles into its next lowest energy state (a tub under the tub).  However, with a new container comes new laws of physics.  Now that the water is in a different container, it has to abide by a whole different set of laws.  Imagine that: our laws of physics turned on their head.  Maybe atoms aren’t possible in this new vacuum.  Maybe matter and anti-matter doesn’t annihilate each other.  Who fucking knows.  That’s why it’s such a big deal.  Reality – in the truest since – would be completely altered – dissolved, really, and reconfigured into something different.

This is a commonly used diagram to visually explain a false vacuum vs. a true vacuum. Notice the blue stuff. This is the “water” that is everything in our universe.

There are other concerns too besides someone “pulling the plug.”  An event with a high enough energy could topple a false vacuum into a lower energy state.  Notice that there are essentially two ways for the “water” to jump from the “tub” to something lower.  It can either be “drained” (this is a 2D diagram, but imagine a drain exiting the bottom of the false vacuum leading into the true vacuum) or “sloshed out,” over the hump.

Think of it this way: imagine all the water in the tub is connected and we drop a brick into the tub.  Water splashes out, but instead of just a few drop splashing out, it drags the rest of the water with it, out of the tub, and onto the floor.  Now we’ve reached a lower energy state, and again, everything changes. Some folks out there are even worried that experiments with particle accelerators (“atom smashers”) could potentially create such an event, but scientists find this highly unlikely due to the massive amounts of energy contained in observed natural phenomena.

So how would the water ever be drained?  It’s a process called quantum tunneling, which is pretty freaky in and of itself.  Here’s an explanation I found helpful.  If we imagine a ball rolling over a hill to the other side, classical physics says that the only way to get the ball from one side of the hill to the other is to push the ball over the hill.  However, quantum tunneling tells us that, sometimes, the ball will go through the hill.  Now this doesn’t apply to actual balls and hills, only to particles on a subatomic, quantum level.  Applying this to the false vacuum catastrophe, we see that particles can tunnel through the hump that separates the vacuums.  Like the “sloshing” example, we have to imagine that all the water is connected, and that if even one little drop tunnels through to a lower energy state, the rest will follow.

Quantum tunneling from a false vacuum to a true vacuum. Or, the bathtub being drained!

Pretty crazy stuff right?  So what can we do?  How can we know if we’re in a true or false vacuum?  Would it matter if we did?  The false vacuum catastrophe breaks down into more fanciful speculation when we get to the event itself, and in fact much of the result depend on where in the universe that the “slosh” or “drain” starts.  If we’re in a false vacuum, and if that vacuum begins tunneling into a lower energy state, it would move at or about the speed of light.  If it happened anywhere nearby (cosmologically speaking), we’d probably be blinked out of existence from one second to the next.  That little tiny bit of the bathwater that is us would instantaneously swirl down the drain and settle on the other side in some new arrangement of particles, and that’d be it.

But what if the drain was pulled on the other side of the universe?  It’s possible that, from the other side of the tub, we might just be able to see the rest of our universe “draining away” before it got to us.  That’s a killer thought: what would it look like out there?  It’s also interesting to note that if the universe expands at an infinitely increasing rate, it’ll eventually be able to outrun light – space itself will be expanding at the speed of light – so the event might never catch observers at a certain vantage point.  Obviously things get really weird at this stage of the game, and maybe that’s a good thing.  Maybe having no good answer to what would happen if a false vacuum catastrophe did happen means there’s still a lot left to understand.

I’ve offered up a really basic explanation of the false vacuum catastrophe, being careful to stay within the limits of what I can understand, but there’s a lot more to it and other, more useful implications as well.  So far we’ve been looking at a bathtub, but let’s turn that into a more 3D representation – like a bubble.  There could be bubbles within bubbles within bubbles, providing a framework for a vastly more complex multiverse.  Our own universe could contain false vacuums.  The Big Bang could’ve been the release of energy as one false vacuum tunneled (drained) into a lower energy state.  Quantum tunneling could help fill in some of the missing gaps of the Big Bang; cosmologists are pretty clear on what happened, they just can’t always piece together why it happened.

They still have a tough time explaining the large scale structure of the universe, particularly how matter is relatively clumped together instead of evenly dispersed.  Remember the red food coloring example?  The red distributes evenly throughout the water (or it will eventually) and this is sort of what scientists would expect with respect to matter and energy within the universe.  But this is not what observations support.  Instead, the red coloring is sort of clumped together in areas – blotches and strands work their way throughout the water in a noticeably thin “wall” across our container of water.  In the case of our observable universe, most of the matter is clumped together in large scale structures much like a wall – discernible height and width but comparatively little depth.  Quantum fluctuations in general have become useful in trying to determine exactly what happened in those early seconds (or fractions thereof) that ultimately dictated the distribution of matter throughout the universe.

So it’s not time to worry about false vacuum catastrophes just yet.  Earth, while only a very small part of the universe, is under much greater threats from asteroids, gamma bursts, our sun’s own evolution, and even more “local” threats like famine, disease, and war.  It is worth noting though that dark matter and dark energy continue to be two of the most poorly understood and hotly debated topics when it comes to the fate, composition, and behavior of our universe.  Cosmologists know that these things exist, but they don’t know what they are.  And of course the big question in physics is reconciling Einstein’s relativity with quantum physics, and as more physicists approach the issue, some are beginning to wonder if concepts like dark matter and dark energy might be related to our universe existing within a false vacuum.  Furthermore, continued study of the Higgs boson has revealed that it may be hanging right around the limit of what a Higgs boson in a true vacuum could support, causing some to take an even closer look at whether or not ours is “true” or “false.”

It’s amazing what scientists and mathematicians have already discovered about our universe, and no doubt that in time will continue to be upended and expanded upon again and again.  Will anyone ever be able to unearth the underlying why behind it all?  Who knows!  But just maybe we get a little closer, each and every day.

Written by The Cubist