New Preliminary Evidence Points To A Universe-Ending Big Rip
The theory that the Universe can end disastrously in a “Big Rip” has received some preliminary theoretical support.
The Big Rip scenario in which the universe, including every tiny piece of it, rips itself apart in the distant future has been bandied about for quite a while now ever since the ever-increasing expansion of the universe was discovered in 1990s. This expansion was likely due to some weird sort of negative pressure or anti-gravitational energy which is now-famously referred to as Dark Energy. As End-Of-The-Universe theories go, this one was certainly at the extra-terrifying end of the spectrum. I did feel better though when I read consistent scientific assurances that this horrific end-game was highly unlikely.
Now, some scientists are not so sure again.
This latest theoretical go-round owes its chops to something called cosmological viscosity. When I think of viscosity, I think of molasses. Its high shear viscosity means that its movement is inhibited at the molecular level, causing it to flow only very slowly from one place to another. At the other end of the spectrum is a low viscosity fluid like oil. It so easily spreads, that a drop of it on water can quickly thin itself out to a thickness comparable to the wavelength of light. This means that light can bounce off its top layer and its bottom layer. Those two wave-trains will then have their waves out of sync (since the bottom-reflecting light traveled a little bit farther) creating one of the most beautiful phenomena in nature, thin film interference or PLPC (Parking Lot Puddle Colors). I just made that acronym up btw.
You can now disregard what I just said because Cosmological Viscosity is very different. It refers to Bulk Viscosity (resistance to expansion or contraction) rather than Shear Viscosity (resistance to flow). Water then would have a high bulk viscocity since it is essentially incompressible while air would have a low value since we can compress the shit out it.
Apparently, this concept of bulk viscosity can be applied to larger scales, specifically, the matter within the entire universe (which can be thought of as a pressureless fluid). In order to explore this concept, assistant Professor of Mathematics Marcelo Disconzi (Vanderbilt University) and his colleagues looked at relativistic fluid dynamics or what happens to fluids when they approach significant fractions of the speed of light. To do this they examined supernovas and neutron stars which can create such phenomena. This type of analysis has been problematic in the past because when they theoretically accelerated realistic fluids, all sorts of weird results appeared like the potential of the fluid to travel faster than the speed of light.
In the parlance of physicists, those results are chiroptera-excrement insane (bat-shit crazy). To properly solve these relativistic fluid dynamics equations, Disconzi reconfigured them specifically to deal with the nonsensical faster-than-light results. Once he did this, he and his partners took their shiny new equations and applied them to the wider ranging theories of Cosmology. It is here that they noticed surprising support for a scary interpretation of Dark Energy and the fate of the universe itself.
Dark Energy is probably familiar to many of you. I’ll describe it more anyway.
The term is actually a place holder for arguably the biggest mystery in the universe. In 1998 when it was discovered that the universe was expanding at an ever-increasing rate, they had no idea what could causing such a thing. It was probably some kind of negative-pressure energy pervading the universe but not much more than that was known. They threw the “dark energy” label at it to reflect this ignorance.
Our theories have evolved in the interim but huge questions remain unanswered. Most of the formulations of Dark Energy do not include the concept of bulk viscosity even though they share some of the same “repulsive” characteristics. Those few earlier models that did include viscosity did not point to a Big Rip. This latest formulation though removes a pre-existing theoretical barrier to the Big Rip and actually nudges the universe right into that worst-case-scenario. Therefore, the authors think it’s worth further pursuing this idea that viscosity may play a significant role in Dark Energy and thus the expansion of the universe.
Not just the expansion though. It may have a hand in the end-game of the universe itself, making it messy as hell.
This all depends on the true nature of Dark Energy though:
If Dark Energy is equivalent to the cosmological constant then we’re probably ok. Einstein famously came up with this constant when he realized his General Theory of Relativity predicted an expanding universe. Sure, we all know today that the universe is expanding but back then everyone believed fervently that the universe was static. So strong was this belief that Einstein simply assumed his theory was wrong (or perhaps incomplete) in that regard. He added a “fudge factor” to the theory (the cosmological constant), an outward pressure or energy density to balance the inward gravitational pull, creating a static universe. Of course, when Hubble discovered that the universe was indeed expanding, Einstein said “D’oh!!” (in German) and called it the biggest mistake of his life. When Dark Energy was discovered, the idea of this constant was resurrected to describe the energy density of the universe that could explain this repelling nature of the universe. This constant though was only the simplest possible type of Dark Energy. By definition, it does not change in space or even over time.
Another type of potential Dark Energy is called Phantom Energy. This variant is dynamic. It changes over time in a way that makes it more powerful and pernicious than the cosmological constant.
Will the real Dark Energy please stand up?
So which type is the real one? We don’t know, but if the researchers are correct about Bulk Viscosity (a big IF at this point), then the evidence could point towards Phantom Energy.
So what? So the universe expands a bit faster than we thought. What’s the worst case scenario?
It’s called the Big Rip and it could make your toes curl (right before they fly apart).
In this scenario, the expansion of the universe decreases the size of the visible universe relatively quickly until one atom in your body can never even see its former neighbor atom again because it’s beyond the cosmic horizon. This is happening all the time, albeit in a more relaxed way. As the universe expands, there is essentially more space between you and any other astronomical object (that’s not gravitationally bound to us). The farther away something is, then the faster it appears to recede from us because there is more expanding space between us. Over gargantuan distances, this recession can even exceed the speed of light. No worries though, this doesn’t break Einstein’s law that nothing can exceed the speed of light because it is space/time itself that is actually doing it. This creates a bubble of sorts in the universe. Anything within that bubble can exchange information with everything else in it because space isn’t expanding so fast that light can’t go from one end to the other. This is the observable universe. Anything outside that bubble however is receding faster than light so there’s no way for its light to reach us since it can never outpace the expansion of space separating us. As time passes, space and stars that were near the edge of the bubble, cross this horizon due to the continued expansion, forever leaving our observable universe. In this sense, the visible universe is getting smaller and smaller.
If the researchers are correct and Phantom Energy holds sway, then this shrinking universe will continue to shrink, but at ever faster rates until, at the very end, it goes into nutso overdrive.
This is what our robot descendants could potentially experience in about 22 billion years:
- Towards the end, our observable universe will seem ok since the light from its edges will have already travelled a good portion of its journey towards us. The bubble though will be closing in much faster than it used to, unbeknownst to us
- 60 million years before the Big Rip, our nearest neighbor galaxies and even the Milky Way (or whatever it has evolved into) will begin to rip apart
- A few months before the end, the earth (or the planet constructed to replace it) will be pulled away from the sun (more precisely, the white dwarf that used to be the sun)
- With 30 minutes left, the “earth” will be ripped apart
- At t-minus 10 to the -19 seconds, molecules are shredded and then the constituents of the atoms themselves
The universe as we know it would be over. Our brief epoch of “Structure” would be replaced by something else with each of the minutest particles inhabiting its own little observable universe. No stars, no planets, no life, no Reese’s Peanut Butter cups.
Still, I wouldn’t worry too much about this…yet. This was published in the journal Physical Review D earlier this year. I haven’t been able to find any evidence that it has generated much interest in scientific circles and the article has yet to produce any citations on the publishers website. The authors themselves admit at the end of their paper that:
“…a single fluid with viscosity could account for both dark matter and accelerated expansion, although the latter idea faces severe difficulties”
Yes, there has been quite a flurry of articles published recently about this on the popular-science news sites but why now? It may well be the result of an act of desperation by those heavily invested in the theory which is never a good sign. Let’s see what other scientists in the field have to say about it. I’ll be on the look-out.
In any case, even if the authors are spot on, we do have 22 billion years to get our shit together.
Publication: Marcelo M. Disconzi, et al., “New approach to cosmological bulk viscosity,” Physical Review D 91, 043532, 27 February 2015; doi:10.1103/PhysRevD.91.043532
Featured Image: http://sci-techuniverse.blogspot.com/2015/07/new-cosmic-model-favors-big-rip-demise.html
Observable Universe: https://theskyisbeautifultonight.wordpress.com/2013/01/28/the-size-of-the-universe/