# Quantum Singularities and The Big Rip **URL:** \ **Category:** Factual Questions\ **Created:** [April 30, 2008, 4:31am UTC](https://boards.straightdope.com/t/quantum-singularities-and-the-big-rip/447438 "2008-04-30T04:31:40Z")\ **Posts on this page:** 19\ **Page:** 1
**Author:** ![Enola\_Straight](https://avatars.discourse-cdn.com/v4/letter/e/dec6dc/32.png) [@Enola\_Straight](https://boards.straightdope.com/u/Enola_Straight)\ **Post date:** [April 30, 2008, 4:31am UTC](https://boards.straightdope.com/t/quantum-singularities-and-the-big-rip/447438/1 "2008-04-30T04:31:40Z")
One of the possible ends to the universe is called The Big Rip > **[Endless Void or Big Crunch: How Will the Universe End?](https://www.space.com/13393-universe-endless-void-big-crunch.html)** > > The Big Crunch, Big Freeze and Big Rip are just a few possibilities for the fate of the universe. Essentially, towards the end, all structures…starting with the galactic down to the subatomic…will be shredded apart. Can this shredding affect a Black Hole? Un-point mass a quantum singularity? ---
**Author:** ![Enola\_Straight](https://avatars.discourse-cdn.com/v4/letter/e/dec6dc/32.png) [@Enola\_Straight](https://boards.straightdope.com/u/Enola_Straight)\ **Post date:** [April 30, 2008, 4:07pm UTC](https://boards.straightdope.com/t/quantum-singularities-and-the-big-rip/447438/2 "2008-04-30T16:07:30Z")
Specifically, how does the “dark energy” affect the Schwartschild Radius? Speed up singularity evaporation with increased virtual particle pair production? ---
**Author:** ![Enola\_Straight](https://avatars.discourse-cdn.com/v4/letter/e/dec6dc/32.png) [@Enola\_Straight](https://boards.straightdope.com/u/Enola_Straight)\ **Post date:** [April 30, 2008, 9:03pm UTC](https://boards.straightdope.com/t/quantum-singularities-and-the-big-rip/447438/3 "2008-04-30T21:03:29Z")
a link to another board: [https://bbs.stardestroyer.net/viewtopic.php?t=121937](https://bbs.stardestroyer.net/viewtopic.php?t=121937) ---
**Author:** ![Enola\_Straight](https://avatars.discourse-cdn.com/v4/letter/e/dec6dc/32.png) [@Enola\_Straight](https://boards.straightdope.com/u/Enola_Straight)\ **Post date:** [May 1, 2008, 6:08pm UTC](https://boards.straightdope.com/t/quantum-singularities-and-the-big-rip/447438/4 "2008-05-01T18:08:01Z")
UltraFilter? Calmeacham? Chronos? _Anybody?_ ---
**Author:** ![Enola\_Straight](https://avatars.discourse-cdn.com/v4/letter/e/dec6dc/32.png) [@Enola\_Straight](https://boards.straightdope.com/u/Enola_Straight)\ **Post date:** [May 3, 2008, 5:17pm UTC](https://boards.straightdope.com/t/quantum-singularities-and-the-big-rip/447438/5 "2008-05-03T17:17:17Z")
last chance bump ---
**Author:** ![Enola\_Straight](https://avatars.discourse-cdn.com/v4/letter/e/dec6dc/32.png) [@Enola\_Straight](https://boards.straightdope.com/u/Enola_Straight)\ **Post date:** [May 7, 2008, 1:49am UTC](https://boards.straightdope.com/t/quantum-singularities-and-the-big-rip/447438/6 "2008-05-07T01:49:32Z")
Apparently I’m not the only one who wondered about this: > **[Big Crunch or Big Rip? Universe's Future](https://www.physicsforums.com/threads/big-crunch-or-big-rip-universes-future.161340/)** > > I remember reading some time ago that in 2001, they discovered that the speed at which the universe was expanding was accelerating. According to current models, that would mean that the universe may expand forever and maybe even rip itself apart. But... ---
**Author:** ![bonzer](https://avatars.discourse-cdn.com/v4/letter/b/45deac/32.png) [@bonzer](https://boards.straightdope.com/u/bonzer)\ **Post date:** [May 7, 2008, 10:49pm UTC](https://boards.straightdope.com/t/quantum-singularities-and-the-big-rip/447438/7 "2008-05-07T22:49:41Z")
It’s [been argued](http://prola.aps.org/abstract/PRL/v93/i2/e021102) that a black hole shrinks in the presence of dark energy. That leads to the suggestion that they shrink away to nothing as the universe hurtles into the Big Rip. All necessarily fairly speculative since we know virtually nothing about the detailed properties of dark energy. ---
**Author:** ![tim314](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/tim314/32/3468_2.png) [@tim314](https://boards.straightdope.com/u/tim314)\ **Post date:** [May 8, 2008, 1:09am UTC](https://boards.straightdope.com/t/quantum-singularities-and-the-big-rip/447438/8 "2008-05-08T01:09:22Z")
Dark energy is still not very well understood. But I don’t _think_ it’s expected that it could “pull a black hole apart”. What would probably happen is eventually all the black holes in the universe would be so far from any other matter that they’d have nothing to absorb, and then they’d gradually radiate themselves out of existence due to Hawking radiation. Some discussion [here](http://cosmicvariance.com/2006/01/26/the-future-of-the-universe/) ---
**Author:** ![Chronos](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/chronos/32/134_2.png) [@Chronos](https://boards.straightdope.com/u/Chronos)\ **Post date:** [May 8, 2008, 3:19am UTC](https://boards.straightdope.com/t/quantum-singularities-and-the-big-rip/447438/9 "2008-05-08T03:19:30Z")
One of my buddies did his thesis on this. The short answer is that we can’t really know without a full theory of quantum gravity, which we thus far sadly lack. The very slightly less short answer is that the Rip seems to be absolute, and that so far as we’re able to feebly approximate a quantum theory of gravity, the existence of quantum fluctuations appears to just make things even more extreme, not less. The long answer is about a hundred pages, most of which I don’t understand very well, either. ---
**Author:** ![Triskadecamus](https://avatars.discourse-cdn.com/v4/letter/t/b19c9b/32.png) [@Triskadecamus](https://boards.straightdope.com/u/Triskadecamus)\ **Post date:** [May 8, 2008, 4:05am UTC](https://boards.straightdope.com/t/quantum-singularities-and-the-big-rip/447438/10 "2008-05-08T04:05:25Z")
It’s also possible that the time spans we are talking about will bring up such esoteric factors as proton decay, or other things now rare to the point of near impossibility. There might be a whole lot of difference in the physics of a universe that is many trillions of years old. Consider that a post inflationary universe which experiences a big crunch, or a big rip is going to take a long time to do so, even for very large values of “a long time”. The radiative evaporation of even very large black holes is going to be accomplished in less than a few hundred quadrillion years, without considering big rips. So how old is very old, for a universe? Tris ---
**Author:** ![Chronos](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/chronos/32/134_2.png) [@Chronos](https://boards.straightdope.com/u/Chronos)\ **Post date:** [May 8, 2008, 5:29pm UTC](https://boards.straightdope.com/t/quantum-singularities-and-the-big-rip/447438/11 "2008-05-08T17:29:23Z")
Actually, **Triskadecamus** , you’re both vastly underestimating the timescale associated with a Big Rip, and vastly underestimating the timescale associated with ordinary black hole evaporation. A stellar-mass black hole (i.e., the smallest and shortest-lived ones we have confidence exist) would have a lifespan of ten to the sixty-something years. Meanwhile, Big Rip calculations suggest that a Rip could occur in as soon as a few _million_ years, far shorter than the timescale of proton decay, or even of the lifetime of the Sun. Or, of course, a Big Rip could never occur, or anywhere in between: The error bars are still pretty large. ---
**Author:** ![Ludovic](https://avatars.discourse-cdn.com/v4/letter/l/7ab992/32.png) [@Ludovic](https://boards.straightdope.com/u/Ludovic)\ **Post date:** [May 8, 2008, 5:43pm UTC](https://boards.straightdope.com/t/quantum-singularities-and-the-big-rip/447438/12 "2008-05-08T17:43:40Z")
[QUOTE=Chronos] The error bars are still pretty large. [/QUOTE] [“Clearly, there is some room for improvement here.”](http://en.wikipedia.org/wiki/Graham%27s_Number#Graham.27s_problem) ---
**Author:** ![tim314](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/tim314/32/3468_2.png) [@tim314](https://boards.straightdope.com/u/tim314)\ **Post date:** [May 8, 2008, 5:44pm UTC](https://boards.straightdope.com/t/quantum-singularities-and-the-big-rip/447438/13 "2008-05-08T17:44:26Z")
[QUOTE=Chronos] Meanwhile, Big Rip calculations suggest that a Rip could occur in as soon as a few _million_ years, far shorter than the timescale of proton decay, or even of the lifetime of the Sun. [/QUOTE] Holy crap, seriously? I don’t know why the thought of the end of the universe in a few million years freaks me out (given that we’ll all be long dead and all), but it does. I guess I always kind of figured the universe was not yet middle-aged. > [@Chronos](#): > > Or, of course, a Big Rip could never occur, or anywhere in between: The error bars are still pretty large Can you elaborate on why this is so hard to predict? I mean, I get why under the old pre-dark energy paradigm it was hard to tell if the universe would eventually collapse or expand forever. It was hard because the universe happens to be very near the boundary between those two scenarios. But now that we know the universe is accelerating, can’t we just use whatever the measured rate of acceleration is to estimate the cosmological constant (assuming that’s what dark energy is) and then use that to do some sort of approximate calculation of when the Big Rip will occur? I guess what I’m asking is: Are we still very closely balanced between some scenario in which the Big Rip occurs and some in which it doesn’t? And if not, why can’t we get a decent estimate of when it will happen? I realize any prediction would be depenent on some assumptions about how dark energy works (e.g., whether the acceleration will keep going like it has been going.) Is the problem that there are equally compelling theories about dark energy that make opposite predictions? ---
**Author:** ![Chronos](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/chronos/32/134_2.png) [@Chronos](https://boards.straightdope.com/u/Chronos)\ **Post date:** [May 8, 2008, 6:57pm UTC](https://boards.straightdope.com/t/quantum-singularities-and-the-big-rip/447438/14 "2008-05-08T18:57:09Z")
> [@](#): > > Can you elaborate on why this is so hard to predict? > > I mean, I get why under the old pre-dark energy paradigm it was hard to tell if the universe would eventually collapse or expand forever. It was hard because the universe happens to be very near the boundary between those two scenarios. > > But now that we know the universe is accelerating, can’t we just use whatever the measured rate of acceleration is to estimate the cosmological constant (assuming that’s what dark energy is) and then use that to do some sort of approximate calculation of when the Big Rip will occur? Very similar situation. We know there’s dark energy in the Universe, but we don’t know precisely how it behaves. In particular, one of the key parameters has a value close to -1. If that parameter is precisely equal to -1, then we have a true Cosmological Constant: The dark energy’s strength does not change over the lifetime of the Universe. If that parameter is greater than -1 (i.e., less negative), then the dark energy is what’s called quintessence, and its strength decreases with time. If that parameter is less than -1 (i.e., more negative), then the dark energy is what’s called phantom energy, which increases in strength with time, and eventually gets strong enough to rip everything apart. Most _a priori_ theoretical models favor the Cosmological Constant, the simplest case, or failing that, quintessence. But the current best fit to the data (at least, last I heard: These results are always getting refined and adjusted) puts the dark energy slightly on the phantom side of the line, which is why it’s drawing attention. But the error bars in that measurement can still easily accomodate a cosmological constant or quintessence. ---
**Author:** ![Triskadecamus](https://avatars.discourse-cdn.com/v4/letter/t/b19c9b/32.png) [@Triskadecamus](https://boards.straightdope.com/u/Triskadecamus)\ **Post date:** [May 8, 2008, 7:02pm UTC](https://boards.straightdope.com/t/quantum-singularities-and-the-big-rip/447438/15 "2008-05-08T19:02:45Z")
[QUOTE=Chronos] Meanwhile, Big Rip calculations suggest that a Rip could occur in as soon as a few _million_ years, far shorter than the timescale of proton decay, or even of the lifetime of the Sun. Or, of course, a Big Rip could never occur, or anywhere in between: The error bars are still pretty large. [/QUOTE] Wow. Good thing I was planning on moving, huh? 😃 Tris ---
**Author:** ![Enola\_Straight](https://avatars.discourse-cdn.com/v4/letter/e/dec6dc/32.png) [@Enola\_Straight](https://boards.straightdope.com/u/Enola_Straight)\ **Post date:** [May 9, 2008, 4:49am UTC](https://boards.straightdope.com/t/quantum-singularities-and-the-big-rip/447438/16 "2008-05-09T04:49:07Z")
Substantial replies…I love it! Anyway, if this Negative Energy is in fact some kind of force, what would its formula be? Gravity and Electromagnetism have an inverse square law, the strong and weak nuclear forces have ??? laws, how do you formulate Negative Energy? ---
**Author:** ![Chronos](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/chronos/32/134_2.png) [@Chronos](https://boards.straightdope.com/u/Chronos)\ **Post date:** [May 9, 2008, 8:43pm UTC](https://boards.straightdope.com/t/quantum-singularities-and-the-big-rip/447438/17 "2008-05-09T20:43:17Z")
> [@](#): > > Substantial replies…I love it! > > Anyway, if this Negative Energy is in fact some kind of force, what would its formula be? > > Gravity and Electromagnetism have an inverse square law, the strong and weak nuclear forces have ??? laws, how do you formulate Negative Energy? The stress-energy tensor of dark energy is proportional to the metric. Matter which has no pressure or other stresses on it (what relativists call “dust”) has a stress-energy tensor that looks something like ```auto rho 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 ``` This is an excellent approximation for most “ordinary” matter one would encounter, since (in appropriate units) most pressures one encounters in everyday life are negligible compared to the energy densities encountered. If you have some sort of fluid for which the pressure is not negligible, such as the material of a neutron star, you’ll instead have a stress-energy tensor like ```auto rho 0 0 0 0 P 0 0 0 0 P 0 0 0 0 P ``` where P represents the pressure, and there is typically some sort of relationship (called the “equation of state”) which relates rho (the energy density) and P (the pressure), but even for things like neutronium, the P is always positive. You can also have more complicated materials where the three pressure terms are not all the same, or which have off-diagonal terms, but those materials aren’t fluids. Well, with the dark energy, not only is the pressure comparable in size to the density (equal in magnitude, in fact), it’s also negative. That is to say, the equation of state for dark energy is P = -rho, and its stress-energy tensor looks something like ```auto rho 0 0 0 0 -rho 0 0 0 0 -rho 0 0 0 0 -rho ``` The dark energy then interacts according to the same laws of gravity as anything else. The catch is that gravity isn’t based only on the energy density, but on the entire stress-energy tensor. We can usually get away with only considering the energy density, since (as mentioned) for most situations, that’s far greater than any stresses, which results in an attractive force of gravity. But the pressure also contributes, and for dark energy, it’s not negligible any more. In fact, since the pressure is just as large as the density, but there are more pressure terms than density terms, for dark energy the pressure actually ends up being more relevant. And since the pressure is negative, the force resulting from dark energy (which, again, is a perfectly valid gravitational force) is repulsive. As for scaling, it ends up (though I won’t try to demonstrate it here) that the force resulting from the dark energy is directly proportional to distance. ---
**Author:** ![Exapno\_Mapcase](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/exapno_mapcase/32/1051_2.png) [@Exapno\_Mapcase](https://boards.straightdope.com/u/Exapno_Mapcase)\ **Post date:** [May 9, 2008, 9:56pm UTC](https://boards.straightdope.com/t/quantum-singularities-and-the-big-rip/447438/18 "2008-05-09T21:56:46Z")
Six posts at the beginning of a thread! Is this the all time record? ---
**Author:** ![tim314](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/tim314/32/3468_2.png) [@tim314](https://boards.straightdope.com/u/tim314)\ **Post date:** [May 11, 2008, 6:44am UTC](https://boards.straightdope.com/t/quantum-singularities-and-the-big-rip/447438/19 "2008-05-11T06:44:47Z")
Kudos to **Chronos** on the detailed answers. “Kudos to Chronos” would be a cool name for a band. (Well, for certain definitions of cool.) 🙂