Slashdot Mirror
Black Holes Grow By Eating Quantum Foam
An anonymous reader writes "The discovery that even the most distant galaxies have supermassive black holes at their cores is a puzzle for astrophysicists. These objects must have formed relatively soon after the Big Bang. But if a galaxy is only a billion years old and contains a black hole that is a billion times more massive than the Sun, how did it get so big, so quickly? Now one cosmologist says he has the answer: black holes feed off the quantum foam that makes up the fabric of spacetime. This foam is 'nourishing' because it contains quantum black holes that can contribute to the black hole's growth. This idea leads to a prediction: that the supermassive black hole at the center of the Milky Way must also be growing in this way and at a rate that we should be able to measure. Just watch out for the burps."
we're gonna need a bigger ringworld!
Quantum foam leaving a ring around the cosmic tub?
This is a job for Doug Adams, not Larry Niven!
"Flyin' in just a sweet place,
Never been known to fail..."
Why do people equate mass with size? Because they've met your mom.
No. Those are "groupies".
"Flyin' in just a sweet place,
Never been known to fail..."
In the case of a black hole? Because the radius of the event horizon - which is one of the easiest definitions of the "size" of a black hole - grows monotonically with the mass. You can see it from Newtonian physics; if you look at the distance at which a "particle" travelling at the speed of light can't escape from a body with mass M you find it grows linearly with M. It turns out, rather coincidentally, that this coincides with the event horizon of a Schwarzschild hole, which is a black hole which is perfectly spherical (ie non-rotating), uncharged black hole.
(I went looking for a reference but I gave up quickly. Basically take Newton's gravitational law, F=GMm/r^2 for a large body of mass M and an orbiting (test) body of mass m. A particle of velocity c moving in a circular orbit is experiencing a radial force of F=mv^2/r=mc^2/r. (This is the centrifugal force, and to head of pedants, in the frame of the particle it is very much experienced even if in an inertial frame it is evidently fictional.) Equating these two you quickly find GM/r=c^2, or r=GM/c^2. This is the Schwarzschild radius.)
No, it's actually close to the exact opposite, though both are quantum effects. In loose terms, Hawking's argument is that if you generate a pair of particles just outside of the black hole (which is allowed by the energy/time uncertainty principle so long as their lifetime - before they recollide - is short enough), and one falls through the event horizon and the other escapes, then they can *never* recombine -- and then you're left with a net negative energy. That negative energy has to come from somewhere, and it comes from the black hole. Which means that the black hole radiates energy -- Hawking radiation -- and eventually will evaporate.
The argument here is quite different, although it's still a quantum effect; instead of virtual pairs here, we simply have a black hole gobbling up unimaginably small black holes that foam in and out of existence. There is no net energy loss with these, and rather than losing mass/energy, the black hole *gains* it. I'd be interested in a study seeing whether these two effects would ever balance -- I'd imagine they probably would, somewhere near the Planck scale, but that's nothing more than a speculative assumption.
Fail, off by a factor of two for the classical answer.
And first link: http://en.wikipedia.org/wiki/Escape_velocity
Frighteningly similar to Commander Crichton's wormhole weapon (save considerably slower).
With one difference though: Once you apply GTR equations, the r is twice the value you get from Newtonian calculations.
Doesn't work - the big bang is not an expansion into pre-existing spacetime. Further, it's very hard to find a way of forcing a black hole solution of GR (Schwarzschild would be the most plausible in this context) to suddenly turn into a cosmological ("Friedmann-Lemaitre-Robertson-Walker") solution of GR. What you *can* do is embed an FLRW solution inside a Schwarzschild and get a model indistinguishable from observation, but extraordinarily contrived, and indeed pointless. (Come to that I'm not fully convinced those models genuinely work because the Schwarzschild solution is static, but if you linked that with Wetterich's recent model where the "expansion" is actually a manifestation of the increasing mass of particles you could avoid that issue, too and, indeed, avoid having to embed an FLRW inside a Schwarzschild at all.)
But if you refine what you say a bit it's not very far from an idea Penrose proposed a while back but has, unfortunately, never published in detail, although he's put out some (admittedly extremely ill-advised -- Penrose is basically a genius, but knows little of either statistics or observation) papers claiming signatures on the microwave sky. Basically Penrose points out that eventually everything will evaporate to radiation one way or another: if we follow any extension to the standard model we at least open the possibility that fundamental particles can decay, and otherwise ultimately every path every particle will take will inevitably, over an infinite period of time, take it into a black hole. If there are eventually two electrons in the universe and nothing more but radiation, they will themselves inevitably collide, after an unimaginable period, with enough energy to form a black hole (remember in this scenario the electrons are constantly buffeted by radiation of ridiculously high power... even if most of the radiation is at wavelengths of, say 10m, there will be *some* photons at a vast energy and these will interact with the electrons... eventually... and accelerate them to speeds far in excess of those reached on Earth or, indeed, in the Sun). And black holes radiate. So everything becomes radiation. But for reasons that are rather technical, it is impossible within the framework of GR to distinguish between an infinite future bathed in radiation and an infinite *past* bathed in radiation, because time and length scales become rather arbitrary. Which means that through some process Penrose has never explicated - if that's a word - the ultimate future can wrap onto the ultimate past and suddenly there's a new Big Bang.
There are also other ways of getting cyclic models, which involve a bit more new physics (new scalar fields, or branes hanging near ours, etc.) but a bit less hand-waving. Indeed, there are many ways of getting cyclic universes. But Penrose's struck me as being nearest to your suggestion.
Yes, true. But like I said to the other AC who made the same (totally valid - people with mod points might want to mod these people informative, btw, so those who ignore ACs might see it) point, it's close enough for government work and it's good intuition.
But yes, both of you are right, the Newtonian calculation isn't entirely right. I should have thought a bit more carefully about what I was saying.
In astronomy, all that matters is being within a factor of 10. :P
I read TFA and all I got was this lousy cookie
Actually, it kind of fits if you bring all of the intelligent guesswork together. I read somewhere that the tiny tiny tiny black holes (possibly) created by the LHC would evaporate (due to Hawking Radiation) at an exponentially accelerating rate -- the more mass they lost the faster they would loose more, ending in a quantum sized obliterating explosion. If true, and if this new idea is correct as well, that would imply that there is a perfect point where the mass evaporation from Hawking Radiation would *just* equal the mass accumulation from consuming quantum foam. If the black hole mass starts out greater than this point then the black hole grows, less and it shrinks. Someone ought to be able to calculate (roughly?) the magical amount of mass needed to produce a pseudo-stable black hole...
The NSA: The only part of the US government that actually listens.
I'm not up on the details of contemporary physics, but it occurs to me that since the universe is supposed to have been expanding since the big bang, the overall density has decreased during that time. Does space/time and the Quantum Foam also have a density that might affect the rate at which super massive black holes could gobble it? Could conditions in the early universe encourage black hole growth/consolidation more than the current space environment?
Black hole growth via this method may still occur today, and be measurable in our own and nearby galaxies, but the rate may be so slow that it is hidden by other factors, e.g.: consumption of local stars/gas clouds.
âoeAny society that would give up a little liberty to gain a little security will deserve neither and lose both.
The background temperature of space is 2.7K, measured to exquisite accuracy (http://en.wikipedia.org/wiki/Cosmic_Background_Explorer). You might be referring to the dark energy problem, which is pretty much ill-defined, meaning we don't actually have an explanation or, indeed, even an agreement on the size of the discrepancy (which is commonly quoted as 10^120 but is actually much nearer 10^60... not that that's good.) Although you're likely referring to the string landscape, where you can get something like 10^10^100 unique vacua, or more, or maybe a few more than that, or a few more again. Which while the dark energy problem is ill-defined at least it's related - via a few assumptions, to be fair - to observation. The string landscape is entirely theoretical and relies on you accepting both string theory and the arguments that lead to the landscape - and those are much more controversial than the simple statement that the standard cosmological model does not work without a surprisingly large quantity that acts more or less like a dark energy.
Such flippant remarks... We're talking about the Earth being destroyed by laboratory professionals, and not pondering over why exactly it is we're mysteriously long overdue for an otherwise regular mass extinction event, coincidentally around the time complex life showed promise in direction of sentience. Look, they have big brains too, so why aren't the dolphins on speaking terms with us? Because they're not real dolphins.
I don't think you grasp the gravity of the situation.
One astrophysicist now claims Black Holes are made by Freaking Magic...
This comes after NuSTAR found Black Holes "wherever it looked" {my words}, ""We found the black holes serendipitously," explained David Alexander, "We were looking at known targets and spotted the black holes in the background of the images."" anywhere between 0.3 and 11.4 billion light-years from Earth. http://www.sciencedaily.com/releases/2013/09/130909154918.htm
NuSTAR http://www.nustar.caltech.edu/ and http://www.nasa.gov/mission_pages/nustar/main/index.html#.UjDw25I03n0
Now it's a race to explain this, and in the lead is Marco Spaans with mini black holes aka "Quantum uctuations in the form" that I would
tend to think would of made itself more pronounced than just adding substance to a Black Hole.
Yes, but "off by a factor of two" is considered accurate for cosmology.
And did you exchange a walk on part in the war for a lead role in a cage? - Pink Floyd.
If black holes grow by the absorbing the quantum foam, then the universe is slowly gaining mass as new matter is spontaneously being generated but not getting a chance to vanish back to where it came from. This means that eventually the cosmic expansion will halt and be reversed. This universe could end not in heat death but a big crunch. We may have the final answer in the ultimate fate of the universe if this theory is correct.
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The paper in question has specific predictions about what we should expect to see when we examine pulsars that are near black holes and moreover those predictions look like they should be testable with only slightly more advanced technology than we have now if we take the time to make the long-term observations necessary. That's the primary difference: testable, predictable results. In contrast, religion generally either fails at making novel predictions at all, or makes novel predictions generally about eschatological issues (that is end of the world) that always turn out to be wrong.
There was some concern of the hypothetical danger creation of such black holes might pose.
More concerning to me was the uninformed speculation that lead to those concerns. As one physicist quipped here on Slashdot at the time, "You misunderstand what motivates physicists. If the LHC did get sucked up by a mini black hole we would not run from the building in fear, we would run towards it with notebooks at hand".
And did you exchange a walk on part in the war for a lead role in a cage? - Pink Floyd.
It doesn't sound like too crazy of an idea to me, that these apparently precocious supermassive black holes were just left over from an earlier universe. Suppose our Big Bang erupted into a preexisting space, and these awaiting black holes significantly accelerated the galaxy-making schedule this time around. Yes, this time around.
Instead of hyperinflation expanding faster than light in the first microseconds, perhaps our Bang opened into a pre-existing "cavity" of a few light-minutes across. Perhaps we burst out of a dimple in the wall of a larger space; an ancient, nearly-collapsed universe, breathing new life into it and restarting inflation. Expansion was at purely Einsteinian speeds (is there such a term?), but an illusion was created of superluminal motion.
I've also got a theory that the acceleration of inflation is less due to mysterious 'dark energy' than to our halo of "new" matter approaching a halo of really, really old cold matter and inactive black holes that exists beyond the Hubble radius. The Great Attractor may just be a lump that is a bit closer than the rest.
Or acceleration may be due to our 3-dimensional universe passing over and through higher-dimensional topologies that are invisible to us but for their gravity. We've begun to roll downhill, for reasons of absolutely no significance, and we'll just continue to do so until things level out. The higher-dimension topologies being invisible to us, we just have to take them as we get 'em, like unexpected waves.
Why calculate when you can find it experimentally. Think of the fun!
It's not the Quantum foam's fault. It was both awful and terrific tasting until you measured (tasted) it.
Or, to quote Professor Farnsworth: You changed the result by measuring it!
My sci-fi novel, Ghost Thief, is now available from Amazon.com.
That number is called "googol", not "google".
Rethinking email
Works for NASA anyway...well...almost.
In Physics we learn that energy/matter cannot be created or destroyed, just change form, and that the universe is a closed system where the total energy/matter is static.
Recently we have also learned that virtual particles are constantly appearing and then disappearing and the void of space is not really a void but a boiling soup of virtual particles. But since these particles disaappear instantly after they appear, the net result is that the universe's energy/matter quantity does not change.
However, the idea in this article claims the opposite: virtual particles, i.e. the quantum foam, does not disappear, but it is added instead to the energy/matter of the universe, thus making the universe an open system. Isn't that a violation of the known physics laws?
"you are monopolizing, so I ask you directly."
Yeah, sorry :(
"how then can gravity escape, considering that the highs has measurable mass, in the gev range?"
The Higgs doesn't carry gravity. The Higgs field imparts mass to fundamental particles (and the Higgs boson is the particle associated with that field, though the particle itself does nothing for mass), but that is a very different thing. Quantum field theorists will describe gravity by *gravitons*, which are also bosons but where the Higgs has spin 0 -- identical from every angle -- the graviton has spin 2. The Higgs has a high mass, while the graviton is massless. Unfortunately this is itself a semi-classical picture, since these quantum field theorists have to specify a background spacetime to propagate a graviton along... utterly defeating the point if you're trying to look at this type of effect. (A massless particle would travel on the same paths as light - so a graviton in this language would evidently be trapped behind the event horizon.)
Instead when you're talking about regions of high spacetime curvature you should drop the language of gravitons and work straight with the geometry. I know a lot of quantum field theorists would mock me for that point, but I think they're as wrong as they think I am. Our best theory/theories of gravity are geometric in origin; the effects of gravity are not caused by a force but rather by curvature in the space we're traveling through. We try and go in straight lines, just those lines are curved. In this language you don't have any questions about gravity "escaping" from a black hole since there is nothing carrying gravity; it's just curvature in spacetime. A gravitational *wave* is a different thing - a ripple in spacetime - and while you'll hear people loosely talking of black holes emitting them, those waves emanate from outside the horizon. No wave will come from inside.
If we fired a Higgs into the black hole, it wouldn't come out again. However, that wouldn't do the mass of any fundamental particles in the area (things like the electron, and the quarks - protons and neutrons are not fundamental and most of their mass comes from binding energies rather than interactions with the Higgs field) because the field itself is still permeating the space outside the black hole.
Hopefully that's cleared at least one or two things up and not made it worse.
No, the reasoning is: "If P, then Q, and if not P, then most likely not Q. Therefore if Q, then most likely P."
It's the same way how you conclude that if there are footprints in the sand, that there was someone walking through the sand. If someone walked through the sand, then he would have left such footprints, and we don't know any other reasonable process which would have caused the same footprints.
Of course the footprints don't prove in the mathematical sense that someone was walking there. After all, we cannot completely rule out that for example there was someone who built a drone with foot decoy, which flew over that area and went down to make footprints as if someone was walking there. However that assumption is unlikely enough that we would usually rule it out in favour of the hypothesis that someone walked there. Of course if we later get convincing evidence that nobody walked there, or we indeed find someone building foot-decoy drones and let them fly in that area, we will probably rethink our conclusion.
If the LHC did get sucked up by a mini black hole we would not run from the building in fear, we would run towards it with notebooks at hand".
Only the experimental physicists. The theoretical physicists would ignore the black hole until their equations proved it exists.