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Every Black Hole Contains a New Universe

203 points by robg 14y ago

cft 14y ago
In Einstein's theory of general relativity, Riemann tensor is assumed to be symmetric, due to great simplification of the theory compared to the one with non-symmetric Riemann tensor, and an absolute lack of experimental evidence to the contrary for 100 years since it was discoveried. Torsion, which is the cause of asymmetry of the Riemann tensor is set to zero. I do not know why this author is so excited about torsion tensor, the idea that torsion could be non-zero has been around for at least 90 years, but got zero traction. Disclaimer : I have a phd in string theory.
- taliesinb 14y ago
  I don't have a PhD in string theory, but would like to make the point that many times in the history of science ideas that were originally regarded as uninteresting lie dormant for a long time only to usefully surface much later in the context of new evidence. In this case, the researcher seems to be excited specifically because of the potential of torsion to explain dark energy -- a recently discovered phenomena (although of course, oddly presaged by Einstein's cosmological constant hack).
  - cft 14y ago
    The classical theory of gravity with torsion certainly does not explain dark matter. The author is trying to build some quantum theory of gravity, where torsion is required, speculating that it would explain dark matter. I should add here that the attempts to build a quantum theory of gravity without torsion failed in the last 100 years (string theory is the best candidate), and the author is trying to add even more complexity by adding torsion tensor.
    - silentOpen 14y ago
      Complexity or model? Torsion is biplanar directed? We know quantum constants. Is a cosmological bivector so different? Should be observable? If only we could measure universal expansion accurately at small timescales, we could listen to the rain on the roof (horizon).
    - DeepDuh 14y ago
      I'm trying to follow you as a (very interested) layman, so excuse me if I'm being stupid. Couldn't the failure to build quantum gravity be BECAUSE torsion has been excluded (which is I believe what the author suggests)? Maybe this is something that has to be looked into. I'm thinking that a marriage of physics, mathematics and CS might be necessary to overcome our limits in understanding these structures. Something like an IBM Watson for physicists, where a computer is fed with all informations we have and solves an optimisation problem to come up with a unified theory explaining all the phenomenons with the least complex solution (i.e. the least universal constants). Another requirement would be to have 42 as an error code for all possible failures in the calculation ;).
    - guscost 14y ago
      Dark matter is an explanation!
    - vorg 14y ago
      The author paraphrases "spacetime tells matter how to move, and matter tells spacetime how to curve". The torsion axiom extends this to "...and matter tells spacetime how to curve and twist". The way he explains it makes it sound like an elegant way to complete the General Relativity hypothesis, which Einstein described as "the happiest thought of his life". If an axiom has a certain elegance about it, then perhaps a quantum theory of gravity without torsion is adding the complexity, not the other way around.
  - jopt 14y ago
    Don't forget confirmation bias. Most dormant theories are dormant for a reason.
- Steuard 14y ago
  Mind you, string theory itself includes torsion: the Riemann tensor that arises in (e.g.) curved backgrounds includes contributions from the NS-NS B-field that correspond precisely to the effects of torsion. I don't think that non-zero torsion in itself is an outlandish idea, but I completely agree that it's fair to be skeptical of claims that torsion has significant observable effects. Disclaimer: I also have a PhD in string theory.
  - partagas 14y ago
    >Mind you, string theory itself includes torsion I'm not sure I understand. In Riemannian geometry it might be convenient to use a connection with non-vanishing torsion, but it is not required. What do you mean by 'includes'?
    - Steuard 14y ago
      Well, to give an explicit example (sorry, non-specialists!), consider the nonlinear sigma model action for superstring theory in an arbitrary background geometry (that is, arbitrary spacetime metric G and NS-NS B-field; we'll ignore the dilaton). The coefficient of the 4-fermion term is the Riemann tensor. But if you construct that Riemann tensor just from the metric (as one does in general relativity without torsion), you'll omit essential pieces: you also need to include terms in the Riemann tensor resulting from a non-zero torsion tensor T=-dB (in differential form notation). A similar situation holds for the covariant derivatives in the fermion kinetic terms. Now, it's entirely up to you whether you write that 4-fermion term coefficient as "Riemann tensor (including torsion)" or as "Riemann tensor (torsion free) + (lots of weird, arbitrary-looking interaction terms involving derivatives of B)". So on some level, there's no reason that you must use a connection with non-vanishing torsion. But I would claim that the equations are much more elegant (and give deeper insight) when expressed with torsion "built-in". [Fun fact: So does Polchinski, but he's not talkative about it. If you look up "torsion" in the index of Vol. 2, the first reference is to the page with the equations I've referenced above... but the word "torsion" doesn't appear anywhere in the text of the page!] Aside: If anyone out there is interested in how this torsion stuff fits into the mathematics of Relativity, you might have a look at my notes on how it would be incorporated into Bob Wald's textbook: http://www.slimy.com/~steuard/teaching/tutorials/GRtorsion.pdf http://www.slimy.com/~steuard/teaching/tutorials/GRtorsion.p...
taliesinb 14y ago
Of course headlines have to be catchy, but this universe-in-a-black-hole concept is hardly a new one. Rather, the novel part here seems to be the idea that the connection in GR might might possess non-zero torsion, contrary to what is normally assumed. In the whole black-holes-create-universes vein, last century the theoretical physicist Lee Smolin presented the quite delicious idea (described in his book The Life Of the Cosmos) that entire universes might be subject to the process of natural selection. This would work if singularity formation involves the transmission of physical constants to the 'daughter' universe with slight modification, quite a thing to suppose given we don't really know what physical constants 'mean'. If it occurred, this natural selection would optimize these constants for the production of black holes, which luckily for us co-incides with the production of life-bearing stars. Of course, all very unfalsifiable, but kinda epic.
- dalke 14y ago
  One SF short story takes this further. The best form of interstellar travel generates black holes, so the universe is optimized for producing the type of life which does interstellar travel via that process. No need for coincidences here, and even more un-falsifiable.
  - ctkrohn 14y ago
    What's the name of the short story? Sounds like it could be interesting.
    - gliese1337 14y ago
      Not sure about a short story, but there's a novel with that idea: Learning the World: a Scientific Romance by Ken MacLeod
      - pavel_lishin 14y ago
        Gregory Benford also wrote a novel that touches on this topic called "Cosm", which is a pretty excellent read.
charlieflowers 14y ago
Perhaps this helps explain Fermi's paradox (at least partly) ... some of the many, many aliens we should have found by now might be living either out in the parent universe, or inside other black holes in our universe. I'm way out on a limb here, but it's an interesting speculation. Whadda you think?
- tuxcanfly 14y ago
  Fermi's paradox would still hold for this universe, methinks.
  - jeffool 14y ago
    Yeah, but there could be a new parenthetical, "likelihood of an alien living in another universe, multiplied by all the effects of Fermi's Paradox itself, and multiplied by the likelihood of that alien's ability to traverse universes."
    - mokus 14y ago
      I think that would be a very small extra factor, especially if you also add the likelihood of that alien's interest in traveling to specifically this part of this universe. And of course, we have no reasonable basis for estimating any of those numbers. We have a sample size of one universe and we don't even know the rate of occurrence of life in that one. Still, it can be fun to speculate.
- prawn 14y ago
  I don't think so because all the elements being plugged into the Drake Equation (for example) exist within our universe and not in any parental or child universes. In fact, the Drake Equation only speaks of potential life in our galaxy rather than the next step beyond that. The estimates relating to the paradox all come from what we've understood to be around us - galaxies, stars, planets, etc. (IANA anything of any consequence to this discussion - just an eager reader!)
- entropy_ 14y ago
  I don't think it helps much to explain Fermi's paradox since the estimation there is based on the size of the universe. If it turns out that the universe is massively bigger then so should the estimate of how many alien civilizations there are be.
ygmelnikova 14y ago
"You're very clever, young man, very clever," said the old lady. "But it's turtles all the way down!
Porter_423 14y ago
That is quite intriguing.
cwzwarich 14y ago
Will theories like this ever produce any new testable predictions, or is this the modern equivalent of counting angels on the head of a pin?
- eli_gottlieb 14y ago
  Funny thing: the Talmudic sages actually came to a conclusion on how many angels could dance on the head of a pin. I think it was about 16 or so.
  - Groxx 14y ago
    Well, it's obvious in retrospect, but I'd imagine that took some pretty awesome reasoning powers.
vecter 14y ago
IANAP but if universes could be born from black holes, would they also disappear if the black hole were to evaporate via Hawking radiation?
Natsu 14y ago
So what happens to those universes when Hawking radiation causes the black hole to evaporate? And if we're in a black hole, what evidence, if any, do we have for the effects of evaporation?
- JonnieCache 14y ago
  Indeed, doesn't this violate all sorts of conservation laws when you consider hawking radiation? We've spent decades trying to sort out the problems of black holes and information/entropy, surely to put a whole new universe inside every one is going to bugger it right up!
- lloeki 14y ago
  Interpreting various equations from my limited knowledge of such a discussed area, I've come up with this: Hawking radiation makes a black hole lose mass, hence diminishing its Schwarzchild radius. The Schwarzchild radius came up because it's a singularity (in the mathematical sense) in a solution to Einstein filed equations. The same way matter collapses onto itself up to creating such a singularity and being encompassed into the now existing event horizon, as soon as there is not enough mass to sustain the singularity, the event horizon vanishes, hence the remaining matter "pops" back into our sight. You could view it otherwise with a thought experiment: take particles out of the black hole one by one. Each time it will reduce the mass and maybe the radius. At some point the mass/radius ratio may not be small enough to hold light and the bubble bursts in plain sight as the event horizon breaks down. In such a thought experiment, the worst case would be that the black hole would require every single particle but one to evaporate (unless you assume a single particle could be a black hole in itself). An interesting back of the envelope calculation is computing the mass contained in a Schwartzchild radius of Planck length (the size at which quantum effects take over). l_P = sqrt(hG/c^3) r_s = 2Gm/c^2 hence m = sqrt(hc/4G) = 1.0882546265651108e-08 kg which is a bit more than 1e22 electrons sitting at a position 1e-15 smaller than a single one of them.
  - Morg 14y ago
    Black holes are just a whole lot of matter stashed in the same place, the only "strange" part is the effect of extremely intense gravity, like deviating photons to the point where you never receive them, etc. In effect the hole isn't even black it's just an effect of all light that could come from that direction being warped around it. As has been seen before with twin stars, when photons pass near very heavy objects like stars, it happens that they will have a curved trajectory, in the case of twin stars two trajectories, one left and one right of the star, causing two images of the same star. That's with a very light object compared to a blackhole. With blackholes, it simply has a curved trajectory, that orbits/crash into the black hole, thus sending absolutely no photons our way, thus no light, thus black. There is absolutely nothing mysterious about black holes, just edge effects because they're not even remotely comparable to what we can readily observe, and most closely related to the aspect of physics we understand the less : gravity. Schwarzchild radius in this case is a cool term, but it's a very simple concept, it's just the distance from the center of an object at wich photons start having non-collision trajectories (i.e. some light escapes if it has the right trajectory). http://en.wikipedia.org/wiki/Schwarzschild_radius http://en.wikipedia.org/wiki/Schwarzschild_radius Essentially. nothing particular and in fact there are event horizons inside existing matter, just that noone cares since it's inside. If you remove mass from a black hole it gets bigger, nothing new or special there, it would work the exact same way with our sun too, as when it will become a red giant, far bigger yet much lighter. If you keep removing mass from your black hole, at some point it's radius crosses it's schwarzchild radius and tadaam it's a star instead .. still the same object though. About the hawkins radiation, I have no clue, but whatever they are they seem to be considered minimal compared to the influx of mass/energy from galaxy collisions, galaxy eating and all that.
einhverfr 14y ago
I am not a physicist but I have a question about this. If matter is being sucked into a new universe from an old one, I can understand that the mass of the new universe would count on the old universe's balance sheet if you will, showing that the sum of matter and energy is still constant, but wouldn't the new universe be only partially logically self-contained in this regard? Wouldn't the sum of matter and energy be increasing? And if our universe is on the inside of a black hole, shouldn't the amount of energy and matter be increasing here as well? If not, why not? Why don't we get to suck in fading stars from our parent universe and get an increasing amount of m or e?
- chucknelson 14y ago
  I was thinking the same thing, visualizing the parent black hole still feeding on the universe "outside" of our own.
- powertower 14y ago
  I'm not sure that the extra matter ever "enters" the black hole in a traditional sense... As matter approaches it (pass the Schwarzschild radius) and increases in velocity, time slows down more and more for it. When velocity approaches C, time approaches zero. Though in another thought, I'd guess that due to the forces involved, the matter is ripped apart on a sub-quantum scale to the point that it literally disintegrates into its energy component and basically adds energy to the black hole (which can be interpreted as mass). But again, it never enters it.
  - evanb 14y ago
    This is a well-understood problem in GR. To an outside observer, things never appear to cross the Schwarzschild radius (R_S), giving the impression that time stops for in-falling matter when it gets to R_S. This, however, is an illusion forced on a distant observer. The stuff that is actually falling into the black hole never notices R_S because the velocity they measure is not greater than c, and crossing the event horizon is a completely benign event. It's the later extreme tidal forces / spaghettification that destroys in-falling matter. So it is fair to say that stuff enters a black hole.
Sander_Marechal 14y ago
What impact would this have on scenarios of the end of our universe?
SagelyGuru 14y ago
Black holes and dark matter are likely to be just artificial constructs to rescue certain mistaken orthodoxies of astro physics. Electrostatic force is much much stronger than gravity. It is known to be ubiquitous both on micro (sub-atomic) scale and on macro (cosmic) scale. Once you acknowledge its existence, it is no longer necessary to postulate black holes in the centres of galaxies to hold them together.
- Tloewald 14y ago
  Black holes have been observed (insofar as anything in astrophysics is observed) at the center of galaxies and do not suffice to explain why they hold together. So they're no longer a postulate, and they do not serve the purpose described. Dark matter and dark energy are postulated as such an explanation.
- Retric 14y ago
  I hope your kidding, but if your both serious and not trolling: Like charges repel and opposite charges attract which prevents large scale accumulation of charge in even a tiny area by cosmic scales. Gravity while locally weak does not have these issues and you can keep dumping more mass into the same area more or less indefinitely.
  - SagelyGuru 14y ago
    Dumping more and more mass into a black hole until it holds a whole universe is, apparently, not enough. But, hey, isn't it lucky that there is now also an unobservable dark matter and energy and just enough of it to make the 'gravity only' sums come out right? Hmmmm. Does this really sound more plausible to you than that widely separated bodies in vacuum, large and small, can hold charge? I hope you are kidding.
    - astrodust 14y ago
      Keep reading your high-school textbook on physics and be sure to note the equations on calculating the force of an electrostatic charge over very large distances. If you rubbed the entire galaxy with a cosmic-sized cat you still wouldn't have the effects you're postulating.
hkolek 14y ago
Ok, so if our universe is inside a black hole which is in a "parent" universe and so on, doesn't there have to be some kind of "root" universe? So where does that "root" universe come from?
- anonymoushn 14y ago
  You're very clever, young man, very clever, but it's universes all the way down!
- sigkill 14y ago
  Since there's no concept of space and time "inside" a blackhole, I think it would be better to think of blackholes as doors to different rooms in a huge mansion rather than each room having a smaller room contained inside it.
  - evanb 14y ago
    Space and time still are well defined inside of a black hole. They only break down at one point, termed the singularity. But nothing mystical happens and neither space nor time break down when you pass the event horizon. So there is indeed a well-formed notion of "inside", as long as you're not in the very center, where the singularity breaks everything.
    - sigkill 14y ago
      A black hole is technically a single point. The part of the hole that we colloquially refer to is the event horizon. The headline speaks of universes "inside" a black hole, not an event horizon. There's a brilliant explanation on reddit by RobotRollCall on this topic. I'll update my post when I find the link.
      - ithkuil 14y ago
        Perhaps you mean this thread: http://www.reddit.com/r/askscience/comments/f1lgu/what_would_happen_if_the_event_horizons_of_two/c1cuiyw http://www.reddit.com/r/askscience/comments/f1lgu/what_would...
PaulHoule 14y ago
The esact mechanism of 'Torsion' may not be right, but there have been indications for a long time that there may be another universe inside a black hole -- because if you look at the solution to Einstein's equations, there's a place on 'the other side' that is flat. If there is some process like cosmic inflation triggered by high energy densities (like Andre Linde's chaotic inflation) it's pretty believable that some kind of 'bang' happens when a black hole formss and the output of that bang fills the 'other side'.
twsted 14y ago
Sheldon Cooper, what do you think? Bazinga?
Groxx 14y ago
So, what happens when black holes collide, and merge into a single one? Serious question, btw - would we experience it, or does our universe contain all matter to ever enter our black hole, therefore all it has merged with? If the latter, how big can black holes get? Can they consume a universe? That would be a neat end-result - the whole universe goes down the drain, to cause a new one.
- kylek 14y ago
  interesting notion! who's to say the big bang wasn't caused by a supermassive blackhole on the other 'side'
  - vlisivka 14y ago
    Why you need 'other side'? Our Universe has disproportion between (visible) matter and antimatter. Black holes my contain missed anti-matter. So when black hole will consume all matter of our Universe, it will bang again, without help of any parent Universe.
    - kylek 14y ago
      I said "other 'side'", not 'other side'! (dimensions are silly :) ) However, I'm not a physicist and really have no idea what I'm talking about :( reading about cosmology is only a hobby/daydream of mine.
zellyn 14y ago
What the article doesn't mention is that the universe inside the black hole is exactly the same as this one. So if you head over to a black hole, dive in, and travel to earth, everyone welcomes you "back" and asks how it went.
- gpvos 14y ago
  I don't think that that follows in any way from the article. But the idea is interesting. Care to explain or give references?
andrethegiant 14y ago
Does this mean that black holes can be inside black holes?
- AsylumWarden 14y ago
  Black hole version of inception! http://www.imdb.com/title/tt1375666/ http://www.imdb.com/title/tt1375666/ Actually, this is much to complicated for my feeble mind. I am sticking with the "Parallel Universe Box" from the Futurama series (http://futurama.wikia.com/wiki/Parallel_Universe_Box http://futurama.wikia.com/wiki/Parallel_Universe_Box). It makes my head hurt less.
gcb 14y ago
With my highschool physics i was lost at "since energy can create matter"...
BigTuna 14y ago
On a related note, I find it very intriguing that the three properties that distinguish black holes from one another (mass, charge and spin) are the same ones that distinguish quarks. That's a beautiful symmetry between some of the smallest and largest things in existence.
k3liutZu 14y ago
So Black Holes are actually closures

203 points by robg 14y ago

cft 14y ago

In Einstein's theory of general relativity, Riemann tensor is assumed to be symmetric, due to great simplification of the theory compared to the one with non-symmetric Riemann tensor, and an absolute lack of experimental evidence to the contrary for 100 years since it was discoveried. Torsion, which is the cause of asymmetry of the Riemann tensor is set to zero. I do not know why this author is so excited about torsion tensor, the idea that torsion could be non-zero has been around for at least 90 years, but got zero traction. Disclaimer : I have a phd in string theory.

taliesinb 14y ago
I don't have a PhD in string theory, but would like to make the point that many times in the history of science ideas that were originally regarded as uninteresting lie dormant for a long time only to usefully surface much later in the context of new evidence. In this case, the researcher seems to be excited specifically because of the potential of torsion to explain dark energy -- a recently discovered phenomena (although of course, oddly presaged by Einstein's cosmological constant hack).
- cft 14y ago
  The classical theory of gravity with torsion certainly does not explain dark matter. The author is trying to build some quantum theory of gravity, where torsion is required, speculating that it would explain dark matter. I should add here that the attempts to build a quantum theory of gravity without torsion failed in the last 100 years (string theory is the best candidate), and the author is trying to add even more complexity by adding torsion tensor.
  - silentOpen 14y ago
    Complexity or model? Torsion is biplanar directed? We know quantum constants. Is a cosmological bivector so different? Should be observable? If only we could measure universal expansion accurately at small timescales, we could listen to the rain on the roof (horizon).
  - DeepDuh 14y ago
    I'm trying to follow you as a (very interested) layman, so excuse me if I'm being stupid. Couldn't the failure to build quantum gravity be BECAUSE torsion has been excluded (which is I believe what the author suggests)? Maybe this is something that has to be looked into. I'm thinking that a marriage of physics, mathematics and CS might be necessary to overcome our limits in understanding these structures. Something like an IBM Watson for physicists, where a computer is fed with all informations we have and solves an optimisation problem to come up with a unified theory explaining all the phenomenons with the least complex solution (i.e. the least universal constants). Another requirement would be to have 42 as an error code for all possible failures in the calculation ;).
  - guscost 14y ago
    Dark matter is an explanation!
  - vorg 14y ago
    The author paraphrases "spacetime tells matter how to move, and matter tells spacetime how to curve". The torsion axiom extends this to "...and matter tells spacetime how to curve and twist". The way he explains it makes it sound like an elegant way to complete the General Relativity hypothesis, which Einstein described as "the happiest thought of his life". If an axiom has a certain elegance about it, then perhaps a quantum theory of gravity without torsion is adding the complexity, not the other way around.
- jopt 14y ago
  Don't forget confirmation bias. Most dormant theories are dormant for a reason.
Steuard 14y ago
Mind you, string theory itself includes torsion: the Riemann tensor that arises in (e.g.) curved backgrounds includes contributions from the NS-NS B-field that correspond precisely to the effects of torsion. I don't think that non-zero torsion in itself is an outlandish idea, but I completely agree that it's fair to be skeptical of claims that torsion has significant observable effects. Disclaimer: I also have a PhD in string theory.
- partagas 14y ago
  >Mind you, string theory itself includes torsion I'm not sure I understand. In Riemannian geometry it might be convenient to use a connection with non-vanishing torsion, but it is not required. What do you mean by 'includes'?
  - Steuard 14y ago
    Well, to give an explicit example (sorry, non-specialists!), consider the nonlinear sigma model action for superstring theory in an arbitrary background geometry (that is, arbitrary spacetime metric G and NS-NS B-field; we'll ignore the dilaton). The coefficient of the 4-fermion term is the Riemann tensor. But if you construct that Riemann tensor just from the metric (as one does in general relativity without torsion), you'll omit essential pieces: you also need to include terms in the Riemann tensor resulting from a non-zero torsion tensor T=-dB (in differential form notation). A similar situation holds for the covariant derivatives in the fermion kinetic terms. Now, it's entirely up to you whether you write that 4-fermion term coefficient as "Riemann tensor (including torsion)" or as "Riemann tensor (torsion free) + (lots of weird, arbitrary-looking interaction terms involving derivatives of B)". So on some level, there's no reason that you must use a connection with non-vanishing torsion. But I would claim that the equations are much more elegant (and give deeper insight) when expressed with torsion "built-in". [Fun fact: So does Polchinski, but he's not talkative about it. If you look up "torsion" in the index of Vol. 2, the first reference is to the page with the equations I've referenced above... but the word "torsion" doesn't appear anywhere in the text of the page!] Aside: If anyone out there is interested in how this torsion stuff fits into the mathematics of Relativity, you might have a look at my notes on how it would be incorporated into Bob Wald's textbook: http://www.slimy.com/~steuard/teaching/tutorials/GRtorsion.pdf http://www.slimy.com/~steuard/teaching/tutorials/GRtorsion.p...

taliesinb 14y ago

Of course headlines have to be catchy, but this universe-in-a-black-hole concept is hardly a new one. Rather, the novel part here seems to be the idea that the connection in GR might might possess non-zero torsion, contrary to what is normally assumed. In the whole black-holes-create-universes vein, last century the theoretical physicist Lee Smolin presented the quite delicious idea (described in his book The Life Of the Cosmos) that entire universes might be subject to the process of natural selection. This would work if singularity formation involves the transmission of physical constants to the 'daughter' universe with slight modification, quite a thing to suppose given we don't really know what physical constants 'mean'. If it occurred, this natural selection would optimize these constants for the production of black holes, which luckily for us co-incides with the production of life-bearing stars. Of course, all very unfalsifiable, but kinda epic.

dalke 14y ago
One SF short story takes this further. The best form of interstellar travel generates black holes, so the universe is optimized for producing the type of life which does interstellar travel via that process. No need for coincidences here, and even more un-falsifiable.
- ctkrohn 14y ago
  What's the name of the short story? Sounds like it could be interesting.
  - gliese1337 14y ago
    Not sure about a short story, but there's a novel with that idea: Learning the World: a Scientific Romance by Ken MacLeod
    - pavel_lishin 14y ago
      Gregory Benford also wrote a novel that touches on this topic called "Cosm", which is a pretty excellent read.

charlieflowers 14y ago

Perhaps this helps explain Fermi's paradox (at least partly) ... some of the many, many aliens we should have found by now might be living either out in the parent universe, or inside other black holes in our universe. I'm way out on a limb here, but it's an interesting speculation. Whadda you think?

tuxcanfly 14y ago
Fermi's paradox would still hold for this universe, methinks.
- jeffool 14y ago
  Yeah, but there could be a new parenthetical, "likelihood of an alien living in another universe, multiplied by all the effects of Fermi's Paradox itself, and multiplied by the likelihood of that alien's ability to traverse universes."
  - mokus 14y ago
    I think that would be a very small extra factor, especially if you also add the likelihood of that alien's interest in traveling to specifically this part of this universe. And of course, we have no reasonable basis for estimating any of those numbers. We have a sample size of one universe and we don't even know the rate of occurrence of life in that one. Still, it can be fun to speculate.
prawn 14y ago
I don't think so because all the elements being plugged into the Drake Equation (for example) exist within our universe and not in any parental or child universes. In fact, the Drake Equation only speaks of potential life in our galaxy rather than the next step beyond that. The estimates relating to the paradox all come from what we've understood to be around us - galaxies, stars, planets, etc. (IANA anything of any consequence to this discussion - just an eager reader!)
entropy_ 14y ago
I don't think it helps much to explain Fermi's paradox since the estimation there is based on the size of the universe. If it turns out that the universe is massively bigger then so should the estimate of how many alien civilizations there are be.

ygmelnikova 14y ago

"You're very clever, young man, very clever," said the old lady. "But it's turtles all the way down!

Porter_423 14y ago

That is quite intriguing.

cwzwarich 14y ago

Will theories like this ever produce any new testable predictions, or is this the modern equivalent of counting angels on the head of a pin?

eli_gottlieb 14y ago
Funny thing: the Talmudic sages actually came to a conclusion on how many angels could dance on the head of a pin. I think it was about 16 or so.
- Groxx 14y ago
  Well, it's obvious in retrospect, but I'd imagine that took some pretty awesome reasoning powers.

vecter 14y ago

IANAP but if universes could be born from black holes, would they also disappear if the black hole were to evaporate via Hawking radiation?

Natsu 14y ago

So what happens to those universes when Hawking radiation causes the black hole to evaporate? And if we're in a black hole, what evidence, if any, do we have for the effects of evaporation?

JonnieCache 14y ago
Indeed, doesn't this violate all sorts of conservation laws when you consider hawking radiation? We've spent decades trying to sort out the problems of black holes and information/entropy, surely to put a whole new universe inside every one is going to bugger it right up!
lloeki 14y ago
Interpreting various equations from my limited knowledge of such a discussed area, I've come up with this: Hawking radiation makes a black hole lose mass, hence diminishing its Schwarzchild radius. The Schwarzchild radius came up because it's a singularity (in the mathematical sense) in a solution to Einstein filed equations. The same way matter collapses onto itself up to creating such a singularity and being encompassed into the now existing event horizon, as soon as there is not enough mass to sustain the singularity, the event horizon vanishes, hence the remaining matter "pops" back into our sight. You could view it otherwise with a thought experiment: take particles out of the black hole one by one. Each time it will reduce the mass and maybe the radius. At some point the mass/radius ratio may not be small enough to hold light and the bubble bursts in plain sight as the event horizon breaks down. In such a thought experiment, the worst case would be that the black hole would require every single particle but one to evaporate (unless you assume a single particle could be a black hole in itself). An interesting back of the envelope calculation is computing the mass contained in a Schwartzchild radius of Planck length (the size at which quantum effects take over). l_P = sqrt(hG/c^3) r_s = 2Gm/c^2 hence m = sqrt(hc/4G) = 1.0882546265651108e-08 kg which is a bit more than 1e22 electrons sitting at a position 1e-15 smaller than a single one of them.
- Morg 14y ago
  Black holes are just a whole lot of matter stashed in the same place, the only "strange" part is the effect of extremely intense gravity, like deviating photons to the point where you never receive them, etc. In effect the hole isn't even black it's just an effect of all light that could come from that direction being warped around it. As has been seen before with twin stars, when photons pass near very heavy objects like stars, it happens that they will have a curved trajectory, in the case of twin stars two trajectories, one left and one right of the star, causing two images of the same star. That's with a very light object compared to a blackhole. With blackholes, it simply has a curved trajectory, that orbits/crash into the black hole, thus sending absolutely no photons our way, thus no light, thus black. There is absolutely nothing mysterious about black holes, just edge effects because they're not even remotely comparable to what we can readily observe, and most closely related to the aspect of physics we understand the less : gravity. Schwarzchild radius in this case is a cool term, but it's a very simple concept, it's just the distance from the center of an object at wich photons start having non-collision trajectories (i.e. some light escapes if it has the right trajectory). http://en.wikipedia.org/wiki/Schwarzschild_radius http://en.wikipedia.org/wiki/Schwarzschild_radius Essentially. nothing particular and in fact there are event horizons inside existing matter, just that noone cares since it's inside. If you remove mass from a black hole it gets bigger, nothing new or special there, it would work the exact same way with our sun too, as when it will become a red giant, far bigger yet much lighter. If you keep removing mass from your black hole, at some point it's radius crosses it's schwarzchild radius and tadaam it's a star instead .. still the same object though. About the hawkins radiation, I have no clue, but whatever they are they seem to be considered minimal compared to the influx of mass/energy from galaxy collisions, galaxy eating and all that.

einhverfr 14y ago

I am not a physicist but I have a question about this. If matter is being sucked into a new universe from an old one, I can understand that the mass of the new universe would count on the old universe's balance sheet if you will, showing that the sum of matter and energy is still constant, but wouldn't the new universe be only partially logically self-contained in this regard? Wouldn't the sum of matter and energy be increasing? And if our universe is on the inside of a black hole, shouldn't the amount of energy and matter be increasing here as well? If not, why not? Why don't we get to suck in fading stars from our parent universe and get an increasing amount of m or e?

chucknelson 14y ago
I was thinking the same thing, visualizing the parent black hole still feeding on the universe "outside" of our own.
powertower 14y ago
I'm not sure that the extra matter ever "enters" the black hole in a traditional sense... As matter approaches it (pass the Schwarzschild radius) and increases in velocity, time slows down more and more for it. When velocity approaches C, time approaches zero. Though in another thought, I'd guess that due to the forces involved, the matter is ripped apart on a sub-quantum scale to the point that it literally disintegrates into its energy component and basically adds energy to the black hole (which can be interpreted as mass). But again, it never enters it.
- evanb 14y ago
  This is a well-understood problem in GR. To an outside observer, things never appear to cross the Schwarzschild radius (R_S), giving the impression that time stops for in-falling matter when it gets to R_S. This, however, is an illusion forced on a distant observer. The stuff that is actually falling into the black hole never notices R_S because the velocity they measure is not greater than c, and crossing the event horizon is a completely benign event. It's the later extreme tidal forces / spaghettification that destroys in-falling matter. So it is fair to say that stuff enters a black hole.

Sander_Marechal 14y ago

What impact would this have on scenarios of the end of our universe?

SagelyGuru 14y ago

Black holes and dark matter are likely to be just artificial constructs to rescue certain mistaken orthodoxies of astro physics. Electrostatic force is much much stronger than gravity. It is known to be ubiquitous both on micro (sub-atomic) scale and on macro (cosmic) scale. Once you acknowledge its existence, it is no longer necessary to postulate black holes in the centres of galaxies to hold them together.

Tloewald 14y ago
Black holes have been observed (insofar as anything in astrophysics is observed) at the center of galaxies and do not suffice to explain why they hold together. So they're no longer a postulate, and they do not serve the purpose described. Dark matter and dark energy are postulated as such an explanation.
Retric 14y ago
I hope your kidding, but if your both serious and not trolling: Like charges repel and opposite charges attract which prevents large scale accumulation of charge in even a tiny area by cosmic scales. Gravity while locally weak does not have these issues and you can keep dumping more mass into the same area more or less indefinitely.
- SagelyGuru 14y ago
  Dumping more and more mass into a black hole until it holds a whole universe is, apparently, not enough. But, hey, isn't it lucky that there is now also an unobservable dark matter and energy and just enough of it to make the 'gravity only' sums come out right? Hmmmm. Does this really sound more plausible to you than that widely separated bodies in vacuum, large and small, can hold charge? I hope you are kidding.
  - astrodust 14y ago
    Keep reading your high-school textbook on physics and be sure to note the equations on calculating the force of an electrostatic charge over very large distances. If you rubbed the entire galaxy with a cosmic-sized cat you still wouldn't have the effects you're postulating.

hkolek 14y ago

Ok, so if our universe is inside a black hole which is in a "parent" universe and so on, doesn't there have to be some kind of "root" universe? So where does that "root" universe come from?

anonymoushn 14y ago
You're very clever, young man, very clever, but it's universes all the way down!
sigkill 14y ago
Since there's no concept of space and time "inside" a blackhole, I think it would be better to think of blackholes as doors to different rooms in a huge mansion rather than each room having a smaller room contained inside it.
- evanb 14y ago
  Space and time still are well defined inside of a black hole. They only break down at one point, termed the singularity. But nothing mystical happens and neither space nor time break down when you pass the event horizon. So there is indeed a well-formed notion of "inside", as long as you're not in the very center, where the singularity breaks everything.
  - sigkill 14y ago
    A black hole is technically a single point. The part of the hole that we colloquially refer to is the event horizon. The headline speaks of universes "inside" a black hole, not an event horizon. There's a brilliant explanation on reddit by RobotRollCall on this topic. I'll update my post when I find the link.
    - ithkuil 14y ago
      Perhaps you mean this thread: http://www.reddit.com/r/askscience/comments/f1lgu/what_would_happen_if_the_event_horizons_of_two/c1cuiyw http://www.reddit.com/r/askscience/comments/f1lgu/what_would...

PaulHoule 14y ago

The esact mechanism of 'Torsion' may not be right, but there have been indications for a long time that there may be another universe inside a black hole -- because if you look at the solution to Einstein's equations, there's a place on 'the other side' that is flat. If there is some process like cosmic inflation triggered by high energy densities (like Andre Linde's chaotic inflation) it's pretty believable that some kind of 'bang' happens when a black hole formss and the output of that bang fills the 'other side'.

twsted 14y ago

Sheldon Cooper, what do you think? Bazinga?

Groxx 14y ago

So, what happens when black holes collide, and merge into a single one? Serious question, btw - would we experience it, or does our universe contain all matter to ever enter our black hole, therefore all it has merged with? If the latter, how big can black holes get? Can they consume a universe? That would be a neat end-result - the whole universe goes down the drain, to cause a new one.

kylek 14y ago
interesting notion! who's to say the big bang wasn't caused by a supermassive blackhole on the other 'side'
- vlisivka 14y ago
  Why you need 'other side'? Our Universe has disproportion between (visible) matter and antimatter. Black holes my contain missed anti-matter. So when black hole will consume all matter of our Universe, it will bang again, without help of any parent Universe.
  - kylek 14y ago
    I said "other 'side'", not 'other side'! (dimensions are silly :) ) However, I'm not a physicist and really have no idea what I'm talking about :( reading about cosmology is only a hobby/daydream of mine.

zellyn 14y ago

What the article doesn't mention is that the universe inside the black hole is exactly the same as this one. So if you head over to a black hole, dive in, and travel to earth, everyone welcomes you "back" and asks how it went.

gpvos 14y ago
I don't think that that follows in any way from the article. But the idea is interesting. Care to explain or give references?

andrethegiant 14y ago

Does this mean that black holes can be inside black holes?

AsylumWarden 14y ago
Black hole version of inception! http://www.imdb.com/title/tt1375666/ http://www.imdb.com/title/tt1375666/ Actually, this is much to complicated for my feeble mind. I am sticking with the "Parallel Universe Box" from the Futurama series (http://futurama.wikia.com/wiki/Parallel_Universe_Box http://futurama.wikia.com/wiki/Parallel_Universe_Box). It makes my head hurt less.

gcb 14y ago

With my highschool physics i was lost at "since energy can create matter"...

BigTuna 14y ago

On a related note, I find it very intriguing that the three properties that distinguish black holes from one another (mass, charge and spin) are the same ones that distinguish quarks. That's a beautiful symmetry between some of the smallest and largest things in existence.

k3liutZu 14y ago

So Black Holes are actually closures