14 ms·

Astrophysicists propose new twist on Big Bang

84 points by blazar 12y ago

trhway 12y ago
>The researchers emphasize that this idea, though it may sound absurd, is grounded firmly in the mathematics describing space and time. Specifically they’ve used the tools of holography to “turn the big bang into a cosmic mirage.” embedding into higher dimension spaces (or in general - into more "richer" structures) is a convenient mathematical tool and it works nice ... in mathematics. To work in physics that higher dimension space must really exist. Otherwsie, for all we know, out Universe can be just a 3d surface of a 4d nut that a small 4d squirrel puppy is about to bite into.
- Zarathust 12y ago
  The next phrase mentions that this theory is testable >Along the way, their model appears to address long-standing cosmological puzzles, and – crucially – produce testable predictions. I'm very curious to know how.
  - adinb 12y ago
    From the fine paper[1]: Finally, let us comment on potential testability of this model. As we pointed out, the simple model of cosmological perturbations, developed in Sec. 4 is already ruled out by cosmo- logical observations at > 5σ level, as it does not predict any deviations from scale-invariance. However, it is easy to imagine small corrections that could lead to a ∼ 4% deviation from scale-invariance, especially given that bulk temperature is so close (i.e. ∼ 20% of) the 5D Planck temperature. In the context of our model, the red tilt of the cosmological power spectrum implies that the amplitude of 5D bulk graviton propagator, which enters in Eq. (4.8), is getting stronger in the IR, suggesting gradual unfreezing of additional polarizations of graviton. [1]:http://arxiv.org/pdf/1309.1487v2 http://arxiv.org/pdf/1309.1487v2
    - sp332 12y ago
      So, if we look at parts of space further away from us (so the light reaching us tells us about older times), we should see fewer kinds of gravitons than we see around us now?
    - dhimes 12y ago
      So all we have to do is detect, over time, more polarization states of the 5-D graviton. Seems simple enough.
    - Zarathust 12y ago
      I'm not sure of what a graviton is, but wikipedia tells me that it is not detectable by any current mean. I'd be tempted to say in light of this that their theory is not testable either. http://en.wikipedia.org/wiki/Graviton http://en.wikipedia.org/wiki/Graviton
      - fragmede 12y ago
        > any current mean[s] But that's the point, innit. Who's to say we don't discover magic quantum carbon nanotubes or something thing that makes it feasible to setup a graviton detector at some point in the future. And who's to say it won't be useful, either. I'm serious; the Higgs-Boson was theorized to exist in 1964, and was proven to exist only after great expense in 2012, utilizing many cutting edge technologies. General Relativity was theorized in 1915, but not really tested in 1959, and now I use it almost every day in the form of GPS.
        dhimes 12y ago
        At the point it we can test it, it becomes testable. The authors, note, did not claim it was testable. They simply indicated the direction research should go in order to test it. As per Einstein, it's true that accurate measurements of his GR effects didn't come along for decades, but he was answering known physical problems. And the crude measurements of his day aligned with his predictions, they just weren't accurate yet.
      - Mikechaos 12y ago
- collyw 12y ago
  Ignorant question here, but is it not the case that the normal laws of physics don't apply at big bang time? Do we expect the laws of mathematics to still apply? Does anyone really have any clue about this stuff?
  - yincrash 12y ago
    #BigBangAgnostic
  - pawn 12y ago
    It's always been my understanding that the normal laws of physics don't work at big bang time as well. One thing I've wondered about is how people are so adamantly confident in the theory of the Big Bang in light of this. Is it simply because they don't like the alternatives, because they've never been heard an alternative, or is there a better reason?
    - collyw 12y ago
      It's basically a belief system at that stage. It doesn't provide any more believable answers than religion for me.
      - nitrogen 12y ago
        The big bang, unlike theology, tells us why distant objects are more red than close objects, why we can't see anything further than ~13bil light years away, why there is microwave noise everywhere, etc. The mathematics that describe all those things imply certain things about earlier cosmological history.
        collyw 12y ago
        But still doesn't prove anything about where the universe "came from".
        BgSpnnrs 12y ago
- noobermin 12y ago
  You apparently were flagged by a theoretical physicist. A lot of "physicists" nowadays forget that we're supposed to be scientists, not dreamers. Dreams are nice, but experiment and observations valid theory. I agree. Unless this has some modifications to the current model of the big bang which leads to _observable_effects_ , I don't know if this theory could even be validated as...well theory.
  - Iftheshoefits 12y ago
    There are still theoretical physicists who rely on empirical validation of the hypotheses we create. That's rather the whole point, and I'd venture (hope?) that only a small fraction of theoretical physicist think otherwise.
  - jafaku 12y ago
    You know theory means explanation, not imagination, right?
    - noobermin 12y ago
      I use the definition for theory as a hypothesis that has received sufficient experimental validation. So, by definition, many of the frontier quantum-gravity stuff doesn't fit this, unfortunately as compelling and fascinating as they are. Again, I'm just agreeing with what s/he said, that unless we have experiment/observation, we don't know whether this really describes our universe's origins and/or evolution.
- AnimalMuppet 12y ago
  Well... things that are mathematically equivalent turn out to have physical implications more often than one would expect. Not always, but often enough to be worth a look. Does the mathematical equivalence mean anything more than "maybe somebody ought to look at that a bit more"? No, but that's still more than nothing.
- coldtea 12y ago
  >embedding into higher dimension spaces (or in general - into more "richer" structures) is a convenient mathematical tool and it works nice ... in mathematics. To work in physics that higher dimension space must really exist. I'd put my money on those Phds in physics knowing that already. They probably heard about Occam too. Building a model based on specific reading on the current knowledge of physics, intuitions that hold true in light of this knowledge, and some mathematical tools, is a valid process, despite not being immediately empirically checkable. The "exists" part can be tested later. That doesn't make their work equal to abitrary BS like "a 4d nut that a small 4d squirrel puppy is about to bite into".
- BgSpnnrs 12y ago
  >Otherwsie, for all we know, out Universe can be just a 3d surface of a 4d nut that a small 4d squirrel puppy is about to bite into. absolutely. I know you are trying to portray such a scenario as incredulous, but it's entirely feasible.
adinb 12y ago
Original paper title: Out of the White Hole: A Holographic Origin for the Big Bang Arxive page (w/abstract): http://arxiv.org/abs/1309.1487 http://arxiv.org/abs/1309.1487 Direct link to paper: http://arxiv.org/pdf/1309.1487v2 http://arxiv.org/pdf/1309.1487v2
joe_the_user 12y ago
OK, The thing about this popular article is it seems to imply that the universe coming out of a black hole is different from it coming out from any kind of singularity. Well, reading the real article, it seems this popular article got things garbled. The main problem they seem raise with the big bang is that it is a "naked" singularity - there's no barrier between the world and the singular point. So what they are doing is looking at a higher dimensional black hole and finding a non-naked singularity that would generate approximately the same effects as the big bang. There is still a singularity at work here, it is simply that the singularity is not directly spewing matter out. "No naked singularities" is a general principle I recall from scanning general relativity articles.
biot 12y ago
This isn't a particularly new twist. The idea of our universe coming from a black hole has been around for quite some time, as this 1998 article discusses: http://martinelli.org/rexpansion/bhole.htm http://martinelli.org/rexpansion/bhole.htm "if we run time forwards, we can kind of visualize the beginning of our universe as a very rapid collapse (the inverse of "Inflation"). A similar kind of event happens when a star (hot, spherical, massive, dense...) becomes so dense and massive it collapses in on itself and forms that mysterious black hole. Here's an interesting question to explore... "Did our universe begin as a star that underwent a gravitational collapse?" I.e., do we live in a black hole?" Perhaps the novelty is a formal theory around the idea?
thisjepisje 12y ago
So how did this 4d universe come about? :D
GorgeRonde 12y ago
This tends to confirm Lee Smolin's embryo-theory of cosmological natural selection. Source : http://en.m.wikipedia.org/wiki/Cosmological_natural_selection#Cosmological_natural_selection http://en.m.wikipedia.org/wiki/Cosmological_natural_selectio... Cosmological natural selection Smolin's hypothesis of cosmological natural selection, also called the fecund universes theory, suggests that a process analogous to biological natural selection applies at the grandest of scales. Smolin published the idea in 1992 and summarized it in a book aimed at a lay audience called The Life of the Cosmos. The theory surmises that a collapsing[clarification needed] black hole causes the emergence of a new universe on the "other side", whose fundamental constant parameters (masses of elementary particles, Planck constant, elementary charge, and so forth) may differ slightly from those of the universe where the black hole collapsed. Each universe thus gives rise to as many new universes as it has black holes. The theory contains the evolutionary ideas of "reproduction" and "mutation" of universes, and so is formally analogous to models of population biology. The resulting population of universes can be represented as a distribution of a landscape of parameters where the height of the landscape is proportional to the numbers of black holes that a universe with those parameters will have. Applying reasoning borrowed from the study of fitness landscapes in population biology, one can conclude that the population is dominated by universes whose parameters drive the production of black holes to a local peak in the landscape. This was the first use of the notion of a landscape of parameters in physics. Leonard Susskind, who later promoted a similar string theory landscape, stated: "I'm not sure why Smolin's idea didn't attract much attention. I actually think it deserved far more than it got."
- gizmo686 12y ago
  It seems like the proposed cosmological natural selection is fundamentally different from biological natural selection in the sense that there is no actual pruning. That is to say that given a universe all of its children will survive and reproduce based solely on their laws of physics, independent of what all the other universes do. This would mean that all possible universes which could be reached through this mechanism will be reached, wheras in evolution as it happens on Earth, most of the potential organisms never exist because there ancestor got out-competed at some point.
calhoun137 12y ago
I think this idea is almost certainly false, and it has it's genesis from a mostly discredited psuedo-physics theory called the holographic universe[1]. But at least there is a testable prediction! In my opinion, the fact that they offer a testable prediction merits a more thorough consideration of the claims. First of all, it has been well understood for multiple decades that the General Relativity(GR) breaks down, and is no longer true, at mass/energy scales that are present inside of a black hole. This is known because physical quantities must be finite, but GR predicts the strength of a gravitational field inside of a black hole is infinite. If string theory is true (and I don't believe it is), then this would be a valid situation to apply it to, since we know that there is unknown physics at play inside of a black hole. Furthermore, the standard big bang cosmology is based on the idea that the beginning of time is a "black hole in time", in the sense that as t->0, the strength of the gravitational field diverges to infinity. Thus, it has been well known for decades that GR is not a valid physical theory at very short time scales after the beginning of time (this would be the epoch of inflation[3]). It is perhaps not apparent to the casual observer that this paper is based on a very bizarre sect within string theory, known as the "Holographic Universe", which according to Wikipedia "suggests that the entire universe can be seen as a two-dimensional information structure "painted" on the cosmological horizon". This is just a bunch of fancy words designed to blow smoke in your eyes, and the entire theory is sort of a joke as far as most physicists I know are concerned. There are actually a number of strange cults within string theory, another one that is good for a laugh is the Anthropic Princple[4]. This theory claims that even though the 11 dimensional D-Brane that is folded into a Calubi-Yau manifold upon which string theory is based predicts trillions of possible universes, the universe we live in exists because it is the only possible one we could live in: "the conditions happen to be just right for the existence of (intelligent) life on the earth at the present time. For if they were not just right, then we should not have found ourselves to be here now, but somewhere else, at some other appropriate time." This kind of nonsense is why I left research in theoretical physics to purse computer science and programming, which truly is the cutting edge of science. There is a lot of valuable physics research going on in material science departments(for example), but the string theory department needs to constantly justify their funding by making extremely bold claims such as "what we perceive as the Big Bang could be the three-dimensional “mirage” of a collapsing star in a universe profoundly different than our own". [1] http://en.wikipedia.org/wiki/Holographic_principle http://en.wikipedia.org/wiki/Holographic_principle [2] http://en.wikipedia.org/wiki/D-brane http://en.wikipedia.org/wiki/D-brane [3] http://en.wikipedia.org/wiki/Inflation_(cosmology) http://en.wikipedia.org/wiki/Inflation_(cosmology) [4] http://en.wikipedia.org/wiki/Anthropic_principle http://en.wikipedia.org/wiki/Anthropic_principle

84 points by blazar 12y ago

>The researchers emphasize that this idea, though it may sound absurd, is grounded firmly in the mathematics describing space and time. Specifically they’ve used the tools of holography to “turn the big bang into a cosmic mirage.” embedding into higher dimension spaces (or in general - into more "richer" structures) is a convenient mathematical tool and it works nice ... in mathematics. To work in physics that higher dimension space must really exist. Otherwsie, for all we know, out Universe can be just a 3d surface of a 4d nut that a small 4d squirrel puppy is about to bite into.

Zarathust 12y ago
The next phrase mentions that this theory is testable >Along the way, their model appears to address long-standing cosmological puzzles, and – crucially – produce testable predictions. I'm very curious to know how.
- adinb 12y ago
  From the fine paper[1]: Finally, let us comment on potential testability of this model. As we pointed out, the simple model of cosmological perturbations, developed in Sec. 4 is already ruled out by cosmo- logical observations at > 5σ level, as it does not predict any deviations from scale-invariance. However, it is easy to imagine small corrections that could lead to a ∼ 4% deviation from scale-invariance, especially given that bulk temperature is so close (i.e. ∼ 20% of) the 5D Planck temperature. In the context of our model, the red tilt of the cosmological power spectrum implies that the amplitude of 5D bulk graviton propagator, which enters in Eq. (4.8), is getting stronger in the IR, suggesting gradual unfreezing of additional polarizations of graviton. [1]:http://arxiv.org/pdf/1309.1487v2 http://arxiv.org/pdf/1309.1487v2
  - sp332 12y ago
    So, if we look at parts of space further away from us (so the light reaching us tells us about older times), we should see fewer kinds of gravitons than we see around us now?
  - dhimes 12y ago
    So all we have to do is detect, over time, more polarization states of the 5-D graviton. Seems simple enough.
  - Zarathust 12y ago
    I'm not sure of what a graviton is, but wikipedia tells me that it is not detectable by any current mean. I'd be tempted to say in light of this that their theory is not testable either. http://en.wikipedia.org/wiki/Graviton http://en.wikipedia.org/wiki/Graviton
    - fragmede 12y ago
      > any current mean[s] But that's the point, innit. Who's to say we don't discover magic quantum carbon nanotubes or something thing that makes it feasible to setup a graviton detector at some point in the future. And who's to say it won't be useful, either. I'm serious; the Higgs-Boson was theorized to exist in 1964, and was proven to exist only after great expense in 2012, utilizing many cutting edge technologies. General Relativity was theorized in 1915, but not really tested in 1959, and now I use it almost every day in the form of GPS.
      - dhimes 12y ago
        At the point it we can test it, it becomes testable. The authors, note, did not claim it was testable. They simply indicated the direction research should go in order to test it. As per Einstein, it's true that accurate measurements of his GR effects didn't come along for decades, but he was answering known physical problems. And the crude measurements of his day aligned with his predictions, they just weren't accurate yet.
    - Mikechaos 12y ago
collyw 12y ago
Ignorant question here, but is it not the case that the normal laws of physics don't apply at big bang time? Do we expect the laws of mathematics to still apply? Does anyone really have any clue about this stuff?
- yincrash 12y ago
  #BigBangAgnostic
- pawn 12y ago
  It's always been my understanding that the normal laws of physics don't work at big bang time as well. One thing I've wondered about is how people are so adamantly confident in the theory of the Big Bang in light of this. Is it simply because they don't like the alternatives, because they've never been heard an alternative, or is there a better reason?
  - collyw 12y ago
    It's basically a belief system at that stage. It doesn't provide any more believable answers than religion for me.
    - nitrogen 12y ago
      The big bang, unlike theology, tells us why distant objects are more red than close objects, why we can't see anything further than ~13bil light years away, why there is microwave noise everywhere, etc. The mathematics that describe all those things imply certain things about earlier cosmological history.
      - collyw 12y ago
        But still doesn't prove anything about where the universe "came from".
        BgSpnnrs 12y ago
noobermin 12y ago
You apparently were flagged by a theoretical physicist. A lot of "physicists" nowadays forget that we're supposed to be scientists, not dreamers. Dreams are nice, but experiment and observations valid theory. I agree. Unless this has some modifications to the current model of the big bang which leads to _observable_effects_ , I don't know if this theory could even be validated as...well theory.
- Iftheshoefits 12y ago
  There are still theoretical physicists who rely on empirical validation of the hypotheses we create. That's rather the whole point, and I'd venture (hope?) that only a small fraction of theoretical physicist think otherwise.
- jafaku 12y ago
  You know theory means explanation, not imagination, right?
  - noobermin 12y ago
    I use the definition for theory as a hypothesis that has received sufficient experimental validation. So, by definition, many of the frontier quantum-gravity stuff doesn't fit this, unfortunately as compelling and fascinating as they are. Again, I'm just agreeing with what s/he said, that unless we have experiment/observation, we don't know whether this really describes our universe's origins and/or evolution.
AnimalMuppet 12y ago
Well... things that are mathematically equivalent turn out to have physical implications more often than one would expect. Not always, but often enough to be worth a look. Does the mathematical equivalence mean anything more than "maybe somebody ought to look at that a bit more"? No, but that's still more than nothing.
coldtea 12y ago
>embedding into higher dimension spaces (or in general - into more "richer" structures) is a convenient mathematical tool and it works nice ... in mathematics. To work in physics that higher dimension space must really exist. I'd put my money on those Phds in physics knowing that already. They probably heard about Occam too. Building a model based on specific reading on the current knowledge of physics, intuitions that hold true in light of this knowledge, and some mathematical tools, is a valid process, despite not being immediately empirically checkable. The "exists" part can be tested later. That doesn't make their work equal to abitrary BS like "a 4d nut that a small 4d squirrel puppy is about to bite into".
BgSpnnrs 12y ago
>Otherwsie, for all we know, out Universe can be just a 3d surface of a 4d nut that a small 4d squirrel puppy is about to bite into. absolutely. I know you are trying to portray such a scenario as incredulous, but it's entirely feasible.

adinb 12y ago

Original paper title: Out of the White Hole: A Holographic Origin for the Big Bang Arxive page (w/abstract): http://arxiv.org/abs/1309.1487 http://arxiv.org/abs/1309.1487 Direct link to paper: http://arxiv.org/pdf/1309.1487v2 http://arxiv.org/pdf/1309.1487v2

joe_the_user 12y ago

OK, The thing about this popular article is it seems to imply that the universe coming out of a black hole is different from it coming out from any kind of singularity. Well, reading the real article, it seems this popular article got things garbled. The main problem they seem raise with the big bang is that it is a "naked" singularity - there's no barrier between the world and the singular point. So what they are doing is looking at a higher dimensional black hole and finding a non-naked singularity that would generate approximately the same effects as the big bang. There is still a singularity at work here, it is simply that the singularity is not directly spewing matter out. "No naked singularities" is a general principle I recall from scanning general relativity articles.

biot 12y ago

This isn't a particularly new twist. The idea of our universe coming from a black hole has been around for quite some time, as this 1998 article discusses: http://martinelli.org/rexpansion/bhole.htm http://martinelli.org/rexpansion/bhole.htm "if we run time forwards, we can kind of visualize the beginning of our universe as a very rapid collapse (the inverse of "Inflation"). A similar kind of event happens when a star (hot, spherical, massive, dense...) becomes so dense and massive it collapses in on itself and forms that mysterious black hole. Here's an interesting question to explore... "Did our universe begin as a star that underwent a gravitational collapse?" I.e., do we live in a black hole?" Perhaps the novelty is a formal theory around the idea?

thisjepisje 12y ago

So how did this 4d universe come about? :D

GorgeRonde 12y ago

This tends to confirm Lee Smolin's embryo-theory of cosmological natural selection. Source : http://en.m.wikipedia.org/wiki/Cosmological_natural_selection#Cosmological_natural_selection http://en.m.wikipedia.org/wiki/Cosmological_natural_selectio... Cosmological natural selection Smolin's hypothesis of cosmological natural selection, also called the fecund universes theory, suggests that a process analogous to biological natural selection applies at the grandest of scales. Smolin published the idea in 1992 and summarized it in a book aimed at a lay audience called The Life of the Cosmos. The theory surmises that a collapsing[clarification needed] black hole causes the emergence of a new universe on the "other side", whose fundamental constant parameters (masses of elementary particles, Planck constant, elementary charge, and so forth) may differ slightly from those of the universe where the black hole collapsed. Each universe thus gives rise to as many new universes as it has black holes. The theory contains the evolutionary ideas of "reproduction" and "mutation" of universes, and so is formally analogous to models of population biology. The resulting population of universes can be represented as a distribution of a landscape of parameters where the height of the landscape is proportional to the numbers of black holes that a universe with those parameters will have. Applying reasoning borrowed from the study of fitness landscapes in population biology, one can conclude that the population is dominated by universes whose parameters drive the production of black holes to a local peak in the landscape. This was the first use of the notion of a landscape of parameters in physics. Leonard Susskind, who later promoted a similar string theory landscape, stated: "I'm not sure why Smolin's idea didn't attract much attention. I actually think it deserved far more than it got."

gizmo686 12y ago
It seems like the proposed cosmological natural selection is fundamentally different from biological natural selection in the sense that there is no actual pruning. That is to say that given a universe all of its children will survive and reproduce based solely on their laws of physics, independent of what all the other universes do. This would mean that all possible universes which could be reached through this mechanism will be reached, wheras in evolution as it happens on Earth, most of the potential organisms never exist because there ancestor got out-competed at some point.

calhoun137 12y ago

I think this idea is almost certainly false, and it has it's genesis from a mostly discredited psuedo-physics theory called the holographic universe[1]. But at least there is a testable prediction! In my opinion, the fact that they offer a testable prediction merits a more thorough consideration of the claims. First of all, it has been well understood for multiple decades that the General Relativity(GR) breaks down, and is no longer true, at mass/energy scales that are present inside of a black hole. This is known because physical quantities must be finite, but GR predicts the strength of a gravitational field inside of a black hole is infinite. If string theory is true (and I don't believe it is), then this would be a valid situation to apply it to, since we know that there is unknown physics at play inside of a black hole. Furthermore, the standard big bang cosmology is based on the idea that the beginning of time is a "black hole in time", in the sense that as t->0, the strength of the gravitational field diverges to infinity. Thus, it has been well known for decades that GR is not a valid physical theory at very short time scales after the beginning of time (this would be the epoch of inflation[3]). It is perhaps not apparent to the casual observer that this paper is based on a very bizarre sect within string theory, known as the "Holographic Universe", which according to Wikipedia "suggests that the entire universe can be seen as a two-dimensional information structure "painted" on the cosmological horizon". This is just a bunch of fancy words designed to blow smoke in your eyes, and the entire theory is sort of a joke as far as most physicists I know are concerned. There are actually a number of strange cults within string theory, another one that is good for a laugh is the Anthropic Princple[4]. This theory claims that even though the 11 dimensional D-Brane that is folded into a Calubi-Yau manifold upon which string theory is based predicts trillions of possible universes, the universe we live in exists because it is the only possible one we could live in: "the conditions happen to be just right for the existence of (intelligent) life on the earth at the present time. For if they were not just right, then we should not have found ourselves to be here now, but somewhere else, at some other appropriate time." This kind of nonsense is why I left research in theoretical physics to purse computer science and programming, which truly is the cutting edge of science. There is a lot of valuable physics research going on in material science departments(for example), but the string theory department needs to constantly justify their funding by making extremely bold claims such as "what we perceive as the Big Bang could be the three-dimensional “mirage” of a collapsing star in a universe profoundly different than our own". [1] http://en.wikipedia.org/wiki/Holographic_principle http://en.wikipedia.org/wiki/Holographic_principle [2] http://en.wikipedia.org/wiki/D-brane http://en.wikipedia.org/wiki/D-brane [3] http://en.wikipedia.org/wiki/Inflation_(cosmology) http://en.wikipedia.org/wiki/Inflation_(cosmology) [4] http://en.wikipedia.org/wiki/Anthropic_principle http://en.wikipedia.org/wiki/Anthropic_principle