7 ms·

When are we gonna find a WHITE HOLE as predicted in Veritasium's video? https://www.youtube.com/watch?v=6akmv1bsz1M https://www.youtube.com/watch?v=6akmv1bsz1M

ndsipa_pomu 2y ago
Are you sure that the big bang wasn't one?
- raattgift 2y ago
  Yes, we can be certain. White holes can be considered in two ways: (1) a region of spacetime into which nothing can ever cross, with a surface that is a perfect reflector; or somewhat less commonly (2) a time-reversed black hole. At scales of gigaparsecs, the universe appears to be both spatially homogeneous and isotropic, with matter denser at higher redshift. There is no way to generate this configuration of matter from a white hole. White holes are very much spatially anisotropic, that is you can point to where they are: left of you but not right of you, in front of you but not behind you, etc. The trajectories of the centres of momentum of galaxy clusters in every direction and at every redshift are diverging but not following an inertial radial. The really compelling accessible evidence against a white hole big bang is in the https://en.wikipedia.org/wiki/Lyman-alpha_forest https://en.wikipedia.org/wiki/Lyman-alpha_forest from hydrogen clouds at different redshifts being backlit by bright background (and thus earlier in the universe) sources. This "stacking" is so hard to conceive for a white hole big bang that as far as I know, nobody has actually written down a reasonable explanation for it. More technically, (general relativity) metrics at those "cosmologically large" scales are so different from the metrics of white holes that we would already have noticed. Additionally, a white hole big bang has to account for the chemistry of the earliest visible stars, whose spectral lines indicate essentially hydrogen with a tiny amount of helium and lithium. The standard cosmology's big bang nucleosynthesis's chemical abundances would have to be duplicated by a white hole big bang, and as far as I know nobody knows how to make that work. How does whatever is spit out of a white hole interior, or reflected off a white hole boundary, eventually turn into atomic hydrogen (with a smattering of heavier atoms up to 7 atomic mass units)? How does it account for the cosmic microwave background, which implies that in some region of the white hole big bang universe atoms practically everywhere were so hot as to be completely ionized? Likewise, the interior metrics of black holes are very different from metrics which reasonably describe observations at gigaparsec scales. So if one takes a "wormhole" maximal extension of a black hole spacetime and throws enormous amounts matter into the black hole end, what emerges at the white hole end is nothing like a cosmology. Nor is what's inside. So a reasonable prediction of our galaxy's future is not exiting from a white hole (with us presently inside), and a reasonable prediction of our past is not that our galaxy was spit out of a white hole (with us presently outside). As far as I know, nobody has done a convincing treatment of a non-eternal white hole in General Relativity. We've had theoretical models for forming black holes (i.e., there is a past of the black hole where there is no black hole yet, so it's non-eternal) since the 1930s (<https://en.wikipedia.org/wiki/Oppenheimer%E2%80%93Snyder_model https://en.wikipedia.org/wiki/Oppenheimer%E2%80%93Snyder_mod...>), and models for evaporating black holes since Hawking 1970, so it's quite striking there's nothing similar for white holes. There is ample astrophysical evidence supporting a range of models for non-eternal black holes and their horizons. There isn't anything seen by our telescopes that looks like it might be a white hole horizon. The accelerated expansion of the universe, discovered in 1998, kills off a bunch of vaguely related ideas, like we are in a tiny tiny fraction of a thin shell (thin as in small compared to the shell's diameter) of matter that is expanding inertially from an initial impulse (an "explosion", figuratively) acting on a dense phase of matter. By "tiny tiny" here we're talking about our visible universe occupying less than 10^-23 of the shell's thickness. This is from a family of ideas tossed around a bit before Alan Guth published his 1997 book <https://en.wikipedia.org/wiki/The_Inflationary_Universe https://en.wikipedia.org/wiki/The_Inflationary_Universe>. One could imagine a reflector onto which the shell fell, and that reflector could resemble a white hole; you can get a cyclic cosmology by having the entire shell eventually reconverge on the central reflector. However, we now see the expansion of our universe is speeding up rather than slowing down, so this doesn't work. Finally, we're learning a lot more about the gravitational wave background of our universe. It is reasonable to bet that studies of the polarization of the cosmic microwave background (e.g. <https://lweb.cfa.harvard.edu/~cbischoff/bicepkeck/ https://lweb.cfa.harvard.edu/~cbischoff/bicepkeck/>) will find evidence of gravitational waves at scales large enough and uniform enough to rule out any sort of hole-like boundary (i.e., a one-way-crossing-only surface which has a spatial direction as well as being in the past) during the inflationary epoch. And we are probably already at the ruling-out point with baryon acoustic oscillation galaxy filament https://svs.gsfc.nasa.gov/13768 https://svs.gsfc.nasa.gov/13768 evidence.
  - jvanderbot 2y ago
    When I thought about white holes, I guess I thought there was a big source of energy pushing spacetime out from itself and the further you got the faster you went, basically the literal opposite of gravity. I guess I was imagining something other than what you described which is not very helpful or testable.
    - raattgift 2y ago
      You're not all that far from describing dark energy. Gravitational attraction tends to cause the trajectories of freely-falling ("floating in empty space") masses to converge. Dark energy tends to cause the trajectories of freely-falling masses to diverge. We see this in the sky: distant galaxies are freely-falling but their trajectories are away from each other (and from us). As far as we can tell though, the "source" of dark energy is the cosmological constant. Physical interpretations usually start by slicing spacetime into spaces aligned along the cosmological time (the scale factor). In successive spatial slices ordinary matter, radiation, dark matter, and so forth all get sparser towards the future. We treat these as a sort of fluid or gas that dilutes away with the expansion of the universe, therefore the density of each fluid at a typical point differs from spatial slice to spatial slice (it's lower in the future). The cosmological constant is constant in every spatial slice. So if we were to turn it into one of these fluids, it would not dilute or thin out over time: its density at a typical point is always the same. Representing a geometrical feature (the cosmological constant) as a space-filling fluid with certain properties makes it easier to study what happens if the cosmological constant isn't constant . (Does it fluctuate? Does it get weaker or stronger over time or in the presence of overdensities of matter?) Cosmic inflation introduces another of these fluids that like dark energy serves to separate rather than draw together the others. It's very very strong in the early part of the universe (the inflationary epoch), but disappears very early too. In some flavours of inflation, the "inflaton" field decays into standard-model matter; in others it just decays into weaker and weaker versions of itself and by the time there are electrons, positrons and photons it's basically so weak that it's undetectable. The inflationary epoch somewhat matches your intuition that a big source of energy pushed space apart. The most important difference (at this "explain like I'm..." level) as far as I can tell is that there was no point in space that someone in the early universe could point to as the centre or source of inflation. A gravitating object has a centre of mass, and you can point to and away from that object, i.e. there is an up and down with respect to it, because it doesn't surround you like a shell. The inflaton field was strong everywhere, there was nowhere in space "outside" it. Here is a reasonably accessible "outreach" article on cosmic inflation: https://www.ctc.cam.ac.uk/outreach/origins/inflation_zero.php https://www.ctc.cam.ac.uk/outreach/origins/inflation_zero.ph...
survirtual 2y ago
Most likely reason? Our universe originated from a white hole we refer to as the big bang.
- pdonis 2y ago
  No, the big bang is not a white hole. A white hole has an antihorizon. Our universe does not.
  - survirtual 2y ago
    Can this really be said with any certainty? If we originated from a white hole, the effects on time would be difficult to measure from inside it, wouldn't it? Do you have some proven modeling of the inside of a singularity? If so, I would be very interested in that. I haven't been to the "edge" of our expanding universe, so I can't say anything for certain. I haven't been inside the event horizon of a black hole (or have we?), so I can't claim to say what happens on the other side of it. What I do know is it'd be pretty sweet if black holes are entry ways into new universes and our universe is the exit point of some other universe and we are currently existing in an exit point among a massive chain / fabric of countless realities, all of which we are connected to. So until we build chips that can reach the edge of our universe or ships that can travel to the origin of the big bang, or come up with irrefutable and provable models of what's really happening, I'm going to go with the sweetest possibility I can imagine.
    - pdonis 2y ago
      > Can this really be said with any certainty? Yes. A white hole is not homogeneous and isotropic. Our universe is. > irrefutable and provable models of what's really happening Science can never meet this requirement, because we can never collect all possible data. But that doesn't mean we can't rule out some models. We can rule out a white hole model of our universe, for the reason I gave above.
      - survirtual 2y ago
        No, you really can’t claim definitive knowledge about singularities based on our current models. The rules—as understood through general relativity and quantum mechanics—change drastically at the scale of a singularity. No amount of observing shadows of a singularity conforming to predictions changes the ignorance regarding the interior of the singularity. Given that these conditions are fundamentally outside of our current observational capabilities and that existing theories are known to break down under such extreme conditions, it is presumptuous to apply conventional physical models developed for ‘normal’ spacetime. Until we have a unified theory of quantum gravity that is experimentally validated, any claims about the behavior within singularities remain speculative and should be treated with appropriate skepticism. Just because it appears from our reference frame that a black hole compresses to a point and a white hole emits from a point, does not mean that is the physical effect occurring from within the singularity. When dealing with infinite, the rules change. For all we know, beyond the event horizon, the environment could be as fantastical as a land made of ice cream and lollipops—where everything around is sweet and edible. Doubt that? Send a probe into the nearest black hole and somehow retrieve it. Also, locate and observe a white hole, and develop an engine with infinite thrust that can approach it. I'm sure there will be enough observational data then to make finite claims. Good luck!
MaxikCZ 2y ago
Technically, blackhole is in our future. It might be distant, but eventually we (our matter/energy) will probably fall in some. So maybe all whiteholes are in our past, and we came from one we call Big Bang.
- reaperman 2y ago
  I don't think ultimate expansion vs contraction has been conclusively proven one way or another, but if the universe is expanding and destined to end in "heat death", I'm curious what % of matter in the Milky Way would be predicted to wind up in a black hole. I see one estimate[0] of 0.1% of "all stars"/"all matter in the universe" will end up in a black hole, but obviously these estimates are subject to revision over time, and I'm more curious about our solar system specifically, which may be subject to special conditions that increase the likelihood of ending up in a black hole. Nonetheless, I suspect you are greatly overestimating the likelihood of human matter falling into a black hole. 0: https://www.forbes.com/sites/startswithabang/2019/07/02/no-black-holes-will-never-consume-the-universe/?sh=1ad9e7f61c5c https://www.forbes.com/sites/startswithabang/2019/07/02/no-b...
  - bArray 2y ago
    > I'm curious what % of matter in the Milky Way would be predicted to wind up in a black hole. I can't back this up, but my theory would be near 100% of all matter ends up back in a black hole (in a very long time). If no energy is created or destroyed, whatever force is expanding the Universe will eventually un-expand it. The alternative to me seems insane - you have a closed system with finite states (insanely large numbers of finite states) that can never return to a previous state, even after near infinite time? Doesn't add up. I'm not aware of any closed-loop system (where energy is conserved) that doesn't return back to the original state.
    - vlovich123 2y ago
      Objects in motion continue in motion. So without energy being created or destroyed, why would you expect a contraction instead of continuing expansion? Real closed loop systems are purely theoretical and the only one we know of is the Universe, so your statements about them are circular. One big unidirectional aspect of the universe is entropy - it’s a non-reversible state. Going to a previous state requires more energy than what you started with.
pdonis 2y ago
The fact that there is a mathematical solution to the Einstein Field Equation that describes a white hole does not mean white holes actually exist. There are an infinite number of solutions to any equation in physics, the vast majority of which describe things that do not exist. We have to make actual observations to find out which of the vast number of solutions do describe things that exist.

ndsipa_pomu 2y ago

Are you sure that the big bang wasn't one?

raattgift 2y ago
Yes, we can be certain. White holes can be considered in two ways: (1) a region of spacetime into which nothing can ever cross, with a surface that is a perfect reflector; or somewhat less commonly (2) a time-reversed black hole. At scales of gigaparsecs, the universe appears to be both spatially homogeneous and isotropic, with matter denser at higher redshift. There is no way to generate this configuration of matter from a white hole. White holes are very much spatially anisotropic, that is you can point to where they are: left of you but not right of you, in front of you but not behind you, etc. The trajectories of the centres of momentum of galaxy clusters in every direction and at every redshift are diverging but not following an inertial radial. The really compelling accessible evidence against a white hole big bang is in the https://en.wikipedia.org/wiki/Lyman-alpha_forest https://en.wikipedia.org/wiki/Lyman-alpha_forest from hydrogen clouds at different redshifts being backlit by bright background (and thus earlier in the universe) sources. This "stacking" is so hard to conceive for a white hole big bang that as far as I know, nobody has actually written down a reasonable explanation for it. More technically, (general relativity) metrics at those "cosmologically large" scales are so different from the metrics of white holes that we would already have noticed. Additionally, a white hole big bang has to account for the chemistry of the earliest visible stars, whose spectral lines indicate essentially hydrogen with a tiny amount of helium and lithium. The standard cosmology's big bang nucleosynthesis's chemical abundances would have to be duplicated by a white hole big bang, and as far as I know nobody knows how to make that work. How does whatever is spit out of a white hole interior, or reflected off a white hole boundary, eventually turn into atomic hydrogen (with a smattering of heavier atoms up to 7 atomic mass units)? How does it account for the cosmic microwave background, which implies that in some region of the white hole big bang universe atoms practically everywhere were so hot as to be completely ionized? Likewise, the interior metrics of black holes are very different from metrics which reasonably describe observations at gigaparsec scales. So if one takes a "wormhole" maximal extension of a black hole spacetime and throws enormous amounts matter into the black hole end, what emerges at the white hole end is nothing like a cosmology. Nor is what's inside. So a reasonable prediction of our galaxy's future is not exiting from a white hole (with us presently inside), and a reasonable prediction of our past is not that our galaxy was spit out of a white hole (with us presently outside). As far as I know, nobody has done a convincing treatment of a non-eternal white hole in General Relativity. We've had theoretical models for forming black holes (i.e., there is a past of the black hole where there is no black hole yet, so it's non-eternal) since the 1930s (<https://en.wikipedia.org/wiki/Oppenheimer%E2%80%93Snyder_model https://en.wikipedia.org/wiki/Oppenheimer%E2%80%93Snyder_mod...>), and models for evaporating black holes since Hawking 1970, so it's quite striking there's nothing similar for white holes. There is ample astrophysical evidence supporting a range of models for non-eternal black holes and their horizons. There isn't anything seen by our telescopes that looks like it might be a white hole horizon. The accelerated expansion of the universe, discovered in 1998, kills off a bunch of vaguely related ideas, like we are in a tiny tiny fraction of a thin shell (thin as in small compared to the shell's diameter) of matter that is expanding inertially from an initial impulse (an "explosion", figuratively) acting on a dense phase of matter. By "tiny tiny" here we're talking about our visible universe occupying less than 10^-23 of the shell's thickness. This is from a family of ideas tossed around a bit before Alan Guth published his 1997 book <https://en.wikipedia.org/wiki/The_Inflationary_Universe https://en.wikipedia.org/wiki/The_Inflationary_Universe>. One could imagine a reflector onto which the shell fell, and that reflector could resemble a white hole; you can get a cyclic cosmology by having the entire shell eventually reconverge on the central reflector. However, we now see the expansion of our universe is speeding up rather than slowing down, so this doesn't work. Finally, we're learning a lot more about the gravitational wave background of our universe. It is reasonable to bet that studies of the polarization of the cosmic microwave background (e.g. <https://lweb.cfa.harvard.edu/~cbischoff/bicepkeck/ https://lweb.cfa.harvard.edu/~cbischoff/bicepkeck/>) will find evidence of gravitational waves at scales large enough and uniform enough to rule out any sort of hole-like boundary (i.e., a one-way-crossing-only surface which has a spatial direction as well as being in the past) during the inflationary epoch. And we are probably already at the ruling-out point with baryon acoustic oscillation galaxy filament https://svs.gsfc.nasa.gov/13768 https://svs.gsfc.nasa.gov/13768 evidence.
- jvanderbot 2y ago
  When I thought about white holes, I guess I thought there was a big source of energy pushing spacetime out from itself and the further you got the faster you went, basically the literal opposite of gravity. I guess I was imagining something other than what you described which is not very helpful or testable.
  - raattgift 2y ago
    You're not all that far from describing dark energy. Gravitational attraction tends to cause the trajectories of freely-falling ("floating in empty space") masses to converge. Dark energy tends to cause the trajectories of freely-falling masses to diverge. We see this in the sky: distant galaxies are freely-falling but their trajectories are away from each other (and from us). As far as we can tell though, the "source" of dark energy is the cosmological constant. Physical interpretations usually start by slicing spacetime into spaces aligned along the cosmological time (the scale factor). In successive spatial slices ordinary matter, radiation, dark matter, and so forth all get sparser towards the future. We treat these as a sort of fluid or gas that dilutes away with the expansion of the universe, therefore the density of each fluid at a typical point differs from spatial slice to spatial slice (it's lower in the future). The cosmological constant is constant in every spatial slice. So if we were to turn it into one of these fluids, it would not dilute or thin out over time: its density at a typical point is always the same. Representing a geometrical feature (the cosmological constant) as a space-filling fluid with certain properties makes it easier to study what happens if the cosmological constant isn't constant . (Does it fluctuate? Does it get weaker or stronger over time or in the presence of overdensities of matter?) Cosmic inflation introduces another of these fluids that like dark energy serves to separate rather than draw together the others. It's very very strong in the early part of the universe (the inflationary epoch), but disappears very early too. In some flavours of inflation, the "inflaton" field decays into standard-model matter; in others it just decays into weaker and weaker versions of itself and by the time there are electrons, positrons and photons it's basically so weak that it's undetectable. The inflationary epoch somewhat matches your intuition that a big source of energy pushed space apart. The most important difference (at this "explain like I'm..." level) as far as I can tell is that there was no point in space that someone in the early universe could point to as the centre or source of inflation. A gravitating object has a centre of mass, and you can point to and away from that object, i.e. there is an up and down with respect to it, because it doesn't surround you like a shell. The inflaton field was strong everywhere, there was nowhere in space "outside" it. Here is a reasonably accessible "outreach" article on cosmic inflation: https://www.ctc.cam.ac.uk/outreach/origins/inflation_zero.php https://www.ctc.cam.ac.uk/outreach/origins/inflation_zero.ph...

survirtual 2y ago

Most likely reason? Our universe originated from a white hole we refer to as the big bang.

pdonis 2y ago
No, the big bang is not a white hole. A white hole has an antihorizon. Our universe does not.
- survirtual 2y ago
  Can this really be said with any certainty? If we originated from a white hole, the effects on time would be difficult to measure from inside it, wouldn't it? Do you have some proven modeling of the inside of a singularity? If so, I would be very interested in that. I haven't been to the "edge" of our expanding universe, so I can't say anything for certain. I haven't been inside the event horizon of a black hole (or have we?), so I can't claim to say what happens on the other side of it. What I do know is it'd be pretty sweet if black holes are entry ways into new universes and our universe is the exit point of some other universe and we are currently existing in an exit point among a massive chain / fabric of countless realities, all of which we are connected to. So until we build chips that can reach the edge of our universe or ships that can travel to the origin of the big bang, or come up with irrefutable and provable models of what's really happening, I'm going to go with the sweetest possibility I can imagine.
  - pdonis 2y ago
    > Can this really be said with any certainty? Yes. A white hole is not homogeneous and isotropic. Our universe is. > irrefutable and provable models of what's really happening Science can never meet this requirement, because we can never collect all possible data. But that doesn't mean we can't rule out some models. We can rule out a white hole model of our universe, for the reason I gave above.
    - survirtual 2y ago
      No, you really can’t claim definitive knowledge about singularities based on our current models. The rules—as understood through general relativity and quantum mechanics—change drastically at the scale of a singularity. No amount of observing shadows of a singularity conforming to predictions changes the ignorance regarding the interior of the singularity. Given that these conditions are fundamentally outside of our current observational capabilities and that existing theories are known to break down under such extreme conditions, it is presumptuous to apply conventional physical models developed for ‘normal’ spacetime. Until we have a unified theory of quantum gravity that is experimentally validated, any claims about the behavior within singularities remain speculative and should be treated with appropriate skepticism. Just because it appears from our reference frame that a black hole compresses to a point and a white hole emits from a point, does not mean that is the physical effect occurring from within the singularity. When dealing with infinite, the rules change. For all we know, beyond the event horizon, the environment could be as fantastical as a land made of ice cream and lollipops—where everything around is sweet and edible. Doubt that? Send a probe into the nearest black hole and somehow retrieve it. Also, locate and observe a white hole, and develop an engine with infinite thrust that can approach it. I'm sure there will be enough observational data then to make finite claims. Good luck!

MaxikCZ 2y ago

Technically, blackhole is in our future. It might be distant, but eventually we (our matter/energy) will probably fall in some. So maybe all whiteholes are in our past, and we came from one we call Big Bang.

reaperman 2y ago
I don't think ultimate expansion vs contraction has been conclusively proven one way or another, but if the universe is expanding and destined to end in "heat death", I'm curious what % of matter in the Milky Way would be predicted to wind up in a black hole. I see one estimate[0] of 0.1% of "all stars"/"all matter in the universe" will end up in a black hole, but obviously these estimates are subject to revision over time, and I'm more curious about our solar system specifically, which may be subject to special conditions that increase the likelihood of ending up in a black hole. Nonetheless, I suspect you are greatly overestimating the likelihood of human matter falling into a black hole. 0: https://www.forbes.com/sites/startswithabang/2019/07/02/no-black-holes-will-never-consume-the-universe/?sh=1ad9e7f61c5c https://www.forbes.com/sites/startswithabang/2019/07/02/no-b...
- bArray 2y ago
  > I'm curious what % of matter in the Milky Way would be predicted to wind up in a black hole. I can't back this up, but my theory would be near 100% of all matter ends up back in a black hole (in a very long time). If no energy is created or destroyed, whatever force is expanding the Universe will eventually un-expand it. The alternative to me seems insane - you have a closed system with finite states (insanely large numbers of finite states) that can never return to a previous state, even after near infinite time? Doesn't add up. I'm not aware of any closed-loop system (where energy is conserved) that doesn't return back to the original state.
  - vlovich123 2y ago
    Objects in motion continue in motion. So without energy being created or destroyed, why would you expect a contraction instead of continuing expansion? Real closed loop systems are purely theoretical and the only one we know of is the Universe, so your statements about them are circular. One big unidirectional aspect of the universe is entropy - it’s a non-reversible state. Going to a previous state requires more energy than what you started with.

pdonis 2y ago

The fact that there is a mathematical solution to the Einstein Field Equation that describes a white hole does not mean white holes actually exist. There are an infinite number of solutions to any equation in physics, the vast majority of which describe things that do not exist. We have to make actual observations to find out which of the vast number of solutions do describe things that exist.