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chasil 18 hours ago [-]
I understand that, for a stationary black hole without spin (which does not exist), an object that falls into it will freeze, then the image will redshift until it disappears.
I also understand that there is a cosmological (event) horizon, where galaxies freeze, then rapidly redshift in the same way. This happens because these distant objects are accelerated away from us faster than light.
It appears to me that we are seeing black hole event horizons from the outside, and the cosmological event horizon is seen from the inside.
The similarities do give one pause.
The mechanisms are different; one is gravity, and the other is dark energy.
I mean they’re similar because it’s the same thing happening… light not being able to reach us.
cryptonector 21 hours ago [-]
Edward Arthur Milne's proposal was that the universe started out expanding. That is Milne cosmology, and oddly enough it's equivalent to Standard cosmology when you take out the gravitational effects of mass-energy. What's odd about that is that in Milne cosmology you have a big bang at one point with the edge moving at arbitrarily close to c and with uniform distribution of stuff and velocities, while in Standard cosmology we speak of the big bang happening everywhere all at once. This oddity is resolved when you realize that Milne is hyperbolic, so you if you "unfurl" a Milne universe it then looks the same as Standard excluding gravity.
mellosouls 16 hours ago [-]
Note this website appears to be based around the personal theories of a scientist rather than a presentation of the consensus of the field.
Perhaps similar to somebody more famous like Harari in that respect.
The author appears to be legitimate in his scientific background but the repeated implications of the revolutionary nature of his work are somewhat crankish; this is a personal blog so possibly he just needs a good editor (he says he is published elsewhere).
Just something to bear in mind as you read - not that there isn't anything to gain from it; but the boundary between well-grounded theory and speculative philosophic beliefs may not be clear - which to be fair arguably comes somewhat with the territory here.
lolakutty 15 hours ago [-]
>between well-grounded theory...
But how is the "dials" that the author describes, which "science" use to make the theory fit the facts of observation, more grounded?
mellosouls 4 hours ago [-]
I'm not sure what you mean or why you have science in quotation marks.
I think he is trying to say that the fewer things we need to tune the better, but if so that's trivially Occam's razor and a standard part of the scientific toolkit.
jungturk 16 hours ago [-]
[dead]
BoiledCabbage 19 hours ago [-]
Because our universe is actually the inside of a blackhole.
What the Wikipedia article calls "evidence" is not actually evidence. It's not things we actually observe that are predicted by this model. It's just stuff that can be made to sound plausible in the model, if you assume for the sake of argument that the model is true.
And there is also one huge reason to not think such models are viable. The Wikipedia article skates right by it:
"According to such scenarios, our observable universe was born in a black hole existing in a larger universe, where this black hole may, at some point, appear as a white hole."
The problem with this is, a white hole has a past horizon. In other words, it is an isolated system with a horizon around it, and infinite empty space outside the horizon. We have no evidence for any such thing, and how would it be possible anyway? The past horizon would have had to be "built in" to the universe from the start. It's not something that can be produced by a physical process, the way a black hole, with its future horizon, can be formed by gravitational collapse.
cryptonector 39 minutes ago [-]
Not so. You can have high enough mass-energy density and yet not a black hole because the momenta are all outward -- dynamics details matter.
dataflow 19 hours ago [-]
I'd heard that hypothesis, but not that we seem to have evidence for it too.
Absolutely wild, thanks for sharing.
> Any model of the observable universe being the interior of a black hole requires that the Hubble radius of the universe be equal to its Schwarzschild radius, which is proportional to its mass. This is indeed observed to be nearly satisfied, but might be a coincidence.
> The only way to test the idea that black holes create new universes is to measure the observable universe. Inflation generated by spin and torsion is consistent with the cosmic microwave background data from the Planck satellite.
There is a video with John Baez and Philip Gibbs explaining why this is a common misconception. It's the same family of conceptual error, where things lining up just right allow incorrect conceptual reasoning to land at a correct answer shape, that allowed John Michell to work out the Schwarzschild radius of a star in the late 1700s.
With the blackhole universe picture, causal boundaries and spacetime's evolution aren't properly accounted for once we step out of a static picture.
Incidentally, the cosmic object we are more likely to be inside of is a white-hole.
Why there are anothder blackhole? Is there blackhole inside our blackhole?
daishi55 18 hours ago [-]
Whew, really fantastic article!
> “In physics, description is explanation” (author quoting his PhD advisor)
Yes, i have always hated this about physics. It is the only scientific field that apparently feels no responsibility to explain “why”, deciding that “what” is sufficient.
I wish the author all success so that i can someday read a satisfying answer to some of the “whys” of physics.
Maxatar 17 hours ago [-]
It's not that physics feels no responsibility to explain why, it's that all other fields of science answer the why by punting to some lower level of science that is taken as an assumption until you get down to physics which has nothing lower level to punt to.
Psychology explains why you feel tired by pointing to biology. Biology explains why cells need ATP by pointing to chemistry. Chemistry explains why ATP releases energy by pointing to physics. Physics explains that by pointing to some higher level form of physics like thermodynamics, which points to statistical mechanics, which point to quantum laws. When you get down to a certain level you simply have nothing left to punt to. You simply accept it because it's what's observed and makes reproducible predictions or you don't and go study philosophy or religion or something.
daishi55 5 hours ago [-]
Yeah you’re right. And also part of it is that I simply don’t know enough deep physics to maybe start to get a more “intuitive” grasp on things.
But on the other hand I do feel there are cases where other fields have true explanations without punting. It’s not all the time but sometimes. My favorite example is evolution. We observe evidence that species evolve over long periods. Why? Natural selection. It’s the entire explanation. And I suppose in some senses it punts on the mechanisms of natural selection - genes and molecular biology rest on physics and chemistry after all. But in terms of the why, why does evolution happen, I feel we have a complete answer that has that feeling of intellectual satisfaction and completeness that is, at least from my lay perspective, lacking in physics.
lolakutty 15 hours ago [-]
There is philosophy, but common physicists does not like going there, unless for rare cases like the author or Max Tegmark or Roger Penrose...
So they goes round and round, using more and more "dials" to stay within their framework, always kicking the can down the road a bit (its turtles all the way down), but never really answering the core questions...
ishouldstayaway 14 hours ago [-]
Or, as the old joke goes:
> Psychology is really biology; biology is really chemistry; chemistry is really physics; physics is really math; and math is really hard.
BearOso 20 hours ago [-]
I kind of like the idea that as the edge of the universe is observed, it expands to fit that observation. "Observed" being in the same sense as the uncertainty principle. But there's also the idea of the universe or space as a kind of mesh that's stretching, not really growing.
When I think about things at this scale, it really makes me feel minuscule.
z2 18 hours ago [-]
I've always thought it would be interesting if the universe also operated on the principles of lazy evaluation, and the deeper you point the telescope, the more is rendered.
That or that it's all a fractal!
marcus_holmes 16 hours ago [-]
I like that too. It fits with the "there's no such thing as infinity, there's just really big numbers". So space is not infinite, it just doesn't have edges.
bionhoward 15 hours ago [-]
I feel cosmology ought to grapple more with, “Why is there something rather than nothing?” That question and this question are certainly linked. If expansion is a mirror of collapse, how do we get from some initial nothingness to a point where there is something capable of collapsing? Starting with an infinite amount of stuff everywhere feels like cheating.
cgio 13 hours ago [-]
But that’s cosmogony, not cosmology. Cosmology can just explore the cosmos that is there not having to worry about why it came to be. If there’s a causality of causality, then what’s the cause of itself.
jan_m_savage 18 hours ago [-]
Attempts to tackle why in science are actually, underneath, just a how-it-really-happens, or what-happens answers.
No scientist can explain the why, and most can't even explain the how (Heisenberg uncertainty, for one accessible example).
jan_m_savage 15 hours ago [-]
The fact that i am being downvoted on my previous comment means i am on to sth. Truth maybe?
lolakutty 15 hours ago [-]
I didn't really understand what you wrote in your comment above. Re-phrase a bit maybe?
api 19 hours ago [-]
My favorite idea is that the universe expands because mass-energy in our 4d parent universe is falling into our universe, which is a black hole. We exist as information upon the 4d hole’s 3d event horizon, and experience its inflation as our time dimension (as well as space inflation).
Inflation is accelerating because as the black hole grows it eats more.
Don’t know how crackpot this is. From what I’ve read it actually can be coaxed into fitting observation but there’s just no possible way to test it.
0x20cowboy 19 hours ago [-]
It’s not expanding. It’s rotating in the 4th dimension.
jagged-chisel 18 hours ago [-]
Tomayto, tomahto? Mathematically speaking, I mean.
eisvogel 16 hours ago [-]
I doubt very much the universe is expanding. The CMB doesn't present as a uniform field and is probably just noise from galaxies. There is too much vested religious interest in a finite and non-eternal universe for preconceptions not to cloud scientific observation. I call bullshit.
phamduongtria 14 hours ago [-]
to have enough space to accommodate your mom … I’m so sorry for this joke
m3kw9 16 hours ago [-]
is pointless to say the universe expands. We don't even know where it ends or begins
snarkconjecture 20 hours ago [-]
> The standard cosmological model affords no such explanation
Einstein GR → Friedmann eqns → universe can be expanding or contracting
Rest of this amounts to "what about initial conditions? things become divergent at t→0"
Yes, this is called the Big Bang singularity, GR breaks down there. You are not the first person to notice this. It is considered one of the biggest open problems in the field.
The stuff about accelerating expansion is confused (AI?) slop which eventually gets around to admitting that there's no problem at t>0 and no change to the existing problem at t=0, so I don't know why you didn't just cut it.
This is some real "unsolicited snail mail to physics departments"-tier content, even for HN I think it's embarrassing to have this on the front page.
I guess because every code monkey in Silicon Valley has wet dreams about overthrowing the hidebound physics establishment for some reason
lolakutty 15 hours ago [-]
>unsolicited snail mail to physics departments..
Would Ramanujan's unsolicited letter to Hardy be one of the kind that you describe here?
LastTrain 20 hours ago [-]
Dunning Krueger is most prevalent in software engineers for some reason. Fortunately most of us grow out of it and begin to appreciate how hard other disciplines are.
pdonis 18 hours ago [-]
One red flag that jumped out at me was, not a single link to a published paper, or even an arxiv preprint. Just other blog posts. Actual physics isn't done in blog posts. What has actually been published about all this for other physicists to critique? It's easy to make anything sound plausible if no one else but you gets to speak.
lolakutty 15 hours ago [-]
Probably because physicists are not going to entertain stuff that is trying to get them out of their comfort zone...
pdonis 18 hours ago [-]
> this is called the Big Bang singularity, GR breaks down there.
Only in models that actually have such an initial singularity. Not all models do. Eternal inflation models, for example, do not.
layer8 18 hours ago [-]
Physics/cosmology-related HN submissions tend to have poor comment quality, so this being upvoted to the front page isn’t too surprising, unfortunately.
redwood 19 hours ago [-]
What stuff about accelerating expansion are you referring to? The author is a physicist not just a barstool talker. He's right as you point out that there are huge interesting and unexplained phenomena that sometimes have pretty little names that discourage further question asking. It's sad to see such negativity instead of engaging with the material a bit
pdonis 18 hours ago [-]
> The author is a physicist
While this is true, it's also true that out of all of his published work in physics (which you can find at the "Google Scholar" link on the Author page of his log), none of it, as far as I can see, is about the hypothesis described in this article. All his writings about that appear on his blog. Which means that, if he has tried to get any of this published in peer-reviewed journals, he's failed.
This could mean that he is a visionary whose insight is not recognized by the establishment, which is the story he tells. It could also mean that his speculations actually don't lead anywhere useful. My Bayesian prior is heavily on the latter.
lolakutty 15 hours ago [-]
Why do you have to use your statistics, when you can use arguments addressing the problems in the articles?
Sounds lot like you are using appeal to authority.
Henchman21 18 hours ago [-]
> I guess because every code monkey in Silicon Valley has wet dreams about overthrowing the hidebound physics establishment for some reason
Too much focus on the tech in Star Trek when you're a kid, I imagine. Shoulda focused on the morality.
https://en.wikipedia.org/wiki/Event_horizon
I also understand that there is a cosmological (event) horizon, where galaxies freeze, then rapidly redshift in the same way. This happens because these distant objects are accelerated away from us faster than light.
It appears to me that we are seeing black hole event horizons from the outside, and the cosmological event horizon is seen from the inside.
The similarities do give one pause.
The mechanisms are different; one is gravity, and the other is dark energy.
https://en.wikipedia.org/wiki/Cosmological_horizon
Perhaps similar to somebody more famous like Harari in that respect.
The author appears to be legitimate in his scientific background but the repeated implications of the revolutionary nature of his work are somewhat crankish; this is a personal blog so possibly he just needs a good editor (he says he is published elsewhere).
Just something to bear in mind as you read - not that there isn't anything to gain from it; but the boundary between well-grounded theory and speculative philosophic beliefs may not be clear - which to be fair arguably comes somewhat with the territory here.
But how is the "dials" that the author describes, which "science" use to make the theory fit the facts of observation, more grounded?
I think he is trying to say that the fewer things we need to tune the better, but if so that's trivially Occam's razor and a standard part of the scientific toolkit.
https://en.wikipedia.org/wiki/Black_hole_cosmology#Evidence
And there is also one huge reason to not think such models are viable. The Wikipedia article skates right by it:
"According to such scenarios, our observable universe was born in a black hole existing in a larger universe, where this black hole may, at some point, appear as a white hole."
The problem with this is, a white hole has a past horizon. In other words, it is an isolated system with a horizon around it, and infinite empty space outside the horizon. We have no evidence for any such thing, and how would it be possible anyway? The past horizon would have had to be "built in" to the universe from the start. It's not something that can be produced by a physical process, the way a black hole, with its future horizon, can be formed by gravitational collapse.
Absolutely wild, thanks for sharing.
> Any model of the observable universe being the interior of a black hole requires that the Hubble radius of the universe be equal to its Schwarzschild radius, which is proportional to its mass. This is indeed observed to be nearly satisfied, but might be a coincidence.
> The only way to test the idea that black holes create new universes is to measure the observable universe. Inflation generated by spin and torsion is consistent with the cosmic microwave background data from the Planck satellite.
With the blackhole universe picture, causal boundaries and spacetime's evolution aren't properly accounted for once we step out of a static picture.
Incidentally, the cosmic object we are more likely to be inside of is a white-hole.
https://www.youtube.com/watch?v=ULjLGTd3-4s
So what then, is it black holes all the way down?
> “In physics, description is explanation” (author quoting his PhD advisor)
Yes, i have always hated this about physics. It is the only scientific field that apparently feels no responsibility to explain “why”, deciding that “what” is sufficient.
I wish the author all success so that i can someday read a satisfying answer to some of the “whys” of physics.
Psychology explains why you feel tired by pointing to biology. Biology explains why cells need ATP by pointing to chemistry. Chemistry explains why ATP releases energy by pointing to physics. Physics explains that by pointing to some higher level form of physics like thermodynamics, which points to statistical mechanics, which point to quantum laws. When you get down to a certain level you simply have nothing left to punt to. You simply accept it because it's what's observed and makes reproducible predictions or you don't and go study philosophy or religion or something.
But on the other hand I do feel there are cases where other fields have true explanations without punting. It’s not all the time but sometimes. My favorite example is evolution. We observe evidence that species evolve over long periods. Why? Natural selection. It’s the entire explanation. And I suppose in some senses it punts on the mechanisms of natural selection - genes and molecular biology rest on physics and chemistry after all. But in terms of the why, why does evolution happen, I feel we have a complete answer that has that feeling of intellectual satisfaction and completeness that is, at least from my lay perspective, lacking in physics.
So they goes round and round, using more and more "dials" to stay within their framework, always kicking the can down the road a bit (its turtles all the way down), but never really answering the core questions...
> Psychology is really biology; biology is really chemistry; chemistry is really physics; physics is really math; and math is really hard.
When I think about things at this scale, it really makes me feel minuscule.
That or that it's all a fractal!
No scientist can explain the why, and most can't even explain the how (Heisenberg uncertainty, for one accessible example).
Inflation is accelerating because as the black hole grows it eats more.
Don’t know how crackpot this is. From what I’ve read it actually can be coaxed into fitting observation but there’s just no possible way to test it.
Einstein GR → Friedmann eqns → universe can be expanding or contracting
Rest of this amounts to "what about initial conditions? things become divergent at t→0"
Yes, this is called the Big Bang singularity, GR breaks down there. You are not the first person to notice this. It is considered one of the biggest open problems in the field.
The stuff about accelerating expansion is confused (AI?) slop which eventually gets around to admitting that there's no problem at t>0 and no change to the existing problem at t=0, so I don't know why you didn't just cut it.
This is some real "unsolicited snail mail to physics departments"-tier content, even for HN I think it's embarrassing to have this on the front page.
I guess because every code monkey in Silicon Valley has wet dreams about overthrowing the hidebound physics establishment for some reason
Would Ramanujan's unsolicited letter to Hardy be one of the kind that you describe here?
Only in models that actually have such an initial singularity. Not all models do. Eternal inflation models, for example, do not.
While this is true, it's also true that out of all of his published work in physics (which you can find at the "Google Scholar" link on the Author page of his log), none of it, as far as I can see, is about the hypothesis described in this article. All his writings about that appear on his blog. Which means that, if he has tried to get any of this published in peer-reviewed journals, he's failed.
This could mean that he is a visionary whose insight is not recognized by the establishment, which is the story he tells. It could also mean that his speculations actually don't lead anywhere useful. My Bayesian prior is heavily on the latter.
Sounds lot like you are using appeal to authority.
Too much focus on the tech in Star Trek when you're a kid, I imagine. Shoulda focused on the morality.