"Science is prediction, not explanation" - Fred Hoyle.
But isn't this effectively saying that the dimensions-based model for universe is incorrect? I'm trying to understand the comparison when it seems to be saying the benchmark is wrong.
After reading the article and not understanding anything, I thought maybe someone at HN made more sense if it than me, so I checked the comments.
Glad to know I'm not the only one for whom this was incomprehensible!
What we have - the space of possible states, i.e. entropy, inside a black hole has significantly reduced cardinality, i.e. it is equivalent to the cardinality of the black hole surface in this case. That means that either there is strong additional dependency/correlation arises between the states of the black hole components/particles (doesn't sound that unrealistic - we do have similar, using very wide notion of similarity of course :), process on the other side of the spectrum - Bose-Einstein condensate (and the similarity may be pretty high https://arxiv.org/pdf/0807.0315.pdf)), and which in effect is kind of equivalent to the loss of some degrees of freedom, or may be there is a loss of degrees of freedom due to the black hole spacetime distortion - gravity distorts the spacetime, and the black hole is the ultimate case of it with the local time basically disappearing for the external observer, and thus we have a perceived loss of degrees of freedom - as observed by external observer. I.e. it may as well be that the entropy inside, as would be perceived locally, may still be "normal 3D" in the local spacetime while it is basically frozen from the POV of external observer (and thus what we observe is the projection of the rest of that spacetime taken at the point where(when) a given dimension is "stuck"), and thus externally observed "2D" entropy is just stuck in time, ie. a projection of, the "normal" 3D entropy of the black hole insides. Drawing some parallel with light coming out of deep gravitational well - the lightwave is stretching like the time dimension is getting "slower" until it stops in the case of black hole. The stopped dimension and an absence of the dimension - not much difference math- and observation-wise.
'Hologram' just seems to be a loose analogy for the concept that 'something complex came from something simple.'
On the other hand, the holographic nail sounds pretty neat.
Think about where Classical Physics breaks down (at the big bang and black holes/singularity).
So if you, as a higher dimensional being, fall into a black hole (a lower dimensional space) where does all that higher dimensional information go? Well like a hologram, the idea is the information gets recorded on the surface of a black hole, or event horizon. In short its like a 3D object being able to exist in/on a 2D plain.
If a hologram doesn't work for you, maybe try thinking about fractal geometry where the perimeter of an object can measure infinity while simultaneously the volume is perfectly measurable and well defined.
It's unclear what is so important about the 'hologram'.
What they really seem to be trying to do is explain how we get something from nothing, with ever more convoluted mathematical abstractions to try and avoid the inherent logical contradiction.
Seriously though, look up how holograms work. There's a lot of thought provoking aspects to them and it's no wonder they've inspired a lot of novel thought about the nature of the universe.
Yes according to Einstein we on a smooth fabric of spacetime that curves in the presence of these 3D objects...but Quantum Mechanics isn't such a smooth universe as you scale downward.
The reason a hologram is interesting is that each of its parts contains the whole. Above book by Michael Talbot is a good introduction to the topic.