Ask HN: Is it black holes all the way up?

Contrary to popular belief, black holes do not "suck up everything". The same way the sun does not "suck up everything" in our solar system. Sure, if stuff keeps colliding with the black hole, the black hole gets bigger and bigger (the same way the sun would get bigger and bigger if enough mass would fall into it). But the black hole never turns into a giant universe-eating vacuum cleaner, the same way the sun doesn't "eat" everything that gets close to it (e.g. comets pass very close but still get away... the same would happen if the sun were a black hole, and at the same distance, since the mass is the same)

On the contrary, due to the expansion of the universe, stuff tends to move further and further away from other stuff over time, so the chances of things colliding with a black hole get smaller and smaller with the age of the universe. At some point all black holes evaporate (at least according to current theories) because so little stuff falls into them that the tiny amount of hawking radiation that they radiate is enough to evaporate them over trillions of years.....

Also, the question whether "a universe before the big bang" (if such a thing exists) is "the same" as ours, or "different", doesn't really make sense. If you take all matter in the universe, heat it up so that only high-energy radiation is left, and then let it "create another universe"... . how would you define if it's "the same" or "different"? All matter has been removed and recreated. It's similar to the idea that you take a ship, any ship, and piece by piece replace every single part of the ship one by one. At the end, is it still the same ship or a different one?

To take a more traditional scientific stance, asking "what happened before the big bang" is meaningless because time didn't exist, it was created by the big bang. It's tricky to wrap your head around the concept, the same way that it's tricky to wrap your head around the concept of an "expanding universe" that seems to expand "away" from us in every direction, yet we are not in the center of it. Or that the universe might be infinitely large or even wrap around, yet we will never know because we can only ever "look" 14 billion light years far into the universe. It could be that after travelling for 20 billion light years we wouldn't reach the end of the universe (because it has no end) but instead land back on earth.

Some questions can never be answered because of physics. They will forever be unknown because answering them either makes no sense, or none of the answers you could give could ever be verified/falsified. So: does asking these questions even make sense?

This is very interesting - thank you for sending. His "cyclic cosmology" somewhat fits into 2 but with a different flavor. And given you reach a stage of maximum entropy during the heat death of the universe prior to folding back into a new singularity - it seems the same result would still occur each time given no changes in initial conditions.

I'm sort of leaning towards LinuxBender here in thinking this is all some infinite movie on loop generated bc consciousness was bored by itself in the dark.

I think asking the question makes sense even if the answer is "no answer". It's interesting to think about and to explore, and helpful to get the input of others.

By the "sameness" point - I mean that in a deterministic universe where initial conditions are precisely the same, that the same universe structure will continue to arise and play out over and over again (putting aside quantum uncertainty). While the "ship" may not be the "same" ship, it will still be a ship and not a refrigerator.

> If the conditions at the bottom of two black hole "singularity"s are the same - you would expect parallel, equal universes to be generated each time.

That's a strong no (for any sufficiently complex physical setup with moving parts, falling glasses won't shatter the same way twice).

Two things here are relevant:

1) Lorentz (Butterfly) and Smale (Horseshoe Map) both proved that in some physical systems you can always find initial conditions that are very close (for any arbitary epsilon of "close") that none the less end up far away from each other as time passes.

ie: Unless the initial starting points are absolutely precisely identical without question, then "close enough" isn't good enough to guarentee an identical outcome in the presence of "strange attractors"

2) The Uncertainty Principle tells us that at a fine enough grain (within a certain epsilon) initial conditions are like jelly - you cannot nail them to the wall and declare two systems identical.

Yes, note that I say the equal universes situation only occurs if the conditions are the same (which I agree is unlikely). They would have to be exactly the same to result in copy universes given even the slightest variation in initial conditions would compound into vastly different outcomes.

I think, in the black holes example this outcome is unlikely given even slightly more matter or quarks absorbed would differentiate the system. This would be the "parallelish" outcomes where slightly differences would compound over time. But if there's a limiting condition that only allows for one starting point, then you get the same duplicate outcomes.

In the same way that certain elements consistently arise as a result of fusion in a star, perhaps the same types of universes might arise here. You might have a "Hydrogen" universe, a "Helium" universe, an "Iron" universe dependent on the threshold that initiates a certain "big bang" / that create initial starting points that are "absolutely, precisely identical without question". This is a bit out there, probably wrong. I have no idea.

I'm not sure I'm explaining my thinking very well, but if only so much energy / matter can break through the other side of a black hole and it breaks through in the same way every time then you would get parallel, equal universes.

I am a huge fan of your usage of chaos theory to address this question - I appreciate it.