[kosh2]

I have two problems / questions with this:

1. This theory requires a parent universe that can't have been formed inside a black hole. This means there must a be second "universe creation" mechanism that we can / may never know about from our child universe. For me, this doesn't really answer the true question: "How did our universe begin?" Yeah, it may the "unknown field with strange properties" but instead we get an unknown parent universe with strange properties.

2. The black hole in the parent universe must be much much bigger than anything we see in ours since it has to contain all the matter that we see. How is a black hole supposed to form that is 750 billion times bigger than the largest black hole we know about?

[PaulHoule]

I don't see this idea as very new.

There are many models of black holes, such as the Schwarzchild solution, that have an area of "asymptotically flat spacetime" which is, from the viewpoint of our universe, part of the black hole. That something happens around the singularity that creates this new universe doesn't sound that crazy.

If our universe is a child of another universe and that is a child of another universe and so forth it fits into the kind of "multiverse" model that addresses issues such as "why does the universe have the parameters it does?" Either there are a huge amount of universes such that we're lucky to be in one we can live in, or there is some kind of natural selection such that universes that create more black holes have more children.

As for the relative size of the parent black hole, conservation of energy doesn't have to hold for universes in the normal sense. One idea is that the gravitational binding energy of the universe is equal to the opposite of all the mass in the universe such that it all adds up to zero so we could have more or less of it without violating anything.

[corry]

Do you find the idea of an infinite regress -- "our universe is a child of another universe and that is a child of another universe and so forth" -- holds much explanatory power for you?

To me it's prima facie a hollow explanation. I get that some models, like eternal inflation or certain cyclic cosmologies, entertain the idea of an infinite past or blur the standard arrow of time... but how does pushing the origin question back indefinitely actually resolve anything?

[blamestross]

The problem is that:

- We have a parent universe we will never be able to observe.

could be a true statement.

The "infinite sequence" part is just a likely implication, it isn't necessarily true. We would need information we can't access to find out.

[lugu]

I doubt you understand what science is about. The proposed theory, like any theory, should be judged on its power of prediction and simplicity. It doesn't matter if it doesn't satisfy your curiosity.

[nsonha]

where is the "prediction and simplicity" part in this theory?

[jama211]

Well said

[nurettin]

> "why does the universe have the parameters it does?"

To those who say "oh but if this parameter was slightly off, that thing I subjectively decided to pick wouldn't have happened!":

How would you know that this universe could exist in any other way? Wouldn't things just stabilize into certain frequencies and lengths after some time?

To me "fine tuning" isn't really a conundrum, it is just question begging and you don't need to wish it away with multiverses.

[D-Coder]

> we're lucky to be in one we can live in

Nitpick: We couldn't be anywhere else, except nonexistent.

[thomasweiser]

The anthropic principle

[godelski]

  > requires a parent universe

Not exactly. A universe can expand, slow down, then collapse. In this case, bouncing back out.

Does that repeat forever? Does it lose energy in the bounce? If so, to where and how?

  > The black hole in the parent universe must be much much bigger than anything we see in ours

Yes and no. You're not thinking about contraction. With relativity we can fit a 100ft ladder inside a 10ft barn.

Most importantly, you don't need everything all figured out at once to publish. Then no one would always publish. There'd be nothing to improve on. Only one publication that says everything. Till then, everything does have criticisms and is incomplete. It's good to have criticisms! They lead you to the next work!

[mcswell]

>> The black hole in the parent universe must be much much bigger than >> anything we see in ours

>> Yes and no. You're not thinking about contraction. With relativity >> we can fit a 100ft ladder inside a 10ft barn.

I believe the OP was talking about mass, not linear dimension. (And if he wasn't, I am.) Unless somehow mass inside a black hole is not constant? (ignoring accretion)

[godelski]

Relativity applies to mass too. Accelerate and you become heavier.

Remember, mathematically, a blackhole is mass in an infinitely small point. You are dividing by 0. I don't know the answer, but if someone is saying that from the outside the apparent mass is different than from the inside, that doesn't set off any alarm bells. We literally are talking about Dr Who style "it's bigger on the inside". Even the ladder example should make you think about mass. Without relativistic effects the mass inside the barn is only part of the ladder. With relativity, the whole ladder, and thus mass, is inside. So yeah, weird things happen.

[blamestross]

*aparent mass goes up

Things don't get more mass, they just take more energy to accelerate which looks a lot like more mass.

It doesn't imply for example, a high speed mass would cause more gravitational attraction than a slow one.

If that was the case, a black hole would be even worse as it accelerates matter towards itself and it gains "bonus mass"

[kosh2]

Black holes have the same mass and information as the stars that formed them.

Unless the theory also breaks mass and information conservation, the star that gave birth to our black hole must have been as massive as our entire universe.

I doubt we have any theory how a star that size can have formed.

[godelski]

I meant apparent mass. Just dropped the apparent because we're on HN and anyone familiar with relativity is likely going to know what I mean. I mean if actual mass went up we'd be violating conservation of energy. It's all about your frame of reference and you can treat these things as local systems.

[2OEH8eoCRo0]

Where does the information of the previous universe before the bounce go? Is it destroyed?

[JKCalhoun]

It's been suggested it is gone and that perhaps even new laws of physics are created with each iteration (but I don't know why that would be).

[blamestross]

Cosmic Background Radiation distribution could be that information. The distribution of mass hitting the event horizon then bouncing

[mordae]

Maybe we live inside an universal hash function.

[meowky]

1. It is possible that every universe is formed in a blackhole – an infinite universe-blackhole-universe chain. We don’t know what “infinity” means in this scenario, so we can’t simply rule it out. For comparison, Aristotle ruled out an infinite chain of causes, which we now know (with the help of hindsight, of course) is a flawed conclusion.

2. We don’t know whether our universe is big or small compared with other universes. We don’t know whether, or how, it makes sense to compare sizes between universes.

Big Bang is arguably the biggest speculation in modern science.

[mr_toad]

The outer universe could have always existed, but unlike ours it eventually collapsed. By contrast ours did the reverse, and it looks like it will expand forever. There is a neat symmetry. I guess you could make the case that it’s really just one universe, and the collapse and expansion mirror each other.

[nbulka]

We think the universe had to "begin" because we "began" and tend to anthropomorphize. Is that necessarily true? The universe is under no obligation to have a beginning. Sail around the Earth and you might just end up right where you started.

[yencabulator]

Current observations make it likely that our observable universe expands (think "stretches"), and the expansion will continue forever.

If it's expanding, then it was smaller earlier. Asking about the far past is a natural reaction, and the Big Bang theory is a pretty good attempt at explaining that.

https://en.wikipedia.org/wiki/Expansion_of_the_universe

https://en.wikipedia.org/wiki/Chronology_of_the_universe

[mc32]

The Sun had to begin. At one point it was just accreting gasses, then at some point gained enough mass to ignite. People also start at some point they begin as a daughter and grow eventually into a viable life. But also our galaxies had to form before our sun. So, yes there are beginnings to things. At one point they weren’t, at another point they were.

[jungturk]

Yes, but earth still had a beginning.

I agree with you, though - causal explanations are compelling and confer a sense of certainty and humans seem to like that, but it doesn't make them necessary.

[jama211]

Your first statement right off the bat is a bit of an assumption, why can’t the parent universe also have been formed inside a black hole? Why did you assume that?

[bagacrap]

Wouldn't every theory/model of the universe leave room for follow up questions? Why is it problematic if it doesn't answer literally every conceivable quandary?

[bhk]

It's black holes all the way down!