How plausible is my pet theory that our universe is inside a black hole?

I’m no scientist. I have done no special research.

But I have a pet theory (I might have read it somewhere) that our universe exists inside a black hole. It answers the questions of “what came before the Big Bang?” (the collapse of a star) and “what exists outside our universe?” (another universe). And it would seem to account for why all of the elements for life derive from stars (the ole’ idea that “we are stardust”).

And, it offers the tantalizing prospect of answering what it’s like inside the black holes we see in our own universe. Yes, it’s black holes all the way down (and fits with my other non-scientific science theory that the universe is teeming with life, although it is so damn big - or we are so damn small - that we have simply never encountered it. We’re the proverbial ant hill in an abandoned parking lot wondering if there are other ants across the street in the grassy park - dude, ants are everywhere, but how can an ant even begin to conceive of all of those other habitats?)

While I enjoy my theory - what’s wrong with it? Why is it eye-rollingly bad? What fundamentals am I missing?

Please debunk this theory.

I’m no scientists myself, so I’m sure someone more knowledgeable will have a better critique of your theory.

Something I see wrong with your theory is that our universe is expanding. If we were “inside” a hole, then it should appear to us the universe is contracting. And we still haven’t addressed: Where did the universe come from that made the star that eventually died and became a black hole that somehow created this universe?

Your theory appears to be using circular logic.

You may be interested in Lee Smolin’s The Life of the Cosmos, in which he proposes the idea that the creation of a black hole produces a new universe, with fundamental constants slightly different than in its parent universe. This leads to a kind of cosmological natural selection, where the universes whose constants produce the most stars (and thus the most black holes) produce the most child universes. This explains why the constants in our universe seem specially tuned to produce matter.

I think there’s a basic question the OP needs to answer.

How does being in a universe-sized black hole differ from being in a universe-sized non-black hole?

If all you’ve done is slap on a science-y sounding term, you’ve done nothing.

What does “inside a black hole” even mean? There is space between the event horizon and the singularity, but we obviously aren’t in that space. If we were, gravity would be so strong that light cannot travel away from the singularity.

Chronos will probably soon be here to set me straight on this, but I believe I’ve read somewhere there is a slight possibility that we’re inside a black hole even smaller than the universe; although this would more or less require the hand of God to accomplish!

If we lived in a universe that was destined to contract into a Big Crunch at the end, then it would be true that our entire universe would be a black hole. Gravity would be so strong that nothing, not even light, could escape the inevitable contraction of everything back into a cosmic egg.

However, it doesn’t seem as if we live in a universe that will have a Big Crunch, and so our entire universe probably isn’t a black hole.

It’s another thing to consider if the entire universe is the opposite of a black hole, a white hole.–present_-_Big_Bang_as_Supermassive_White_Hole.

What I am envisioning is that we, from the inside, perceive our universe expanding, but that there is a divide between the limits of that expansion and the outside universe within which it’s expanding. Basically, we’re inside the balloon watching it expand, but someone outside the balloon would see that expansion is limited to the capacity of the balloon.

Now, I’m going to guess that you are going to note that black holes that we observe are not expanding. I’m postulating a counterintuitive idea that they are expanding (from the perspective of within) while being simultaneously restricted in their expansion by the confines of the black hole (from the perspective of the outside).

I’m not proposing a theory of how all of existence came to be…just our little universe.

I’m proposing the counterintuitive notion that, while a black hole looks to be a small point from the outside, it is actually as big as a universe if you are within it.

I’m saying that the event horizon is the outer edge of a universe, from which light (and all other things) can never escape. The singularity, defined as an infinitely small space where density and matter become infinite, is actually just the viewpoint of a universe from the outside. If you were within the singularity (as we all are, given that we are within our own universe), that “infinitely small space” is actually the “infinitely large universe” where all density and matter exist.

Again, I’m likely wrong. But it’s a conceptual idea that says, simply, that there are entire universes inside black holes, which appear to us as singularities.


From the observers point of view there is no difference. The composition of this universe is such that we are able to evolve and percive it. That energy/matter are somehow expelled to make another universe may be impossible to refute because there seems to be no way to get information once the material being observed crosses singularity.

This does not mean speculation about the OP idea is not interesting. I for one, having only a laypersons understanding of astrophysics, found the idea fascinating.

Since energy and matter cannot be destroyed, it makes sense that this energy and matter appears somewhere else. When I first heard of quasars I thought they were perhaps the other end of a black hole. The energy/matter has to go somewhere, so why not the other “end” of s black hole

An actual astrophysicist willing to take the time to crush our notions would be welcome ������

“Inside a singularity” is a contradiction in terms, isn’t it?

Also …

There’s a simple relationship between the mass of a black hole and it’s size (and therefore it’s density). Years ago I’d sometimes come across a back-of-the envelope calculation as to what the density of an observable universe-sized black hole would be and it turned out to be surprisingly similar to the density of our Universe.

Then dark matter turned up. Throw in the increase in the rate of expansion of the Universe (probably no Big Crunch) and all that gets thrown out.

To be taken seriously, you need to address a couple of questions:
What observed phenomena does your theory predict, that aren’t explained by theories that don’t include a black hole that surrounds us?

What possible observations would falsify your theory?

Just as the nature of space-time inside a black hole requires everything to fall towards its center, the nature of space-time in our universe requires everything to fall forward in time. And just as it’s impossible to escape from inside the event horizon of a black hole, it’s impossible to escape the universe to before the Big Bang.

Very recently Roger Penrose claims evidence in a preprint for a hypothesis seemingly more far-fetched than OP’s.

I hope this question isn’t directed at me! :slight_smile: I’d have to take the side of Sam the Piano Player:

The singularity is a viewpoint? We’re crushed inside an “infinitely small point” and that magically allows us to … something? Infinitely small becomes infinitely large? Whoa. Heavy, man.

That black holes may seed other universes is conjecture but hugely more plausible than we’re seeing the universe from inside of a singularity. Nor are the two hypotheses remotely similar or interchangeable. We’re not talking about seeding other universes here. That’s a different discussion.

:dubious: Why would our universe be special?

It’s certainly an idea that’s been floated every now and again, and it’s not obviously wrong. There are solutions—some of them in generalizations of Einstein gravity, such as the Einstein-Cartan theory—which look like a black hole from the outside, and like a universe from the inside. Here’s an article which discusses this sort of scenario—the reference to ‘spin’ here is not necessarily the quantum mechanical notion (although some have suggested a connection), but a property of the generalized theory of gravity that is employed, torsion, which is assumed to vanish in general relativity.

A few quick thoughts:

This puts me in mind of the idea that each sub-atomic particle could contain its own universe. An intriguing thought but ultimately a little meaningless. If it was the case is there any way we could possibly find out? What testable predictions do these hypothesis make?

It’s very unlikely that your hypothesis is true simply because there are a huge number of possible (yet largely un-testable) ideas like this. It would be really weird if, say, every black hole *and *every electron contained its own universe. Not to mention, what would a black hole or electron look like in these child universes? Is it universes all the way down?

There is absolutely nothing wrong with speculating along these lines, it can be entertaining and spark interesting conversations or even genuine science. It’s when people get overly attached to their pet theories that things go a bitpear-shaped.

I don’t understand why you think your ideas helps with this, can you explain please? Also, nucleosynthesis is well understood, both from atomic theory and astronomical observations. The final piece of the puzzle, where some elements like gold and iodine are formed, was finally solved in 2017. We have a good (although not perfect) understanding of where all the elements come from and can trace this evolution over the history of the universe.

20 years ago or so, your idea was extremely plausible, and in fact was one of the three main competing models for the Universe. As Lemur866 says, a Big Crunch universe is, in every way that matters, the same thing as a black hole. But it wouldn’t have been a black hole resulting from the collapse of a single star; it would have been a black hole resulting from the collapse of everything.

But then dark energy was discovered, which throws a real monkey wrench into everything.

I don’t understand your question. Where did I say our universe is special?