Hacker News Reader

Comment by kataklasm | Hacker News Reader

To expand on this, as stated in your source:

> [270B solar masses] is the maximum mass of a black hole that models predict, at least for luminous accreting SMBHs.

as well as:

> The limit is only 5×10^10 M [50B solar masses] for black holes with typical properties, but can reach 2.7×10^11 M [270B solar masses] at maximal prograde spin (a = 1).

However in the chapter before, it's stated:

> New discoveries suggest that many black holes, dubbed 'stupendously large', may exceed 100 billion or even 1 trillion M.

View on HN

There's a theory that the universe we live in is itself inside a giant black hole. No idea how it is supposed to have gotten so biig.

It couldn't have, the theory is nonsense.

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

I know this article. It's citing a bunch of speculative hypothesis by mostly this one person which relies on something super exotic called Einstein Cartan theory. I stand by my statement. I even suspect the article was written by them.

https://www.scientificamerican.com/article/do-we-live-inside...

I hate random links being thrown at me, because I don't know what you are trying to tell me. Perhaps you can spare a few key strokes.

For everyone else reading the thread, let me summarize. The article agrees with me:

> the entire observable universe exists within a black hole—except, that is, for all the evidence to the contrary

>....

> It does not seem likely that we live inside a rotating universe, let alone a black hole.

You have elsewhere in this thread objected to people providing links without giving context, so I hope you won't mind being asked to unpack this claim a little. Why is it nonsense? If, as you say, it's principally pushed by one person, who is that, and why does that argue against it?

(I'm not thinking this is too much to ask; saying it's wrong might require empirical support, but the claim that it's "nonsense" should be easier to justify.)

First of all, black holes have an interior and an exterior. Our universe only has an interior. Next, black holes have a singularity into which everything vanishes, or at least moves towards. Im our universe, everything moves away from a singularity. So if anything, it resembles a white hole more than a black hole. Also, our universe is expanding, whereas black holes shrink (unless matter falls into them, which can't happen to our universe because it has no exterior).

It really looks nothing like a black hole.

Agreed, how do you feel about our universe being some sort of post evaporated BH-like-thing from a previous universe-like-thing?

>Next, black holes have a singularity into which everything vanishes, or at least moves towards

I mean, everything in our universe does move towards something. The future.

The interior and exterior are isolated; we have no idea if are universe has an exterior or not and, according to present theory, never will.

As another comment pointed out, in GR our "future" is a singularity which everything moves towards (so what we see as a time dimension).

"Expanding" and "contracting" depend on your coordinate system. If your rulers are shrinking, you can't tell this from space expanding.

The common factor here is you are wanting to use our reference frame (somewhere in this universe, not near a black hole) to describe things as they would be seen from other reference frames.

> giant

How would we know the size? Relative to what?

If you assume constant density, anything becomes a black hole at certain volume. The question is: is our universe big enough to be a black hole or not.

Reply on news.ycombinator.com