# Yet another black hole question

**URL:** <https://boards.straightdope.com/t/yet-another-black-hole-question/1010627>\
**Category:** Factual Questions\
**Created:** [November 22, 2024, 10:21pm UTC](https://boards.straightdope.com/t/yet-another-black-hole-question/1010627 "2024-11-22T22:21:40Z")\
**Posts on this page:** 20\
**Page:** 1

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**Author:** ![Lumpy](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/lumpy/32/446_2.png) [@Lumpy](https://boards.straightdope.com/u/Lumpy)\
**Post date:** [November 22, 2024, 10:21pm UTC](https://boards.straightdope.com/t/yet-another-black-hole-question/1010627/1 "2024-11-22T22:21:40Z")

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Once something has fallen past a black hole’s event horizon, is it that nothing inside can get outside the horizon again, or is it that nothing can move away from the singularity even momentarily? I thought I had read remarks to the effect of the latter, but that seems problematic to me: it would mean that the forces holding an object together couldn’t propagate outwards and therefore the object would be immediately shredded in the direction of infall.

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**Author:** ![Whack-a-Mole](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/whack-a-mole/32/141_2.png) [@Whack-a-Mole](https://boards.straightdope.com/u/Whack-a-Mole)\
**Post date:** [November 22, 2024, 10:30pm UTC](https://boards.straightdope.com/t/yet-another-black-hole-question/1010627/2 "2024-11-22T22:30:39Z")

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IIRC it would be possible to move around inside the event horizon and even temporarily move away from the singularity. Consider something orbiting the singularity in an elliptical orbit. And, of course, it is not possible to escape to the outside of the event horizon. Once in, that’s the end of it. There is no leaving.

But, the singularity is _always_ in your future once inside the event horizon so, eventually, you and the singularity _will_ meet. So, it can’t be a stable orbit but neither is it necessarily a “straight” line to the singularity once inside the event horizon.

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**Author:** ![DPRK](https://avatars.discourse-cdn.com/v4/letter/d/4491bb/32.png) [@DPRK](https://boards.straightdope.com/u/DPRK)\
**Post date:** [November 22, 2024, 10:57pm UTC](https://boards.straightdope.com/t/yet-another-black-hole-question/1010627/3 "2024-11-22T22:57:05Z")

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> [@Whack-a-Mole](#):
>
> Consider something orbiting the singularity in an elliptical orbit.

Innermost stable orbit is _outside_ the event horizon

> **[Innermost stable circular orbit](https://en.wikipedia.org/wiki/Innermost_stable_circular_orbit)**
>
> The innermost stable circular orbit (often called the ISCO) is the smallest marginally stable circular orbit in which a test particle can stably orbit a massive object in general relativity. The location of the ISCO, the ISCO-radius (
>   
>     
>       
>         
> r
>           
>             
> i
> s
> c
> o
>             
>           
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> {\\displaystyle r\_{\\mathrm {isco} }}
>   
> ), depends on the mass and angular momentum (spin) Th...

> [@Whack-a-Mole](#):
>
> IIRC it would be possible to move around inside the event horizon

You might need to adjust your trajectory slightly  
[https://arxiv.org/pdf/0705.1029v2](https://arxiv.org/pdf/0705.1029v2)

but you would be screwed—can’t move away from the singularity even a little bit.

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**Author:** ![enipla](https://avatars.discourse-cdn.com/v4/letter/e/54ee81/32.png) [@enipla](https://boards.straightdope.com/u/enipla)\
**Post date:** [November 22, 2024, 11:40pm UTC](https://boards.straightdope.com/t/yet-another-black-hole-question/1010627/4 "2024-11-22T23:40:08Z")

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Ok, dumb question.

So the universe was created from the big bang. Ok…

Are these black holes sort of little universes unto themselves, that could also bang? I see a book here. Fiction.

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**Author:** ![Exapno\_Mapcase](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/exapno_mapcase/32/1051_2.png) [@Exapno\_Mapcase](https://boards.straightdope.com/u/Exapno_Mapcase)\
**Post date:** [November 23, 2024, 1:08am UTC](https://boards.straightdope.com/t/yet-another-black-hole-question/1010627/5 "2024-11-23T01:08:14Z")

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Nobody has a solid understanding of what caused our universe to come into being.

Black holes, however, are just collections of mass. The one at the center of our galaxy is about 4 million times the mass of our sun. That’s piddling compared with the size of the universe, which currently is estimated to contain 200,000 million million million stars. And all those combined have only 20% of the mass of dark matter. A huge energy discrepancy.

While there’s a lot we don’t know about the singularity inside a black hole - some even doubt that such a thing exists - universe creation is probably not likely a property.

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**Author:** ![Whack-a-Mole](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/whack-a-mole/32/141_2.png) [@Whack-a-Mole](https://boards.straightdope.com/u/Whack-a-Mole)\
**Post date:** [November 23, 2024, 1:15am UTC](https://boards.straightdope.com/t/yet-another-black-hole-question/1010627/6 "2024-11-23T01:15:30Z")

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\<\< deleted by poster…misread the post I was responding to \>\>

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**Author:** ![Der\_Trihs](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/der_trihs/32/233_2.png) [@Der\_Trihs](https://boards.straightdope.com/u/Der_Trihs)\
**Post date:** [November 23, 2024, 1:17am UTC](https://boards.straightdope.com/t/yet-another-black-hole-question/1010627/7 "2024-11-23T01:17:46Z")

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NM, mistake corrected.

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**Author:** ![Chronos](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/chronos/32/134_2.png) [@Chronos](https://boards.straightdope.com/u/Chronos)\
**Post date:** [November 23, 2024, 1:41am UTC](https://boards.straightdope.com/t/yet-another-black-hole-question/1010627/8 "2024-11-23T01:41:46Z")

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> [@enipla](#):
>
> Are these black holes sort of little universes unto themselves, that could also bang? I see a book here. Fiction.

They’re sort of little universes unto themselves, that already did bang.

To the original question, it’s no different from outside of a black hole. Forces can’t propagate backwards in time, but that doesn’t cause objects to fall apart, because forces don’t need to propagate backwards in time in order to hold objects together.

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**Author:** ![Darren\_Garrison](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/darren_garrison/32/92_2.png) [@Darren\_Garrison](https://boards.straightdope.com/u/Darren_Garrison)\
**Post date:** [November 23, 2024, 3:29am UTC](https://boards.straightdope.com/t/yet-another-black-hole-question/1010627/9 "2024-11-23T03:29:31Z")

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> [@enipla](#):
>
> Are these black holes sort of little universes unto themselves, that could also bang? I see a book here. Fiction.

I think many, many books have already been written with that idea. There is a related idea of Cosmological Natural Selection that suggests the evolutionary fitness of universes with the properties to allow for the production of black holes.

> **[Cosmological natural selection](https://en.wikipedia.org/wiki/Cosmological_natural_selection)**
>
> Cosmological natural selection, also called the fecund universes, is a hypothesis proposed by Lee Smolin intended as a scientific alternative to the anthropic principle. It addresses why our universe has the particular properties that allow for complexity and life. The hypothesis suggests that a process analogous to biological natural selection applies at the grandest of scales. Smolin first proposed the idea in 1992 and summarized it in a book aimed at a lay audience called The Life of the Cosm...

One book called _Learning the World_ by Ken MacLeod has a breif mention of the cosmogenic engines powering their starships:

> Sublime as the sight was, it took a knowledge of what it did to take the full measure of its magnificence. Like its polar counterpart in the rearward cone, the titanic engine was a cosmogonic machine. At its core was a process that – second by second when it powered the ship’s flight, hour by hour when, as now, it powered only the sunline – compacted the equivalent of a multi-megaton nuclear explosion into a space the size of a hydrogen atom. Its primary effect was to accelerate the reaction mass to relativistic velocities. As a side-effect, invisible but inevitable, it generated universes. From each compacted explosion, like a stray spark from a hammer, a new singularity exploded out of space-time and inflated in an instant to give birth to a new cosmos. Some inconceivably minute fraction of the energy of that inflation could be tapped to make the engine self-sustaining. Invented in the Moon Caves, the cosmogonic engine had given man the stars. At one level efficient beyond cavil, on another it was the most profligate of man’s devices: it blew multiple universes like bubbles, for the mere sake of moving mass, and at an average speed of 0.01c at that.

With the mention that this process produces universes with similar properties to the parent universe, thus favoring the creation not only of universes capable of producing black holes, but even favoring universes with properties favoring producing starships. (And that our universe is one moment of starship exhaust from a different universe.)

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**Author:** ![Whack-a-Mole](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/whack-a-mole/32/141_2.png) [@Whack-a-Mole](https://boards.straightdope.com/u/Whack-a-Mole)\
**Post date:** [November 23, 2024, 3:52am UTC](https://boards.straightdope.com/t/yet-another-black-hole-question/1010627/10 "2024-11-23T03:52:27Z")

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> [@Darren\_Garrison](#):
>
> With the mention that this process produces universes with similar properties to the parent universe, thus favoring the creation not only of universes capable of producing black holes, but even favoring universes with properties favoring producing starships.

I think we can think of a more simple solution, and we have. The [Anthropic principle](https://en.wikipedia.org/wiki/Anthropic_principle) covers it pretty well and is well established.

If you have infinite universes (or even just a large number of them) then some will be suitable for life and spaceships. We happen to live in one. Even if it is a super-remote chance it doesn’t really matter. We live in a rare universe that allows life to exist. It doesn’t matter how unlikely it is because it almost has to happen somewhere.

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**Author:** ![Darren\_Garrison](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/darren_garrison/32/92_2.png) [@Darren\_Garrison](https://boards.straightdope.com/u/Darren_Garrison)\
**Post date:** [November 23, 2024, 4:00am UTC](https://boards.straightdope.com/t/yet-another-black-hole-question/1010627/11 "2024-11-23T04:00:42Z")

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> [@Whack-a-Mole](#):
>
> I think we can think of a more simple solution, and we have. The [Anthropic principle](https://en.wikipedia.org/wiki/Anthropic_principle) covers it pretty well and is well established.

The very first sentence in my Wiki site, shown in the preview box:

“Cosmological natural selection, also called the fecund universes, is a hypothesis proposed by Lee Smolin intended as a scientific alternative to the anthropic principle.”

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**Author:** ![Whack-a-Mole](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/whack-a-mole/32/141_2.png) [@Whack-a-Mole](https://boards.straightdope.com/u/Whack-a-Mole)\
**Post date:** [November 23, 2024, 4:06am UTC](https://boards.straightdope.com/t/yet-another-black-hole-question/1010627/12 "2024-11-23T04:06:23Z")

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Apologies. I missed that.

Reading the Wiki you linked I am not persuaded.

I think [Occam’s Razor](https://en.wikipedia.org/wiki/Occam%27s_razor) is probably right and the simpler solution is we just have a lot of alternatives and some few are the right mix by chance to produce life and spaceships.

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**Author:** ![Darren\_Garrison](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/darren_garrison/32/92_2.png) [@Darren\_Garrison](https://boards.straightdope.com/u/Darren_Garrison)\
**Post date:** [November 23, 2024, 4:10am UTC](https://boards.straightdope.com/t/yet-another-black-hole-question/1010627/13 "2024-11-23T04:10:23Z")

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I didn’t post that link as an endorsement of it being the true state of the universe, just as an introduction to a concept from a work of fiction, as I was replying to “Are these black holes sort of little universes unto themselves, that could also bang? I see a book here. Fiction.”

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**Author:** ![Lumpy](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/lumpy/32/446_2.png) [@Lumpy](https://boards.straightdope.com/u/Lumpy)\
**Post date:** [November 23, 2024, 4:53am UTC](https://boards.straightdope.com/t/yet-another-black-hole-question/1010627/14 "2024-11-23T04:53:18Z")

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> [@DPRK](#):
>
> but you would be screwed—can’t move away from the singularity even a little bit.

That’s what I was asking: if this is so, it means there can’t be any causality within an object that has fallen into a black hole; it’s now been sliced into films of Planck-length thickness.

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**Author:** ![markn\_1](https://avatars.discourse-cdn.com/v4/letter/m/f9ae1b/32.png) [@markn\_1](https://boards.straightdope.com/u/markn_1)\
**Post date:** [November 23, 2024, 5:02am UTC](https://boards.straightdope.com/t/yet-another-black-hole-question/1010627/15 "2024-11-23T05:02:46Z")

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Smolin makes an interesting analogy to explain why he thinks cosmological natural selection is preferable to the anthropic principle.

Suppose one were to look at Earth’s biology and try to explain why so many species seem to be so perfectly fitted to the ecological niche they occupy. Why are finch’s beaks fitted to deal with the food they eat; why do stick insects mimic sticks so well; why do bird’s wings allow them to fly; why do giraffes have such long necks allowing them to reach their food; etc? Biological evolution is a robust explanation, and is analogous to cosmological natural selection in that it explains how things gradually evolve to the perfectly fitted situation we observe. On the other hand, the explanation that is analogous to the anthropic principle is: there are a whole bunch of worlds with random characteristics, and we just happen to live on one where all these organisms are perfectly fitted, but it’s all completely by chance. It’s not a very satisfying explanation.

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**Author:** ![Whack-a-Mole](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/whack-a-mole/32/141_2.png) [@Whack-a-Mole](https://boards.straightdope.com/u/Whack-a-Mole)\
**Post date:** [November 23, 2024, 5:04am UTC](https://boards.straightdope.com/t/yet-another-black-hole-question/1010627/16 "2024-11-23T05:04:26Z")

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> [@DPRK](#):
>
> …can’t move away from the singularity even a little bit.

Why not?

Are you saying anything that passes the event horizon is hoovered straight in to the singularity along the shortest path possible?

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**Author:** ![Whack-a-Mole](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/whack-a-mole/32/141_2.png) [@Whack-a-Mole](https://boards.straightdope.com/u/Whack-a-Mole)\
**Post date:** [November 23, 2024, 5:08am UTC](https://boards.straightdope.com/t/yet-another-black-hole-question/1010627/17 "2024-11-23T05:08:03Z")

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On earth evolution makes sense.

I do not see why whole universes would care to “evolve” one way or another. Indeed, they do not evolve. They have no preference. It is random chance. We live in a random chance that supports life.

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**Author:** ![Der\_Trihs](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/der_trihs/32/233_2.png) [@Der\_Trihs](https://boards.straightdope.com/u/Der_Trihs)\
**Post date:** [November 23, 2024, 5:13am UTC](https://boards.straightdope.com/t/yet-another-black-hole-question/1010627/18 "2024-11-23T05:13:04Z")

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> [@Whack-a-Mole](#):
>
> On earth evolution makes sense.
> 
> I do not see why whole universes would care to “evolve” one way or another.

_If_ universes spawn from older universes, _if_ they vary somewhat from their progenitor but aren’t outright random, _and_ if those variations cause them to reproduce more or less successfully then you have what’s needed for a form of natural selection. Of course those “ifs” are all speculative.

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**Author:** ![Whack-a-Mole](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/whack-a-mole/32/141_2.png) [@Whack-a-Mole](https://boards.straightdope.com/u/Whack-a-Mole)\
**Post date:** [November 23, 2024, 5:16am UTC](https://boards.straightdope.com/t/yet-another-black-hole-question/1010627/19 "2024-11-23T05:16:09Z")

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> [@Der\_Trihs](#):
>
> …_and_ if those variations cause them to reproduce more or less successfully…

That’s the thing.

Is there a selective advantage to a whole universe being capable of supporting life? Those universes that can support life are somehow more successful and then spawn new universes? (assuming one universe spawns another and passes on some aspect of itself…a whole other big question.)

Seems a big reach to me to make that case.

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**Author:** ![Der\_Trihs](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/der_trihs/32/233_2.png) [@Der\_Trihs](https://boards.straightdope.com/u/Der_Trihs)\
**Post date:** [November 23, 2024, 5:22am UTC](https://boards.straightdope.com/t/yet-another-black-hole-question/1010627/20 "2024-11-23T05:22:12Z")

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> [@Whack-a-Mole](#):
>
> Is there a selective advantage to a whole universe being capable of supporting life? Those universes that can support life are somehow more successful and then spawn new universes?

Nobody knows; however our universe seems oddly life-friendly and it’s the only example we have.

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