# A Black Hole in the Universal Neighborhood. **URL:** \ **Category:** Factual Questions\ **Created:** [October 8, 2001, 3:56pm UTC](https://boards.straightdope.com/t/a-black-hole-in-the-universal-neighborhood/86137 "2001-10-08T15:56:38Z")\ **Posts on this page:** 20\ **Page:** 1
**Author:** ![Phlosphr](https://avatars.discourse-cdn.com/v4/letter/p/c68b51/32.png) [@Phlosphr](https://boards.straightdope.com/u/Phlosphr)\ **Post date:** [October 8, 2001, 3:56pm UTC](https://boards.straightdope.com/t/a-black-hole-in-the-universal-neighborhood/86137/1 "2001-10-08T15:56:38Z")
OK Black Holes are one of only a fairly small number of cases in the history of science in which a theory was developed in great detail as a mathematical model before there was any evidence from observations that it was correct. Obviously today we have visual evidence they exist, and we have formed models of the way they apparently work. Granted to see a black hole, one must start ripping a star apart and start gobbling up galactic debris. My question is this: Can one think of a black hole with an opening at one end and a ‘path’ going through it…leading…Where??? Where do black holes dump the particle matter they suck up with their monster gravities. DO people know? What are some of the leading theories? \*I was watching a TLC programme called Hyperspace, with Sam Neil. WOW, that was wondrous. Of course it got me thinking and asking questions. And I needed to get away for a couple hours of thinking about ‘the’ terror in the world…So lets talk about space… ---
**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:** [October 8, 2001, 4:03pm UTC](https://boards.straightdope.com/t/a-black-hole-in-the-universal-neighborhood/86137/2 "2001-10-08T16:03:12Z")
> [@](#): > > \*Originally posted by Phlosphr \* > **Can one think of a black hole with an opening at one end and a ‘path’ going through it…leading…Where??? Where do black holes dump the particle matter they suck up with their monster gravities. DO people know? What are some of the leading theories?** A black hole gobbling up nearby matter doesn’t dump the matter anywhere. All the matter it gobbles up stays in the black hole, increasing its mass. By definition _nothing_ can escape a black hole. Basically the matter it eats gets smashed into the singularity…an infinitiely dense ‘spot’ at the center of the black hole that is also infinitely small (or does it have to abide by the Planck Length?..either way it is VERY small). Some sci-fi has suggested that a black hole might constitute a path to other places but I think most people accept the fact that a trip into a black hole is one way. ---
**Author:** ![warmgun](https://avatars.discourse-cdn.com/v4/letter/w/ecccb3/32.png) [@warmgun](https://boards.straightdope.com/u/warmgun)\ **Post date:** [October 8, 2001, 6:22pm UTC](https://boards.straightdope.com/t/a-black-hole-in-the-universal-neighborhood/86137/3 "2001-10-08T18:22:34Z")
I saw that same program. Amazing. What I can’t understand, given that a passing black hole can _drag the sun along with it_, is why something this big (dense?) doesn’t continue to grow expotentially sucking up matter from farther and farther away until one super-black hole gobbles up everything. ---
**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:** [October 8, 2001, 6:32pm UTC](https://boards.straightdope.com/t/a-black-hole-in-the-universal-neighborhood/86137/4 "2001-10-08T18:32:31Z")
> [@](#): > > \*Originally posted by warmgun \* > \*\*What I can’t understand, given that a passing black hole can _drag the sun along with it_, is why something this big (dense?) doesn’t continue to grow expotentially sucking up matter from farther and farther away until one super-black hole gobbles up everything. \*\* If our sun instantly turned into a black hole the earth would continue to orbit the black hole just as it does our sun today. The mass is the same (ignoring for a moment any explosions that sheds material in ‘normal’ black hole formation). The earth would not be sucked in although I’ll grant we’d have plenty of other problems on our hands should such a thing occur (and yes, I realize that our sun is not of a proper size to be a candidate for a black hole…it’s just an example). Gravity strength diminishes as the inverse square of distance. Double the distance from an object and the gravitational pull decreases to 1/4 of what it was. Double the distance again and its 1/16 and so on. In short, a black hole isn’t some universe gobbling monster. It’ll snatch whatever is in the immediate vicinity but most stars and planets are easily far enough away to maintain their own cohesion…that is, their own gravity can hold them together much easier than a distant black hole can pull them apart or suck them in. ---
**Author:** ![warmgun](https://avatars.discourse-cdn.com/v4/letter/w/ecccb3/32.png) [@warmgun](https://boards.straightdope.com/u/warmgun)\ **Post date:** [October 8, 2001, 8:55pm UTC](https://boards.straightdope.com/t/a-black-hole-in-the-universal-neighborhood/86137/5 "2001-10-08T20:55:13Z")
So the mass aquired by a BH as it grew in density (by gobbling more stars) wouldn’t extend it’s ability to ‘warp’ space? In other words, does more mass = larger diameter event horizon? Or is there an inverse square sitiation working here as well? Also, do we know if they just keep growing ‘forever’, or do they fizzle (ala tornados) or explode (mini big bang? ---
**Author:** ![g8rguy](https://avatars.discourse-cdn.com/v4/letter/g/7cd45c/32.png) [@g8rguy](https://boards.straightdope.com/u/g8rguy)\ **Post date:** [October 8, 2001, 9:39pm UTC](https://boards.straightdope.com/t/a-black-hole-in-the-universal-neighborhood/86137/6 "2001-10-08T21:39:34Z")
**warmgun** , there is indeed a simple relation between mass and the size of the event horizon: r = 2_G_M/c[sup]2[/sup], (I believe I have all the G’s and c’s in the right powers and right places). A black hole theoretically should continue to grow; at the very least, they’re continually absorbing the cosmic microwave background radiation (a black hole also presumably loses energy via Hawking radiation, but most black holes grow faster from CMBR than they lose from HR). ---
**Author:** ![deltopia](https://avatars.discourse-cdn.com/v4/letter/d/c6cbf5/32.png) [@deltopia](https://boards.straightdope.com/u/deltopia)\ **Post date:** [October 8, 2001, 9:40pm UTC](https://boards.straightdope.com/t/a-black-hole-in-the-universal-neighborhood/86137/7 "2001-10-08T21:40:16Z")
Sez here in my handy-dandy copy of “The Straight Dope: A Compendium of Human Knowledge”: > [@](#): > > …for reasons that I confess are not entirely clear to me, when a black hole grows to enormous mass, it becomes _less_ dense. If our entire galaxy collapsed into an ebony aperture (I am getting tired of typing black hole), said BH would be about ten billion light years across, with the average density of a thin gas. If we take this to its logical conclusion, it is possible that the known universe is _itself_ a black hole, with us living in it. Wherefore, it seems to me, the obvious question is: _how the hell do we get out of here?_ The casual attitude of our public officials toward this baleful possibility is nothing short of scandalous. _pp 201-202_ That seemed vaguely related to warmgun’s question, although it’s not a definitive answer by any stretch… ---
**Author:** ![barbitu8](https://avatars.discourse-cdn.com/v4/letter/b/839c29/32.png) [@barbitu8](https://boards.straightdope.com/u/barbitu8)\ **Post date:** [October 8, 2001, 9:40pm UTC](https://boards.straightdope.com/t/a-black-hole-in-the-universal-neighborhood/86137/8 "2001-10-08T21:40:43Z")
I think Whack-a-Mole answered your first question already. More mass means a larger event horizon and more warping of its neighborhood space. However, that doesn’t suck in astronomical bodies many miles away. If you happen to pass by, however, it could suck you in. Black holes can dissipate by evaporation, as Stephen Hawkings has explained. This is possible because of virtual particle pairs. There was a similar thread not too long ago on this. ---
**Author:** ![darkcool](https://avatars.discourse-cdn.com/v4/letter/d/5f8ce5/32.png) [@darkcool](https://boards.straightdope.com/u/darkcool)\ **Post date:** [October 9, 2001, 1:49am UTC](https://boards.straightdope.com/t/a-black-hole-in-the-universal-neighborhood/86137/9 "2001-10-09T01:49:35Z")
> [@](#): > > _Originally posted by warmgun \* > \*\* What I can’t understand, …_\* The reason you can’t understand is that you are too stupid to understand. Do us a favor and stay out of topics that are over your head. ---
**Author:** ![Squink](https://avatars.discourse-cdn.com/v4/letter/s/b5e925/32.png) [@Squink](https://boards.straightdope.com/u/Squink)\ **Post date:** [October 9, 2001, 2:49am UTC](https://boards.straightdope.com/t/a-black-hole-in-the-universal-neighborhood/86137/10 "2001-10-09T02:49:44Z")
> [@](#): > > _Originally posted by g8rguy \* > there is indeed a simple relation between mass and the size of the event horizon: r = 2_G\*M/c[sup]2[/sup]. That contrasts nicely with the formula for the radius of spherical bits of matter in euclidean (flat) space. The volume of a sphere = 4/3[sym]p[/sym]r[sup]3[/sup]. Setting density to 1 so that volume equals mass, and consolidating the constants: r = 0.23873 m[sup]1/3[/sup] ---
**Author:** ![John\_Kentzel-Griffin](https://avatars.discourse-cdn.com/v4/letter/j/ccd318/32.png) [@John\_Kentzel-Griffin](https://boards.straightdope.com/u/John_Kentzel-Griffin)\ **Post date:** [October 9, 2001, 3:23am UTC](https://boards.straightdope.com/t/a-black-hole-in-the-universal-neighborhood/86137/11 "2001-10-09T03:23:18Z")
> [@](#): > > \*Originally posted by \*\*\*darkcool \*\* > > > [@](#): > > > > _Originally posted by warmgun \* > > \*\* What I can’t understand, …_\* > > The reason you can’t understand is that you are too stupid to understand. Do us a favor and stay out of topics that are over your head. You’ve contributed nothing to the topic and you just buzz by for a personal attack. No, you don’t. We don’t allow personal attacks here. Lay off. NOW! Don’t do this again. **DrMatrix** - General Questions Moderator ---
**Author:** ![Nen](https://avatars.discourse-cdn.com/v4/letter/n/c5a1d2/32.png) [@Nen](https://boards.straightdope.com/u/Nen)\ **Post date:** [October 9, 2001, 3:45am UTC](https://boards.straightdope.com/t/a-black-hole-in-the-universal-neighborhood/86137/12 "2001-10-09T03:45:53Z")
> [@](#): > > \*Originally posted by Phlosphr \* > Can one think of a black hole with an opening at one end and a ‘path’ going through it…leading…Where??? Where do black holes dump the particle matter they suck up with their monster gravities. DO people know? What are some of the leading theories? There are two theories as to where the matter ends up. The leading theory is that it doesn’t go anywhere, i.e., it arrives at the singularity and that’s it. Another theory is a kind of combination with wormhole theory insofar as it is postulated that the matter is the output of a quasar. There isn’t much evidence to back this assertion. Just to clarify, black hole theory isn’t a rarity in terms of postulation preceding observation. ---
**Author:** ![warmgun](https://avatars.discourse-cdn.com/v4/letter/w/ecccb3/32.png) [@warmgun](https://boards.straightdope.com/u/warmgun)\ **Post date:** [October 9, 2001, 3:53am UTC](https://boards.straightdope.com/t/a-black-hole-in-the-universal-neighborhood/86137/13 "2001-10-09T03:53:21Z")
> [@](#): > > \*Originally posted by barbitu8 \* > \*\*Black holes can dissipate by evaporation, as Stephen Hawkings has explained. This is possible because of virtual particle pairs. There was a similar thread not too long ago on this. \*\* Thanks, I think I found it. Do you mean [this](http://boards.straightdope.com/sdmb/showthread.php?postid=1592714#post1592714) thread/post? ---
**Author:** ![erislover](https://avatars.discourse-cdn.com/v4/letter/e/71e660/32.png) [@erislover](https://boards.straightdope.com/u/erislover)\ **Post date:** [October 9, 2001, 4:45am UTC](https://boards.straightdope.com/t/a-black-hole-in-the-universal-neighborhood/86137/14 "2001-10-09T04:45:38Z")
Though I don’t have any equations handy, black hole radiation is inversely proportional to its mass. So long as it started out big enough, it would continue to grow, Hawking radiation or no. ---
**Author:** ![barbitu8](https://avatars.discourse-cdn.com/v4/letter/b/839c29/32.png) [@barbitu8](https://boards.straightdope.com/u/barbitu8)\ **Post date:** [October 9, 2001, 8:01pm UTC](https://boards.straightdope.com/t/a-black-hole-in-the-universal-neighborhood/86137/15 "2001-10-09T20:01:22Z")
> [@](#): > > \*Originally posted by warmgun \* > \*\* > > > [@](#): > > > > \*Originally posted by barbitu8 \* > > \*\*Black holes can dissipate by evaporation, as Stephen Hawkings has explained. This is possible because of virtual particle pairs. There was a similar thread not too long ago on this. \*\* > > Thanks, I think I found it. Do you mean [this](http://boards.straightdope.com/sdmb/showthread.php?postid=1592714#post1592714) thread/post? \*\* Congrats! You found it. Obviously a black hole of any size is not going away right away, but Hawkings said that there have been gadzillions of tiny little black holes that dissipate almost immediately. ---
**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:** [October 9, 2001, 9:28pm UTC](https://boards.straightdope.com/t/a-black-hole-in-the-universal-neighborhood/86137/16 "2001-10-09T21:28:53Z")
> [@](#): > > \*Originally posted by deltopia \* > Sez here in my handy-dandy copy of “The Straight Dope: A Compendium of Human Knowledge”: > > > [@](#): > > > > …for reasons that I confess are not entirely clear to me, when a black hole grows to enormous mass, it becomes _less_ dense. **If our entire galaxy collapsed into an ebony aperture (I am getting tired of typing black hole), said BH would be about ten billion light years across**, with the average density of a thin gas. If we take this to its logical conclusion, it is possible that the known universe is _itself_ a black hole, with us living in it. Wherefore, it seems to me, the obvious question is: _how the hell do we get out of here?_ The casual attitude of our public officials toward this baleful possibility is nothing short of scandalous. _pp 201-202_ [Highlighting Mine] Can someone explain this to me? Ten _billion_ light years across? First off…I would think 10 billion light years would be nearly the size of the universe (depending on what figure you care to use for the age of the universe which I have heard as anywhere from 10-15 billion years old). That seems ludicrously large. Second, the Milky Way Galaxy is currently about 100,000 light years across. If you smush all the stars in the Milky Way together I would expect a slightly smaller or the same diameter to the current 100,000 light years. I thought for the purposes of calculating the gravitational effect on other galaxies you can consider the Milky Way as a point source and not all spread out. Given that replacing the Miky Way with a black hole of the smae mass should be unnoticeable to other galaxies (gravitationally speaking). Even if I assume a typo in the earlier post and replace billion with million I think it is still too large. Any one know for certain? It worries me a bit to querstion the master but I think we (or at least I) am missing something here. ---
**Author:** ![kanicbird](https://avatars.discourse-cdn.com/v4/letter/k/5f8ce5/32.png) [@kanicbird](https://boards.straightdope.com/u/kanicbird)\ **Post date:** [October 9, 2001, 9:34pm UTC](https://boards.straightdope.com/t/a-black-hole-in-the-universal-neighborhood/86137/17 "2001-10-09T21:34:22Z")
> [@](#): > > . Another theory is a kind of combination with wormhole theory insofar as it is postulated that the matter is the output of a quasar That is the white hole theory. Each blackhole basically burrows a tunnel in spacetime and any matter that goes in to the black hole is expelled through the white hole. Mathmatically sound few think they are real possibilities. a wormhole would also be a ‘tunnel’ in spacetime but not nearly as violent - or so I hear. ---
**Author:** ![Sea\_Sorbust](https://avatars.discourse-cdn.com/v4/letter/s/6f9a4e/32.png) [@Sea\_Sorbust](https://boards.straightdope.com/u/Sea_Sorbust)\ **Post date:** [October 9, 2001, 9:50pm UTC](https://boards.straightdope.com/t/a-black-hole-in-the-universal-neighborhood/86137/18 "2001-10-09T21:50:29Z")
“Ten billion light years across?” Perhaps it should have been “miles” or “kms”; perhaps, a slip of the [mental] pen. :o Does the physics have anything to say about a black hole getting _too_ big? Big enough, that is, to change the very nature of space? ---
**Author:** ![Waverly](https://avatars.discourse-cdn.com/v4/letter/w/57b2e6/32.png) [@Waverly](https://boards.straightdope.com/u/Waverly)\ **Post date:** [October 9, 2001, 9:58pm UTC](https://boards.straightdope.com/t/a-black-hole-in-the-universal-neighborhood/86137/19 "2001-10-09T21:58:17Z")
> [@](#): > > \*Originally posted by Phlosphr \* > Where do black holes dump the particle matter they suck up with their monster gravities. DO people know? What are some of the leading theories It is not the only theory, but I personally find it most plausible: A quirk of relativity is that time dilates as gravity increases. As material crosses the event horizon and begins its journey to the center of the black hole, it becomes incredibly dense while time simultaneously slows from the perspective of the matter. This theory suggests that matter never completes the journey, time continually slowing, never allowing it to reach the center. [yeah, I have a cite, but it’s at home. I can supply it later if anyone is interested.] ---
**Author:** ![Sea\_Sorbust](https://avatars.discourse-cdn.com/v4/letter/s/6f9a4e/32.png) [@Sea\_Sorbust](https://boards.straightdope.com/u/Sea_Sorbust)\ **Post date:** [October 9, 2001, 10:09pm UTC](https://boards.straightdope.com/t/a-black-hole-in-the-universal-neighborhood/86137/20 "2001-10-09T22:09:21Z")
> [@](#): > > _Originally posted by **Waverly:** _ > A quirk of relativity is that time dilates as gravity increases. If that is true, then shouldn’t it also be true (by the same set of equations) that the velocity will increase as gravity increases? (I am fully prepared to be given the **darkcool** treatment; that is, to be told that I know nothing.) [Next page](https://boards.straightdope.com/t/a-black-hole-in-the-universal-neighborhood/86137.md?page=2)