# Black Hole **URL:** \ **Category:** Factual Questions\ **Created:** [March 14, 2010, 7:34pm UTC](https://boards.straightdope.com/t/black-hole/532469 "2010-03-14T19:34:07Z")\ **Posts on this page:** 20\ **Page:** 2
**Author:** ![BigT](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/bigt/32/12044_2.png) [@BigT](https://boards.straightdope.com/u/BigT)\ **Post date:** [March 15, 2010, 4:33am UTC](https://boards.straightdope.com/t/black-hole/532469/21 "2010-03-15T04:33:04Z")
> [@AClockworkMelon](#): > > But I thought that simply becoming more dense, without necessarily increasing in surface area, would result in more mass. > 😕 Since a black hole’s volume is directly proportionate to its mass, the density is always constant. You can actually think of a black hole as already being infinitely dense. The only reason it has a size is because of its gravity. The actual singularity has no volume, just mass. It’s an infinitely small point. ---
**Author:** ![Yumblie](https://avatars.discourse-cdn.com/v4/letter/y/76d3ee/32.png) [@Yumblie](https://boards.straightdope.com/u/Yumblie)\ **Post date:** [March 15, 2010, 5:59am UTC](https://boards.straightdope.com/t/black-hole/532469/22 "2010-03-15T05:59:46Z")
> [@Whack-a-Mole](#): > > See this is where I part ways with physicists. Or rather where they lose me. > > I am nowhere near able to argue the math of it as you and some others here can but while it may make your calculations simpler it seems absurd to say the mass is not “anywhere”. > > I have done these threads long enough to know things like quantum effects can have disturbingly un-intuitive results. Nevertheless the black holes are there. They have mass which we can measure. That being the case how can you say the mass is “nowhere”? Clearly it is at the center of the BH as evidenced by the orbits of things around it. > > Perhaps a zero-dimensional point cannot be said to be anywhere…that is beyond me. Still, the things exist, mass is not siphoned to another universe (as far as we know) or otherwise destroyed (thought that was not possible…you can mutate matter but in the end it can all be accounted for) so the black holes are “there”. So how can a physicist keep a straight face and say the matter is nowhere? Using singularities is actually pretty common in freshman physics problems, though it’s just glossed over. Take the simplest gravity problem, finding the field around a planet A. Planet A is said to have mass M, so it creates a gravitational field around it. But in the simplest case, Planet A is considered a point mass, where all the mass is concentrated at a point of zero size. Since it has zero size, none of the space in this problem is taken up by this object. So in a sense, the mass doesn’t “exist”, though the gravitational force emanating from it does, and that’s what’s important. If you instead wanted to treat it like a real planet and give it some size, you’d have tidal forces and it’d be a more complicated problem. The nice thing is that as long as you’re far enough away from a planet, you can pretend it doesn’t exist and that the gravitational field is emanating from a single point, and the calculations will work out fine. It’s the same thing in general relativity, except instead of a gravitational field, you have curvature of spacetime. For a simple schwarzchild black hole, curvature accelerates objects toward a certain point, which we call the center of the black hole. Since it’s a point source of zero size, it doesn’t really exist in a traditional sense, but the curvature around it does. What’s strange is that, as far current physics tells us, after something collapses into a black hole there’s nothing able to stop it from collapsing any further, so its size gets smaller and smaller until it hits 0. It actually becomes the simplified zero-size point mass of freshman physics problems. It’s likely that quantum gravity will fix this somehow, but for now, all we can do is treat the center of a black hole like a real live singularity. Also, the whole non-existent thing is carried further by the fact that anything beyond the event horizon cannot possibly interact with the rest of the universe, so for all intents and purposes it doesn’t exist anymore. The curvature outside the horizon certainly exists, and we can tell ourselves that it’s being created by something inside it, but for practical purposes what’s actually inside the event horizon doesn’t matter. It’s all in how you look at it, and how you answer the question that if something occupies _zero space_, does it actually exist? ---
**Author:** ![AClockworkMelon](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/aclockworkmelon/32/10803_2.png) [@AClockworkMelon](https://boards.straightdope.com/u/AClockworkMelon)\ **Post date:** [March 15, 2010, 6:44am UTC](https://boards.straightdope.com/t/black-hole/532469/23 "2010-03-15T06:44:52Z")
> [@BigT](#): > > Since a black hole’s volume is directly proportionate to its mass, the density is always constant. > > You can actually think of a black hole as already being infinitely dense. The only reason it has a size is because of its gravity. The actual singularity has no volume, just mass. It’s an infinitely small point. OK, this is what I was looking for. So when people refer to the “size” of a black hole, they’re actually referring to the area of its event horizon? ---
**Author:** ![Punoqllads](https://avatars.discourse-cdn.com/v4/letter/p/d2c977/32.png) [@Punoqllads](https://boards.straightdope.com/u/Punoqllads)\ **Post date:** [March 15, 2010, 7:32am UTC](https://boards.straightdope.com/t/black-hole/532469/24 "2010-03-15T07:32:58Z")
> [@BigT](#): > > Since a black hole’s volume is directly proportionate to its mass, the density is always constant. A black hole’s _radius_ is directly proportional to its mass. Volume = 4/3 pi r[sup]3[/sup]. If the mass of a black hole doubles, its volume becomes 8 times as large, reducing its density by a factor of 4. ---
**Author:** ![Anne\_Neville](https://avatars.discourse-cdn.com/v4/letter/a/b9e5f3/32.png) [@Anne\_Neville](https://boards.straightdope.com/u/Anne_Neville)\ **Post date:** [March 15, 2010, 2:26pm UTC](https://boards.straightdope.com/t/black-hole/532469/25 "2010-03-15T14:26:51Z")
> [@AClockworkMelon](#): > > So when people refer to the “size” of a black hole, they’re actually referring to the area of its event horizon? Yes, when they refer to the radius of a black hole. The other common way to refer to the size of a black hole is by its mass. > [@Jake](#): > > Seems that while they’re toolin’ around the Universe they could eventually swallow up each other, then vacuum up the stars and stuff like that there ? Black holes don’t vacuum stuff up. The only force pulling anything into a black hole is gravity. There’s no other mysterious suction force. Stuff falls into a black hole and can’t get out. A black hole could swallow a star, but the star would have to collide with the black hole for that to happen. Stellar collisions are rare in our part of the galaxy. Think about it- the nearest star to the Sun is Proxima Centauri, 4.3 light-years away. The radius of the Sun is about 9 light-_seconds_. That means that light takes 9 seconds to cross the Sun, and 4.3 years to go from the Sun to the nearest star. Stars are tiny in relation to the distance between them. If you had one tennis ball in Philadelphia, and another one in Indianapolis, that would be an approximately proportionate model, in distance and size, between the Sun and Proxima Centauri. Stars are just _not_ going to collide when they’re that far apart. Since the only way a black hole can swallow up a star is for the black hole and the star to collide, that isn’t going to happen in our part of the galaxy either. The black holes in this part of the galaxy are fairly small, too. Supermassive black holes, the ones that can be the size of the solar system, are only found in the centers of galaxies. The black holes in this part of the galaxy come from supernovae, and are smaller (in radius, not less massive) than the Sun. We’re no more likely (probably much less likely) to collide with a stellar-mass black hole than we are to collide with another star. The center of the galaxy is another story, but we’re not there, and we’re not going there any time soon. Even if the Sun were headed into the center of the galaxy at the speed of light (which it isn’t), it would take us about 25,000 years to get there. For comparison, we have recorded history back to about 4500 BC, which is only 6500 years. It would take more than three times as long as all of recorded history for the Sun to get to the center of the galaxy if it were traveling straight there at the speed of light. The Sun isn’t moving toward the center of the galaxy anywhere near that fast. ---
**Author:** ![Tom\_Tildrum](https://avatars.discourse-cdn.com/v4/letter/t/e95f7d/32.png) [@Tom\_Tildrum](https://boards.straightdope.com/u/Tom_Tildrum)\ **Post date:** [March 15, 2010, 3:11pm UTC](https://boards.straightdope.com/t/black-hole/532469/26 "2010-03-15T15:11:36Z")
> [@Chronos](#): > > The reason we say that there is no matter in a black hole is that the simplest form of the black hole equations has nothing but pure vacuum everywhere. You could say that all of the mass is in the singularity, but what makes the singularity a singularity is that it’s not an “anywhere”: It’s not that there’s something weird at that location, it’s that that location just doesn’t exist. Now, of course, it’s possible that the simplest model is incorrect. It may be that once we understand quantum gravity, we’ll realize that there isn’t a singularity after all, but that there really is some extremely exotic form of matter in a tiny lump at the center. How big that lump would be is anyone’s guess, since we can only speculate about its very existence, but the Planck length is as reasonable a guess as any. I thought that rotating black holes were predicted to have a ring-shaped singularity (and that most black holes would be rotating). Is that outdated? If we can predict that it is a ring, then can we predict its radius? And doesn’t that mean that there is some “there” there? ---
**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:** [March 15, 2010, 4:14pm UTC](https://boards.straightdope.com/t/black-hole/532469/27 "2010-03-15T16:14:32Z")
> [@AClockworkMelon](#): > > We can’t actually see black holes, because light can’t escape from them, correct? So we can only examine them by examining the gravitational affect they have on nearby celestial bodies. Black holes that are at the centers of galaxies have large amounts of matter surrounding them and responding to the powerful gravitational pull. That creates all sorts of spectacular effects visible in various wavelengths. And that’s how most black holes are spotted. > **[Astronomers Untangle Black Hole Radiation](https://www.space.com/513-astronomers-untangle-black-hole-radiation.html)** > > Two Italian researchers pored through a series of black hole observations taken over about five years to separate its X-ray emissions into those belched by powerful polar jets and those originating from a disk of material swirling around the object’s... > [@](#): > > Although astronomers have never seen a black hole directly, they can infer their presence by gravitational effects on nearby stars and the radiation oozing from a disk of material that feeds the object. Supermassive black holes, which theorists say could sit at the center of some galaxies and hold more than a billion Suns of material, can also fire off powerful jets from their rotational poles, beaming X-rays, radio waves and other radiation into space. [http://www.washingtonpost.com/wp-dyn/content/article/2007/12/17/AR2007121701266.html](http://www.washingtonpost.com/wp-dyn/content/article/2007/12/17/AR2007121701266.html) > [@](#): > > A jet of highly charged radiation from a supermassive black hole at the center of a distant galaxy is blasting another galaxy nearby – an act of galactic violence that astronomers said yesterday they have never seen before. > > Using images from the orbiting Chandra X-Ray Observatory and other sources, scientists said the extremely intense jet from the larger galaxy can be seen shooting across 20,000 light-years of space and plowing into the outer gas and dust of the smaller one. > **[Black hole plasma jet reveals twisted magnetic fields](https://www.newscientist.com/article/mg19826535-000-black-hole-plasma-jet-reveals-twisted-magnetic-fields/)** > > Illustration of a "blazar" showing jets of plasma BLACK holes don't just consume everything nearby – occasionally they fire out huge corkscrews of gas. Now the first look down the barrel of one of these jets has uncovered its origins. Theories... > [@](#): > > Theories predict that tightly coiled magnetic fields close to particularly energetic supermassive black holes called blazars might expel jets of plasma into space. So Alan Marscher at Boston University and colleagues used the Very Long Baseline Array (VLBA) radio telescope and other instruments to peer inside a jet from the blazar BL Lacertae, which lies 950 million light years away. > > The team spotted luminous knots of charged gas particles spiralling outward from a flattened disc of spinning material surrounding the black hole. Further away, these focused into narrow jets, just the shape you would expect if coiled magnetic field lines were spewing out the material (Nature, DOI: 10.1038/nature06895). > > As predicted, the jets also spit out material when they strike obstacles in their path. The team saw bright flares near the base of the jet, where the magnetic fields first begin to coil, and a second eruption where pressure differences between the jet and gas in the surrounding galaxy create a shock wave. ---
**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:** [March 15, 2010, 4:34pm UTC](https://boards.straightdope.com/t/black-hole/532469/28 "2010-03-15T16:34:02Z")
> [@](#): > > I thought that rotating black holes were predicted to have a ring-shaped singularity (and that most black holes would be rotating). Is that outdated? > > If we can predict that it is a ring, then can we predict its radius? And doesn’t that mean that there is some “there” there? Yes, most black holes are believed to be rotating (and in fact, rotating at very close to the maximum possible speed). When physicists talk about non-rotating holes, it’s mostly for the sake of simplicity, since most of the features are qualitatively the same. The singularity of a rotating hole is ring-shaped, but there’s still no “there” there: Trying to discuss the location of the singularity is roughly analogous to trying to discuss a latitude of 95 degrees: The language is adequate to say that, but it doesn’t correspond to any actual location. One other point, in response to one of the other posts: I said that there is no _matter_ in a black hole, not that there’s no _mass_. In ordinary physics, the two terms are often used synonymously, but here, there’s a distinction. By “matter”, what I strictly speaking mean is the stress-energy tensor, and one of the first calculations to be done in GR is to show that it is indeed zero everywhere for a Schwarzschild black hole. But there’s still mass as an emergent property of the topological defect of the singularity. ---
**Author:** ![Sailboat](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/sailboat/32/461_2.png) [@Sailboat](https://boards.straightdope.com/u/Sailboat)\ **Post date:** [March 15, 2010, 4:46pm UTC](https://boards.straightdope.com/t/black-hole/532469/29 "2010-03-15T16:46:15Z")
I also hear it’s more correct nowadays to call them “Singularity-Americans.” ---
**Author:** ![Apex\_Rogers](https://avatars.discourse-cdn.com/v4/letter/a/e480ec/32.png) [@Apex\_Rogers](https://boards.straightdope.com/u/Apex_Rogers)\ **Post date:** [March 15, 2010, 5:01pm UTC](https://boards.straightdope.com/t/black-hole/532469/30 "2010-03-15T17:01:52Z")
> [@Whack-a-Mole](#): > > Yes and no. > As **Chronos** noted for a truly massive black hole it is possible to cross the event horizon and not even know it. For most “smaller” black holes the tidal forces at the event horizon would spaghettifi you (gravity reduces the further you are away from the source…BH gravity can be so strong the pull on your feet versus your head [in a feet-first fall] would be so dramatically different you would be stretched out like a piece of spaghetti). I’m having trouble visualizing the difference between the event horizon of a smaller black hole and a huge black hole. Is the event horizon of a smaller BH really a noticeable demarcation? What exactly is noticeable about the small BH’s event horizon that is not noticeable with a giant BH. Is it the tidal forces that have been mentioned? I don’t see any reason to think they would be significantly different at the event horizon than say a small distance past or closer. So is there anything else special about the event horizon other than it marks the point of no return for light? ---
**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:** [March 15, 2010, 5:21pm UTC](https://boards.straightdope.com/t/black-hole/532469/31 "2010-03-15T17:21:15Z")
Think about [escape velocity](http://en.wikipedia.org/wiki/Escape_velocity). > [@](#): > > For a given gravitational potential energy at a given position, the escape velocity is the minimum speed an object without propulsion needs, to be able to “escape” from the gravity (i.e. so that gravity will never manage to pull it back)… > > On the surface of the Earth, the escape velocity is about 11.2 kilometers per second (~6.96 mi/s), which is approximately 34 times the speed of sound (mach 34) and at least 10 times the speed of a rifle bullet. However, at 9,000 km altitude in “space”, it is slightly less than 7.1 km/s. The closer you get to a massive object the more energy you need to escape from its gravitation well. If the object is massive enough, that energy translates to needing to go faster than the speed of light at a certain point. That point is the event horizon. Within the event horizon, no amount of energy is sufficient for escape. Is it noticeable? Theoretically, yes. The volume enclosed by the event horizon is truly black, because no electromagnetic radiation escapes. There’s all sorts of stuff going on with the matter close to the horizon, as in the links I gave above, that would make it impossible to sit just outside and watch, but the demarcation would be awesome. As for tidal forces, someone else can do the math, but the difference in gravitational potential over a very few feet would be significant for many black holes. See [Spaghettification](http://en.wikipedia.org/wiki/Spaghettification). ---
**Author:** ![AClockworkMelon](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/aclockworkmelon/32/10803_2.png) [@AClockworkMelon](https://boards.straightdope.com/u/AClockworkMelon)\ **Post date:** [March 15, 2010, 5:36pm UTC](https://boards.straightdope.com/t/black-hole/532469/32 "2010-03-15T17:36:19Z")
Gravity is felt everywhere, right? I mean, right now, I’m exerting a teeny tiny, itsy bitsy amount of gravitational pull on my laptop, correct? So wouldn’t that mean that **eventually** everything in a given galaxy _will_ be pulled into the black hole at its center? Also: Do all galaxies have black holes at their center? Like, that’s what keeps the galaxy in a cluster? ---
**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:** [March 15, 2010, 5:47pm UTC](https://boards.straightdope.com/t/black-hole/532469/33 "2010-03-15T17:47:16Z")
> [@AClockworkMelon](#): > > So wouldn’t that mean that **eventually** everything in a given galaxy _will_ be pulled into the black hole at its center? Probably not. Look upthread. > [@Ann Neville](#): > > If you had one tennis ball in Philadelphia, and another one in Indianapolis, that would be an approximately proportionate model, in distance and size, between the Sun and Proxima Centauri. Stars are just not going to collide when they’re that far apart. Since the only way a black hole can swallow up a star is for the black hole and the star to collide, that isn’t going to happen in our part of the galaxy either. Gravity is very weak. You can lift your laptop against the entire gravitational pull of the earth. The earth will remain in orbit forever, essentially, against the gravitation pull of the sun. The stars in the galaxy will remain in orbit around the black hole in its center essentially forever, unless they are perturbed by an outside force. They would orbit around the center even if there wasn’t a black hole there. The universe as a whole is expanding so even galaxies won’t squash together in the end (although local groups of galaxies very close together may do so). As also said earlier, black holes are not some magic suction device. They have exactly as much gravity as any other object of that mass. In the context of an entire galaxy, that much mass is trivial. > [@](#): > > Also: Do all galaxies have black holes at their center Most, but not all, I believe is the current understanding. Depends on the size and evolution of the galaxy. ---
**Author:** ![Anne\_Neville](https://avatars.discourse-cdn.com/v4/letter/a/b9e5f3/32.png) [@Anne\_Neville](https://boards.straightdope.com/u/Anne_Neville)\ **Post date:** [March 15, 2010, 5:56pm UTC](https://boards.straightdope.com/t/black-hole/532469/34 "2010-03-15T17:56:49Z")
> [@AClockworkMelon](#): > > I mean, right now, I’m exerting a teeny tiny, itsy bitsy amount of gravitational pull on my laptop, correct? > > So wouldn’t that mean that **eventually** everything in a given galaxy _will_ be pulled into the black hole at its center? No, no more than all the planets will eventually crash into the Sun. You can have stable orbits around a gravitating body. You can have situations like the Earth-Moon system, where tidal forces cause the Moon to move away from the Earth, not toward it. Or stars could get thrown into intergalactic space as a result of galaxy collisions. [These galaxies](http://en.wikipedia.org/wiki/Antennae_Galaxies) are colliding, and you can see the long tails of stars and stuff thrown out of them. Galaxy collisions are much more frequent than collisions between stars. ---
**Author:** ![AClockworkMelon](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/aclockworkmelon/32/10803_2.png) [@AClockworkMelon](https://boards.straightdope.com/u/AClockworkMelon)\ **Post date:** [March 15, 2010, 6:02pm UTC](https://boards.straightdope.com/t/black-hole/532469/35 "2010-03-15T18:02:48Z")
Is it still a popular theory among scientists that our big bang was the creation of a black hole in another universe? (I’m not even sure if this was ever a popular theory among scientists. But I vaguely remember reading that it was.) And the matter pulled into black holes in our universe is being spewed out into other universes? _Veering further off-topic._ ---
**Author:** ![Mr.Excellent](https://avatars.discourse-cdn.com/v4/letter/m/f19dbf/32.png) [@Mr.Excellent](https://boards.straightdope.com/u/Mr.Excellent)\ **Post date:** [March 15, 2010, 6:10pm UTC](https://boards.straightdope.com/t/black-hole/532469/36 "2010-03-15T18:10:08Z")
Assuming tidal forces didn’t rip it into tiny shreds, is there any reason that a spacecraft could not maintain an orbit as long as it wished _inside_ a black hole’s event horizon? How freely could it adjust its orbit? Or is even the maintenance of an orbital velocity impossible inside the event horizon? ---
**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:** [March 15, 2010, 6:21pm UTC](https://boards.straightdope.com/t/black-hole/532469/37 "2010-03-15T18:21:28Z")
> [@AClockworkMelon](#): > > Is it still a popular theory among scientists that our big bang was the creation of a black hole in another universe? (I’m not even sure if this was ever a popular theory among scientists. But I vaguely remember reading that it was.) And the matter pulled into black holes in our universe is being spewed out into other universes? > > _Veering further off-topic._ It is not a popular theory. If this were the case we should see “[white holes](http://en.wikipedia.org/wiki/White_hole)” in our universe spewing out matter but we do not see anything like that out there. ---
**Author:** ![Tom\_Tildrum](https://avatars.discourse-cdn.com/v4/letter/t/e95f7d/32.png) [@Tom\_Tildrum](https://boards.straightdope.com/u/Tom_Tildrum)\ **Post date:** [March 15, 2010, 6:25pm UTC](https://boards.straightdope.com/t/black-hole/532469/38 "2010-03-15T18:25:39Z")
> [@Exapno\_Mapcase](#): > > Is it noticeable? Theoretically, yes. The volume enclosed by the event horizon is truly black, because no electromagnetic radiation escapes. There’s all sorts of stuff going on with the matter close to the horizon, as in the links I gave above, that would make it impossible to sit just outside and watch, but the demarcation would be awesome. You would suddenly be awash in light that was unable to pass the event horizon, correct? In theory, the inside of the event horizon of a black hole could be brightly lit, yes? Or am I thinking about this wrong? ---
**Author:** ![Mr.Excellent](https://avatars.discourse-cdn.com/v4/letter/m/f19dbf/32.png) [@Mr.Excellent](https://boards.straightdope.com/u/Mr.Excellent)\ **Post date:** [March 15, 2010, 6:36pm UTC](https://boards.straightdope.com/t/black-hole/532469/39 "2010-03-15T18:36:45Z")
> [@Tom\_Tildrum](#): > > You would suddenly be awash in light that was unable to pass the event horizon, correct? In theory, the inside of the event horizon of a black hole could be brightly lit, yes? Or am I thinking about this wrong? I am not an astrophysicist, but that doesn’t sound right to me. It’s not as if there are a lot of additional light sources inside the black hole - well, actually, there might be, as gases sucked into the hole are still going to be heated by collision and tidal stresses just like outside. But beyond that - why would the sky one foot “beneath” the event horizon look any different than the sky one foot “above”? ---
**Author:** ![The\_Hamster\_King](https://avatars.discourse-cdn.com/v4/letter/t/8edcca/32.png) [@The\_Hamster\_King](https://boards.straightdope.com/u/The_Hamster_King)\ **Post date:** [March 15, 2010, 6:38pm UTC](https://boards.straightdope.com/t/black-hole/532469/40 "2010-03-15T18:38:23Z")
> [@Tom\_Tildrum](#): > > You would suddenly be awash in light that was unable to pass the event horizon, correct? In theory, the inside of the event horizon of a black hole could be brightly lit, yes? Or am I thinking about this wrong? You’re thinking about it wrong. It’s not like the event horizon is a barrier bouncing light back into the interior. Rather it means that once you cross the event horizon there is no path you (or light) can follow that leads to the “outside”. Once you’re inside the event horizon, there are no paths that will increase your distance from the singularity. This is true no matter where you are inside the event horizon. So if you drop a flashing beacon into a black hole and then immediately follow it, you won’t be able to see the beacon. It’s closer to the singularity and it’s light can’t climb back out to where you are even though you’re inside the event horizon as well. [Previous page](https://boards.straightdope.com/t/black-hole/532469.md?page=1) [Next page](https://boards.straightdope.com/t/black-hole/532469.md?page=3)