# Orbiting a black hole inside the event horizon until it "evaporates" **URL:** \ **Category:** Factual Questions\ **Created:** [June 10, 2012, 12:01pm UTC](https://boards.straightdope.com/t/orbiting-a-black-hole-inside-the-event-horizon-until-it-evaporates/624709 "2012-06-10T12:01:15Z")\ **Posts on this page:** 20\ **Page:** 1
**Author:** ![HMS\_Irruncible](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/hms_irruncible/32/7394_2.png) [@HMS\_Irruncible](https://boards.straightdope.com/u/HMS_Irruncible)\ **Post date:** [June 10, 2012, 12:01pm UTC](https://boards.straightdope.com/t/orbiting-a-black-hole-inside-the-event-horizon-until-it-evaporates/624709/1 "2012-06-10T12:01:15Z")
I’ve learned recently that objects can cross into the event horizon of a black hole without being destroyed. Would it then be possible to orbit the singularity until it evaporated, and in that matter “escape” the event horizon? Or, varation 2, if the energy to achieve orbit is infinite, but let’s say the timing is fortunate enough that the singularity evaporates sometime between the spacecraft’s event horizon transit and its destruction. I suppose this has already been imagined and discarded, so I guess the question is really what part of this scenario is wrong or impossible. ---
**Author:** ![Ken001](https://avatars.discourse-cdn.com/v4/letter/k/43a26b/32.png) [@Ken001](https://boards.straightdope.com/u/Ken001)\ **Post date:** [June 10, 2012, 12:12pm UTC](https://boards.straightdope.com/t/orbiting-a-black-hole-inside-the-event-horizon-until-it-evaporates/624709/2 "2012-06-10T12:12:21Z")
No. If you are within the event horizon then time has slowed down for you and it doesn’t matter when evaporation occurs, you are part of it. Besides, the evaporation of a black hole is something which you can envisage as finally taking place towards the heat death of the universe. A long long way in the future. ---
**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:** [June 10, 2012, 12:18pm UTC](https://boards.straightdope.com/t/orbiting-a-black-hole-inside-the-event-horizon-until-it-evaporates/624709/3 "2012-06-10T12:18:39Z")
> [@Ken001](#): > > Besides, the evaporation of a black hole is something which you can envisage as finally taking place towards the heat death of the universe. A long long way in the future. Nitpick: The evaporation of a black hole large enough that you could possibly enter the event horizon and survive will take that long to evaporate. A micro black hole if they exist or can be made could evaporate much sooner; but you aren’t going to survive passage into a black hole the size of a pinhead or subatomic particle. ---
**Author:** ![The\_Tao\_s\_Revenge](https://avatars.discourse-cdn.com/v4/letter/t/73ab20/32.png) [@The\_Tao\_s\_Revenge](https://boards.straightdope.com/u/The_Tao_s_Revenge)\ **Post date:** [June 10, 2012, 12:19pm UTC](https://boards.straightdope.com/t/orbiting-a-black-hole-inside-the-event-horizon-until-it-evaporates/624709/4 "2012-06-10T12:19:34Z")
Also there is no stable orbit in an event horizon. The space you are in is moving toward the singularity faster than light. To have a stable orbit, you’d need to move faster than light. > [@Der\_Trihs](#): > > Nitpick: The evaporation of a black hole large enough that you could possibly enter the event horizon and survive will take that long to evaporate. A micro black hole if they exist or can be made could evaporate much sooner; but you aren’t going to survive passage into a black hole the size of a pinhead or subatomic particle. There’s your answer. Just be bigger than the black hole’s event horizon, and move away quickly, and most of your body will survive. Also known as the Apache Chief school of black hole survival. ---
**Author:** ![Fear\_Itself](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/fear_itself/32/19637_2.png) [@Fear\_Itself](https://boards.straightdope.com/u/Fear_Itself)\ **Post date:** [June 10, 2012, 12:21pm UTC](https://boards.straightdope.com/t/orbiting-a-black-hole-inside-the-event-horizon-until-it-evaporates/624709/5 "2012-06-10T12:21:49Z")
> [@Cosmic Relief](#): > > I’ve learned recently that objects can cross into the event horizon of a black hole without being destroyed. I don’t think this is true. ---
**Author:** ![The\_Tao\_s\_Revenge](https://avatars.discourse-cdn.com/v4/letter/t/73ab20/32.png) [@The\_Tao\_s\_Revenge](https://boards.straightdope.com/u/The_Tao_s_Revenge)\ **Post date:** [June 10, 2012, 12:35pm UTC](https://boards.straightdope.com/t/orbiting-a-black-hole-inside-the-event-horizon-until-it-evaporates/624709/6 "2012-06-10T12:35:54Z")
> [@Fear\_Itself](#): > > I don’t think this is true. I think the OP meant immediately destroyed. Or “without being destroyed” in sense that we ask “Will I survive?” even though everyone eventually dies. In a super massive black hole the transition into the event horizon is calculated to be quite comfortable, as far as tidal forces go. ---
**Author:** ![HMS\_Irruncible](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/hms_irruncible/32/7394_2.png) [@HMS\_Irruncible](https://boards.straightdope.com/u/HMS_Irruncible)\ **Post date:** [June 10, 2012, 12:55pm UTC](https://boards.straightdope.com/t/orbiting-a-black-hole-inside-the-event-horizon-until-it-evaporates/624709/7 "2012-06-10T12:55:58Z")
> [@Ken001](#): > > If you are within the event horizon then time has slowed down for you and it doesn’t matter when evaporation occurs, you are part of it. I don’t think this is correct. Yes, to the external world, time has essentially stopped for me, the observer inside the event horizon. And to me, the world outside the event horizon is effectively so far in the future that it isn’t there anymore. But in my here-and-how, local time seems to pass as usual. That’s just “Black Holes 101” from the Wikipedia [article](http://en.wikipedia.org/wiki/Event_horizon): > [@](#): > > An observer crossing a black hole event horizon can calculate the moment they’ve crossed it, but will not actually see or feel anything special happen at that moment. In terms of visual appearance, observers who fall into the hole perceive the black region constituting the horizon as lying at some apparent distance below them, and never experience crossing this visual horizon.[7] Other objects that had entered the horizon along the same radial path but at an earlier time would appear below the observer but still above the visual position of the horizon, and if they had fallen in recently enough the observer could exchange messages with them before either one was destroyed by the gravitational singularity.[8] Increasing tidal forces (and eventual impact with the hole’s singularity) are the only locally noticeable effects. > [@](#): > > Besides, the evaporation of a black hole is something which you can envisage as finally taking place towards the heat death of the universe. A long long way in the future. This isn’t really true of all black holes, as I understand. If they are sufficiently small, then they can evaporate quite readily. Of course that may only be true of singularities so small that their event horizons do not extend past the singularity itself, I’m not sure about that. ---
**Author:** ![HMS\_Irruncible](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/hms_irruncible/32/7394_2.png) [@HMS\_Irruncible](https://boards.straightdope.com/u/HMS_Irruncible)\ **Post date:** [June 10, 2012, 1:00pm UTC](https://boards.straightdope.com/t/orbiting-a-black-hole-inside-the-event-horizon-until-it-evaporates/624709/8 "2012-06-10T13:00:24Z")
> [@The\_Tao\_s\_Revenge](#): > > I think the OP meant immediately destroyed. Or “without being destroyed” in sense that we ask “Will I survive?” even though everyone eventually dies. > > In a super massive black hole the transition into the event horizon is calculated to be quite comfortable, as far as tidal forces go. Right and right. You can never exit the event horizon, that’s a given, but you can exist normally for some amount of time(space?). So my question is, what could happen if that black hole evaporated between entering the event horizon and impact with the singularity. And I understand that evaporation takes a really, really long time by any external measure, but once you’ve entered an event horizon, hasn’t the apparent passage of external time accelerated enough to ensure that even a tiny amount of passage of your subjective time would be equivalent to billions of years of time outside the event horizon? ---
**Author:** ![Fear\_Itself](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/fear_itself/32/19637_2.png) [@Fear\_Itself](https://boards.straightdope.com/u/Fear_Itself)\ **Post date:** [June 10, 2012, 1:44pm UTC](https://boards.straightdope.com/t/orbiting-a-black-hole-inside-the-event-horizon-until-it-evaporates/624709/9 "2012-06-10T13:44:40Z")
> [@The\_Tao\_s\_Revenge](#): > > I think the OP meant immediately destroyed. Or “without being destroyed” in sense that we ask “Will I survive?” even though everyone eventually dies. > > In a super massive black hole the transition into the event horizon is calculated to be quite comfortable, as far as tidal forces go. Tidal forces are not the problem. The event horizon is surrounded by gases orbiting at such high temperature they produce X-rays; I don’t think any non-gaseous object smaller than a planetesimal would survive the transition. ---
**Author:** ![HMS\_Irruncible](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/hms_irruncible/32/7394_2.png) [@HMS\_Irruncible](https://boards.straightdope.com/u/HMS_Irruncible)\ **Post date:** [June 10, 2012, 2:07pm UTC](https://boards.straightdope.com/t/orbiting-a-black-hole-inside-the-event-horizon-until-it-evaporates/624709/10 "2012-06-10T14:07:00Z")
> [@Fear\_Itself](#): > > Tidal forces are not the problem. The event horizon is surrounded by gases orbiting at such high temperature they produce X-rays; Only if it’s accreting, though, right? There would be nothing orbiting a black hole that had already eaten everything in its neighborhood. ---
**Author:** ![The\_Tao\_s\_Revenge](https://avatars.discourse-cdn.com/v4/letter/t/73ab20/32.png) [@The\_Tao\_s\_Revenge](https://boards.straightdope.com/u/The_Tao_s_Revenge)\ **Post date:** [June 10, 2012, 2:12pm UTC](https://boards.straightdope.com/t/orbiting-a-black-hole-inside-the-event-horizon-until-it-evaporates/624709/11 "2012-06-10T14:12:44Z")
> [@Cosmic Relief](#): > > I don’t think this is correct. Yes, to the external world, time has essentially stopped for me, the observer inside the event horizon. And to me, the world outside the event horizon is effectively so far in the future that it isn’t there anymore. But in my here-and-how, local time seems to pass as usual. That’s just “Black Holes 101” from the Wikipedia [article](http://en.wikipedia.org/wiki/Event_horizon): > > This isn’t really true of all black holes, as I understand. If they are sufficiently small, then they can evaporate quite readily. Of course that may only be true of singularities so small that their event horizons do not extend past the singularity itself, I’m not sure about that. I think, and ANAP (and a real one please correct me if I’m wrong) but you need a good explanation of Hawking radiation. According to quantum mechanics, there are virtual particles constantly popping in and out existence. They come in pairs. One made of positive mass, like you, me, the sun, Helen Hunt, your BFF Jill, Antimatter produced in particle accelerates, natural antimatter, and even fig newtons are made of. However we have this stupid rule of conservation of mass. Fucking universe. Anyway to balance the books the other particle is made of negative mass. Therefore the sum total of mass in the universe is the same. They quickly come together and cancel out. +1 + -1 = nothing. There is only one known process that can prevent them from canceling out. A black hole. The gravity is so strong that it can pull them apart. The black hole eats the negative mass, freeing the +particle to become a real [del]boy[/del] particle release into the universe. So, lets say you some how achieve stable orbit, and you’re orbiting the black hole waiting for it to evaporate. You will feel a rain of negative mass. It will cancel out your ships hull. It cancel out your space suit, it will cancel out you, just as if you and the black hole were one. Your ass will cash the check those particles wrote. Larger black holes take longer to evaporate because they have so much mass relative to surface area. Mice and men have a similar problem. Small animals lose heat a lot faster because the have a lot of surface area relative to their mass. **Fear Itself** , I don’t think that’s a strict requirement of black holes. I don’t think there’s a law saying you can’t have a black hole without things in orbit of it. Further I think if you accept the building of a space craft reaching the black hole, you can accept one with a hull of sufficient engineering/mass whatever to survive. ---
**Author:** ![Fear\_Itself](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/fear_itself/32/19637_2.png) [@Fear\_Itself](https://boards.straightdope.com/u/Fear_Itself)\ **Post date:** [June 10, 2012, 2:14pm UTC](https://boards.straightdope.com/t/orbiting-a-black-hole-inside-the-event-horizon-until-it-evaporates/624709/12 "2012-06-10T14:14:42Z")
> [@Cosmic Relief](#): > > Only if it’s accreting, though, right? There would be nothing orbiting a black hole that had already eaten everything in its neighborhood. I don’t think that is possible. Most of the mass in the universe is interstellar hydrogen. I don’t think a black hole could ever sop up everything in its neighborhood, which is always expanding as the black hole gains mass. ---
**Author:** ![Fear\_Itself](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/fear_itself/32/19637_2.png) [@Fear\_Itself](https://boards.straightdope.com/u/Fear_Itself)\ **Post date:** [June 10, 2012, 2:17pm UTC](https://boards.straightdope.com/t/orbiting-a-black-hole-inside-the-event-horizon-until-it-evaporates/624709/13 "2012-06-10T14:17:11Z")
> [@The\_Tao\_s\_Revenge](#): > > Further I think if you accept the building of a space craft reaching the black hole, you can accept one with a hull of sufficient engineering/mass whatever to survive. I was just addressing the statement in the OP, that made it sound like unobtainium was not required in the real world. ---
**Author:** ![The\_Tao\_s\_Revenge](https://avatars.discourse-cdn.com/v4/letter/t/73ab20/32.png) [@The\_Tao\_s\_Revenge](https://boards.straightdope.com/u/The_Tao_s_Revenge)\ **Post date:** [June 10, 2012, 2:19pm UTC](https://boards.straightdope.com/t/orbiting-a-black-hole-inside-the-event-horizon-until-it-evaporates/624709/14 "2012-06-10T14:19:47Z")
> [@The\_Tao\_s\_Revenge](#): > > Larger black holes take longer to evaporate because they have so much mass relative to surface area. I should say relative to the surface area of their event horizon. ---
**Author:** ![Terr](https://avatars.discourse-cdn.com/v4/letter/t/839c29/32.png) [@Terr](https://boards.straightdope.com/u/Terr)\ **Post date:** [June 10, 2012, 2:33pm UTC](https://boards.straightdope.com/t/orbiting-a-black-hole-inside-the-event-horizon-until-it-evaporates/624709/15 "2012-06-10T14:33:46Z")
I don’t think you can cross the event horizon of a black hole, no matter how big it is, and “survive” in any meaningful manner. As you approach the even horizon, your speed approaches c. That’s because the gravitational acceleration at the event horizon approaches infinity. (If you don’t think so, consider that if it didn’t, if you were at exactly the black hole’s event horizon, you could escape it by accelerating at more than the gravitational acceleration). So, as you cross the event horizon, your speed is c (or, some people who recoil from matter traveling at c claim, infinitesimally less than c). At c, the time contracts to 0 - so for you, as you cross the event horizon, there will be no time at all until you reach the singularity at the center. Or, if you prefer, the time until you reach the singularity at the center would be infinitesimally small. ---
**Author:** ![The\_Tao\_s\_Revenge](https://avatars.discourse-cdn.com/v4/letter/t/73ab20/32.png) [@The\_Tao\_s\_Revenge](https://boards.straightdope.com/u/The_Tao_s_Revenge)\ **Post date:** [June 10, 2012, 2:51pm UTC](https://boards.straightdope.com/t/orbiting-a-black-hole-inside-the-event-horizon-until-it-evaporates/624709/16 "2012-06-10T14:51:17Z")
> [@Terr](#): > > I don’t think you can cross the event horizon of a black hole, no matter how big it is, and “survive” in any meaningful manner. > > As you approach the even horizon, your speed approaches c. That’s because the gravitational acceleration at the event horizon approaches infinity. (If you don’t think so, consider that if it didn’t, if you were at exactly the black hole’s event horizon, you could escape it by accelerating at more than the gravitational acceleration). > > So, as you cross the event horizon, your speed is c (or, some people who recoil from matter traveling at c claim, infinitesimally less than c). At c, the time contracts to 0 - so for you, as you cross the event horizon, there will be no time at all until you reach the singularity at the center. Or, if you prefer, the time until you reach the singularity at the center would be infinitesimally small. I think that’s an interesting thought. Traveling at C requires infinite energy. Potential energy has mass. Therefore if an object falling into a black hole will achieve C any object with the gravitational potential to fall into a black hole has infinite mass. Any object with a black hole in its future light cone could fall into one. It stands to reason there’s no prefer about it. You will never achieve C from falling into a black hole, or black holes do not exist. Edit: I hope I’m wrong, because whatever made me wrong would be really cool. ---
**Author:** ![The\_Tao\_s\_Revenge](https://avatars.discourse-cdn.com/v4/letter/t/73ab20/32.png) [@The\_Tao\_s\_Revenge](https://boards.straightdope.com/u/The_Tao_s_Revenge)\ **Post date:** [June 10, 2012, 3:00pm UTC](https://boards.straightdope.com/t/orbiting-a-black-hole-inside-the-event-horizon-until-it-evaporates/624709/17 "2012-06-10T15:00:23Z")
> [@The\_Tao\_s\_Revenge](#): > > I think that’s an interesting thought. Traveling at C requires infinite energy. Potential energy has mass. Therefore if an object falling into a black hole will achieve C any object with the gravitational potential to fall into a black hole has infinite mass. Any object with a black hole in its future light cone could fall into one. It stands to reason there’s no prefer about it. You will never achieve C from falling into a black hole, or black holes do not exist. > > Edit: I hope I’m wrong, because whatever made me wrong would be really cool. I would like to punch who ever decided the edit window should only be 5 minutes right in the sex organs so hard aliens on the other side of the galaxy instinctively wince in pain, but they do not know why, only that a great act of suffering has happened. Frustrating for the absent minded. Specifically, it should say: I think that’s an interesting thought. Traveling at C requires infinite energy. Potential energy has mass. Therefore if an object falling into a black hole will achieve C any object with the gravitational potential to fall into a black hole has infinite mass. Any object with a black hole in its future light cone could fall into one. It stands to reason there’s no prefer about it. **since we are not all collapsing into black holes ourselves due to infinite mass it stands to reason y** ou will never achieve C from falling into a black hole, or black holes do not exist. ---
**Author:** ![HMS\_Irruncible](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/hms_irruncible/32/7394_2.png) [@HMS\_Irruncible](https://boards.straightdope.com/u/HMS_Irruncible)\ **Post date:** [June 10, 2012, 3:03pm UTC](https://boards.straightdope.com/t/orbiting-a-black-hole-inside-the-event-horizon-until-it-evaporates/624709/18 "2012-06-10T15:03:24Z")
> [@The\_Tao\_s\_Revenge](#): > > I think that’s an interesting thought. Traveling at C requires infinite energy. Potential energy has mass. Therefore if an object falling into a black hole will achieve C any object with the gravitational potential to fall into a black hole has infinite mass. Any object with a black hole in its future light cone could fall into one. It stands to reason there’s no prefer about it. You will never achieve C from falling into a black hole, or black holes do not exist. Agreed. Crossing the event horizon does not imply acceleration to C at that moment. The inability to escape the event horizon isn’t due to the speed the object has reached. It’s just that you have now entered a gravitational field capable of ultimately accelerating an object to C. That doesn’t mean you’re instantly accelerated to C, but it does mean that is unavoidably in your future. ---
**Author:** ![The\_Tao\_s\_Revenge](https://avatars.discourse-cdn.com/v4/letter/t/73ab20/32.png) [@The\_Tao\_s\_Revenge](https://boards.straightdope.com/u/The_Tao_s_Revenge)\ **Post date:** [June 10, 2012, 3:16pm UTC](https://boards.straightdope.com/t/orbiting-a-black-hole-inside-the-event-horizon-until-it-evaporates/624709/19 "2012-06-10T15:16:20Z")
> [@The\_Tao\_s\_Revenge](#): > > I would like to punch who ever decided the edit window should only be 5 minutes right in the sex organs so hard aliens on the other side of the galaxy instinctively wince in pain, but they do not know why, only that a great act of suffering has happened. Frustrating for the absent minded. > > Specifically, it should say: > I think that’s an interesting thought. Traveling at C requires infinite energy. Potential energy has mass. Therefore if an object falling into a black hole will achieve C any object with the gravitational potential to fall into a black hole has infinite mass. Any object with a black hole in its future light cone could fall into one. It stands to reason there’s no prefer about it. **since we are not all collapsing into black holes ourselves due to infinite mass it stands to reason y** ou will never achieve C from falling into a black hole, or black holes do not exist. Even then I was not complete! I am not good at this communicating my thoughts thing.:smack: It should be noted the speed of light thing only applies to objects with standard mass. Objects without mass, like photons, travel at C. ---
**Author:** ![billfish678](https://avatars.discourse-cdn.com/v4/letter/b/7bcc69/32.png) [@billfish678](https://boards.straightdope.com/u/billfish678)\ **Post date:** [June 10, 2012, 3:21pm UTC](https://boards.straightdope.com/t/orbiting-a-black-hole-inside-the-event-horizon-until-it-evaporates/624709/20 "2012-06-10T15:21:00Z")
> [@Fear\_Itself](#): > > I don’t think that is possible. Most of the mass in the universe is interstellar hydrogen. I don’t think a black hole could ever sop up everything in its neighborhood, which is always expanding as the black hole gains mass. If you have a black hole way out in interstellar space I am pretty sure its not going to have enough hydrogen around it to suck up to create a radiation producing accretion disk. Interstellar space is extremely empty. [Next page](https://boards.straightdope.com/t/orbiting-a-black-hole-inside-the-event-horizon-until-it-evaporates/624709.md?page=2)