# Why wouldn't this simple idea to escape a black hole from below the event horizon work? **URL:** \ **Category:** Factual Questions\ **Created:** [August 26, 2009, 8:07pm UTC](https://boards.straightdope.com/t/why-wouldnt-this-simple-idea-to-escape-a-black-hole-from-below-the-event-horizon-work/507809 "2009-08-26T20:07:27Z")\ **Posts on this page:** 20\ **Page:** 3
**Author:** ![billfish678](https://avatars.discourse-cdn.com/v4/letter/b/7bcc69/32.png) [@billfish678](https://boards.straightdope.com/u/billfish678)\ **Post date:** [August 27, 2009, 2:34pm UTC](https://boards.straightdope.com/t/why-wouldnt-this-simple-idea-to-escape-a-black-hole-from-below-the-event-horizon-work/507809/41 "2009-08-27T14:34:47Z")
opps nevermind ---
**Author:** ![Cheesesteak](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/cheesesteak/32/3694_2.png) [@Cheesesteak](https://boards.straightdope.com/u/Cheesesteak)\ **Post date:** [August 27, 2009, 2:54pm UTC](https://boards.straightdope.com/t/why-wouldnt-this-simple-idea-to-escape-a-black-hole-from-below-the-event-horizon-work/507809/42 "2009-08-27T14:54:43Z")
Not an answer, but a thought experiment. If your escape rocket has headlights, will the light escape too? Does it seem reasonable that you could be slowly moving toward the event horizon, and escape, while the light from your headlights cannot, even when you’re just one millimeter from the horizon? ---
**Author:** ![ExTank](https://avatars.discourse-cdn.com/v4/letter/e/35a633/32.png) [@ExTank](https://boards.straightdope.com/u/ExTank)\ **Post date:** [August 27, 2009, 2:58pm UTC](https://boards.straightdope.com/t/why-wouldnt-this-simple-idea-to-escape-a-black-hole-from-below-the-event-horizon-work/507809/43 "2009-08-27T14:58:50Z")
Let’s put the whole mess on a treadmill. Then we’ll _really_ see what’s what. ---
**Author:** ![msmith537](https://avatars.discourse-cdn.com/v4/letter/m/d9b06d/32.png) [@msmith537](https://boards.straightdope.com/u/msmith537)\ **Post date:** [August 27, 2009, 3:01pm UTC](https://boards.straightdope.com/t/why-wouldnt-this-simple-idea-to-escape-a-black-hole-from-below-the-event-horizon-work/507809/44 "2009-08-27T15:01:47Z")
> [@Cheesesteak](#): > > Not an answer, but a thought experiment. If your escape rocket has headlights, will the light escape too? Does it seem reasonable that you could be slowly moving toward the event horizon, and escape, while the light from your headlights cannot, even when you’re just one millimeter from the horizon? No. The rocket doesn’t escape. The light doesn’t escape. You cannot move back towards the event horizon once inside it. It’s not like a well you can just climb out of. ---
**Author:** ![enipla](https://avatars.discourse-cdn.com/v4/letter/e/54ee81/32.png) [@enipla](https://boards.straightdope.com/u/enipla)\ **Post date:** [August 27, 2009, 3:11pm UTC](https://boards.straightdope.com/t/why-wouldnt-this-simple-idea-to-escape-a-black-hole-from-below-the-event-horizon-work/507809/45 "2009-08-27T15:11:45Z")
> [@msmith537](#): > > No. The rocket doesn’t escape. The light doesn’t escape. You cannot move back towards the event horizon once inside it. It’s not like a well you can just climb out of. Even if you had a space elevator made of unobtanium? ---
**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:** [August 27, 2009, 3:14pm UTC](https://boards.straightdope.com/t/why-wouldnt-this-simple-idea-to-escape-a-black-hole-from-below-the-event-horizon-work/507809/46 "2009-08-27T15:14:49Z")
> [@Canadjun](#): > > I’ll let someone else that is in the mood do the searching (the five-minute limit makes SDMB searching crippled and I can’t be bothered figuring out the ins and outs of finding it with Google) but quite a while back there was another question on the exact same topic. Why do I remember? Because I was the OP on the old one. Go back far enough on my posts and you should eventually find it. Here’s the easy way (simple once you know): On a Google search simply type in your terms as usual then add at the end: site:straightdope.com So in a Google search type something like: **black hole canadjun site:straightdope.com** Which gets you this SDMB page as the 4th hit on your search: [Escaping a black hole - Factual Questions - Straight Dope Message Board](http://boards.straightdope.com/sdmb/showthread.php?t=312205) (there is your post) You can of course specify any site you like to restrict the results to that site. ---
**Author:** ![Mosier](https://avatars.discourse-cdn.com/v4/letter/m/7ea924/32.png) [@Mosier](https://boards.straightdope.com/u/Mosier)\ **Post date:** [August 27, 2009, 3:24pm UTC](https://boards.straightdope.com/t/why-wouldnt-this-simple-idea-to-escape-a-black-hole-from-below-the-event-horizon-work/507809/47 "2009-08-27T15:24:31Z")
So the moral of the story is that you can’t even get closer to the event horizon once you’re on the wrong side of it? No matter which direction you try to travel, “down” is always “forward”? ---
**Author:** ![msmith537](https://avatars.discourse-cdn.com/v4/letter/m/d9b06d/32.png) [@msmith537](https://boards.straightdope.com/u/msmith537)\ **Post date:** [August 27, 2009, 3:49pm UTC](https://boards.straightdope.com/t/why-wouldnt-this-simple-idea-to-escape-a-black-hole-from-below-the-event-horizon-work/507809/48 "2009-08-27T15:49:45Z")
> [@enipla](#): > > Even if you had a space elevator made of unobtanium? By unobtanium you mean a material infinitely strong? Interesting. My WAG is that to the observer inside the horizon, the elevator cable would be stretched infinitely long and if they tried to accend it, the end would forever be out of reach. ---
**Author:** ![Yumblie](https://avatars.discourse-cdn.com/v4/letter/y/76d3ee/32.png) [@Yumblie](https://boards.straightdope.com/u/Yumblie)\ **Post date:** [August 27, 2009, 4:08pm UTC](https://boards.straightdope.com/t/why-wouldnt-this-simple-idea-to-escape-a-black-hole-from-below-the-event-horizon-work/507809/49 "2009-08-27T16:08:32Z")
> [@Mosier](#): > > So the moral of the story is that you can’t even get closer to the event horizon once you’re on the wrong side of it? No matter which direction you try to travel, “down” is always “forward”? Right. Crossing the event horizon is like crossing into a whole different universe, one which is in the process of collapsing in a big crunch. You wouldn’t be able to avoid hitting the singularity any more than you would be able to avoid being crunched up in a collapsing universe. ---
**Author:** ![enipla](https://avatars.discourse-cdn.com/v4/letter/e/54ee81/32.png) [@enipla](https://boards.straightdope.com/u/enipla)\ **Post date:** [August 27, 2009, 4:09pm UTC](https://boards.straightdope.com/t/why-wouldnt-this-simple-idea-to-escape-a-black-hole-from-below-the-event-horizon-work/507809/50 "2009-08-27T16:09:32Z")
> [@msmith537](#): > > \By unobtanium you mean a material infinitely strong? Interesting…\ Yes. > [@msmith537](#): > > My WAG is that to the observer inside the horizon, the elevator cable would be stretched infinitely long and if they tried to accend it, the end would forever be out of reach. As a former draftsman, and now GIS (Cartographer, spatial analysis) programmer, I just don’t think I’ll ever be able to understand this. Pretty much my entire life has revolved around being able to define ‘space’, area, length and position. And then releate them to other positions. The unobtanium space elevator has a specific length, after all, we only have so much of the material If you move along the unobtanium space elevator at a certain speed, if one end of it is anchored outside of the EH, certainly you will reach it. (?) 😕 ---
**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:** [August 27, 2009, 4:22pm UTC](https://boards.straightdope.com/t/why-wouldnt-this-simple-idea-to-escape-a-black-hole-from-below-the-event-horizon-work/507809/51 "2009-08-27T16:22:34Z")
> [@enipla](#): > > As a former draftsman, and now GIS (Cartographer, spatial analysis) programmer, I just don’t think I’ll ever be able to understand this. Pretty much my entire life has revolved around being able to define ‘space’, area, length and position. And then releate them to other positions. > > The unobtanium space elevator has a specific length, after all, we only have so much of the material > > If you move along the unobtanium space elevator at a certain speed, if one end of it is anchored outside of the EH, certainly you will reach it. (?) 😕 I _think_ the problem here is the unobtanium itself. We are assuming an impossible material to enable doing something impossible so our brain breaks trying to wrap itself around it (like issues with time travel lead to perplexing dilemmas). I presume the “end” of your unobtaium rope, inside a black hole, ends at the singularity as _all_ paths in the black hole arrive at the singularity. Except here you now have the rope going two places at once…outside the event horizon and to the singularity. An impossibility unobtanium or not. ---
**Author:** ![dracoi](https://avatars.discourse-cdn.com/v4/letter/d/90db22/32.png) [@dracoi](https://boards.straightdope.com/u/dracoi)\ **Post date:** [August 27, 2009, 4:35pm UTC](https://boards.straightdope.com/t/why-wouldnt-this-simple-idea-to-escape-a-black-hole-from-below-the-event-horizon-work/507809/52 "2009-08-27T16:35:18Z")
> [@enipla](#): > > The unobtanium space elevator has a specific length, after all, we only have so much of the material I think what makes this hard to grasp is that we’re talking about a scenario in which space/time itself is fundamentally changed by the proximity to the black hole. As an engineer, you know that any measurement of specific length has to be made relative to some measuring stick. The mass of a kilogram is defined by a specific chunk of metal; if you changed the weight of that chunk of metal, you’d change the definition of the kilgram and change the mass of everything in the universe. A meter is defined as the distance light travels in a certain fraction of time; change the speed of light and you change the definition of a meter. A second is also defined relative to the speed of light in atomic clocks; again, changing the speed of light changes the passage of time. And we already use time to define distance. So, in these circumstances, the black hole has warped both the objects and the physical laws that we might use to measure them. ---
**Author:** ![Brandus](https://avatars.discourse-cdn.com/v4/letter/b/898d66/32.png) [@Brandus](https://boards.straightdope.com/u/Brandus)\ **Post date:** [August 27, 2009, 4:38pm UTC](https://boards.straightdope.com/t/why-wouldnt-this-simple-idea-to-escape-a-black-hole-from-below-the-event-horizon-work/507809/53 "2009-08-27T16:38:21Z")
I think this question is kind of related, but are black holes permanent? Say you have a black hole the size of earth. If an object the size of Jupiter smashed into it at a huge speed, wouldn’t it completely obliterate it? Certainly it wouldn’t remain a perfect sphere, and as it loses its shape, it may no longer have enough gravity to be a black hole. ---
**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:** [August 27, 2009, 4:45pm UTC](https://boards.straightdope.com/t/why-wouldnt-this-simple-idea-to-escape-a-black-hole-from-below-the-event-horizon-work/507809/54 "2009-08-27T16:45:49Z")
> [@Brandus](#): > > I think this question is kind of related, but are black holes permanent? > > Say you have a black hole the size of earth. If an object the size of Jupiter smashed into it at a huge speed, wouldn’t it completely obliterate it? Certainly it wouldn’t remain a perfect sphere, and as it loses its shape, it may no longer have enough gravity to be a black hole. Black Holes are presumed to evaporate via Hawking Radiation. For a very, very, very teeny black hole (i.e. microscopic) it will evaporate in moments. For a stellar mass black hole we are talking times that take us to the end of the universe (100 billion years +) to fully evaporate. Jupiter smacking into an Earth mass black hole would not obliterate the black hole at all. Remember _nothing_ can escape a black hole. Period. If Jupiter whacked into one the black hole would simply start to consume Jupiter. Eventually you would have a Jupiter + Earth mass black hole left sitting there. I think it would take longer than you might suspect to eat Jupiter though since an Earth mass black hole would have a radius of around 1/3 of an inch. ---
**Author:** ![enipla](https://avatars.discourse-cdn.com/v4/letter/e/54ee81/32.png) [@enipla](https://boards.straightdope.com/u/enipla)\ **Post date:** [August 27, 2009, 5:27pm UTC](https://boards.straightdope.com/t/why-wouldnt-this-simple-idea-to-escape-a-black-hole-from-below-the-event-horizon-work/507809/55 "2009-08-27T17:27:14Z")
> [@dracoi](#): > > \A meter is defined as the distance light travels in a certain fraction of time; change the speed of light and you change the definition of a meter.\. While distance is not a human construct, measuring it is. Hence the length of a meter is the length of the path travelled by light in vacuum during a time interval of 1⁄299 792 458 of a second. - (wiki) My mind says ‘so what’. Changing the speed of light, or setting it to zero should not negate the fact that there is still a distance between two points. If we know where the event horizon is, we know its diameter. Originally the ‘standard’ meter was a metal bar, change that to half, and it just means you would travel twice as many meters in the same distance. I’m really not trying to be obtuse. Just a bit dense I suppose. ---
**Author:** ![hobscrk777](https://avatars.discourse-cdn.com/v4/letter/h/a6a055/32.png) [@hobscrk777](https://boards.straightdope.com/u/hobscrk777)\ **Post date:** [August 27, 2009, 5:55pm UTC](https://boards.straightdope.com/t/why-wouldnt-this-simple-idea-to-escape-a-black-hole-from-below-the-event-horizon-work/507809/56 "2009-08-27T17:55:35Z")
> [@The\_Tao\_s\_Revenge](#): > > On earth you want to journey to the moon, but you’re old and frail and would never survive the acceleration needed to reach earth escape velocity. So you develop a fuel energetic enough to give a slow 1.01 G acceleration all the way to the moon. Thus you’ve escaped earth’s gravity without reaching escape velocity. By definition, if you have gone beyond the reach of Earth’s gravitational pull (or at least to the point where its effect is negligible), you have reach the escape velocity. In this case (with an acceleration of 1.01g) you will have reached escape velocity very, very slowly. ---
**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:** [August 27, 2009, 6:04pm UTC](https://boards.straightdope.com/t/why-wouldnt-this-simple-idea-to-escape-a-black-hole-from-below-the-event-horizon-work/507809/57 "2009-08-27T18:04:52Z")
First off, relativity does not allow for the existence of indestructible unobtainium. Asking questions about how such a substance interacts with the laws of physics is meaningless. As another poster once said long ago, “I have a magic box which breaks the laws of physics. Doesn’t that break the laws of physics?”. Second, it is indeed possible to travel a limitless distance away from a mass without ever reaching escape speed. Picture speed limit signs every so often at increasing distances from your object, such that the speed limit is always half of the escape speed at that distance. Now, drive away from the mass at the speed limit. Your speed will be constantly decreasing, as will the thrust from your motor, but you’ll eventually reach infinity that way. ---
**Author:** ![dracoi](https://avatars.discourse-cdn.com/v4/letter/d/90db22/32.png) [@dracoi](https://boards.straightdope.com/u/dracoi)\ **Post date:** [August 27, 2009, 6:06pm UTC](https://boards.straightdope.com/t/why-wouldnt-this-simple-idea-to-escape-a-black-hole-from-below-the-event-horizon-work/507809/58 "2009-08-27T18:06:39Z")
Well, the point is that you reach a point where the warping of space time has warped any instrument you’d use to measure something. Maybe here’s an example that could help. Let’s say you have a steel ladder, and you used a standard meter of the old metal bar type made from the same type of steel. You measure the ladder’s length at room temperature and get 3 meters. Now, you bring the ladder and the meter stick into a sauna and measure again. You still get 3 meters. Now you take them outside and put them in the snow. You still get 3 meters. Yet, we know that metal changes length as it heats and cools. The problem is that your ruler is made of the same metal and will expand proportionately with the ladder. If you want to measure the expansion and contraction of the metal, you need a ruler that is not metal. In the case of relativity, space-time, etc. the problem isn’t metal changing shape, but space itself changing shape. ---
**Author:** ![enipla](https://avatars.discourse-cdn.com/v4/letter/e/54ee81/32.png) [@enipla](https://boards.straightdope.com/u/enipla)\ **Post date:** [August 27, 2009, 6:20pm UTC](https://boards.straightdope.com/t/why-wouldnt-this-simple-idea-to-escape-a-black-hole-from-below-the-event-horizon-work/507809/59 "2009-08-27T18:20:51Z")
> [@Chronos](#): > > First off, relativity does not allow for the existence of indestructible unobtainium. Asking questions about how such a substance interacts with the laws of physics is meaningless. As another poster once said long ago, “I have a magic box which breaks the laws of physics. Doesn’t that break the laws of physics?”. Ok. I was just using that to draw a straight line from the singularity to a point outside the EH. If people are saying that it’s impossible to travel in a straight line, well, travel in a curve to the point outside of the EH. Why is this supposedly a one way door? > [@Chronos](#): > > Second, it is indeed possible to travel a limitless distance away from a mass without ever reaching escape speed. Picture speed limit signs every so often at increasing distances from your object, such that the speed limit is always half of the escape speed at that distance. Now, drive away from the mass at the speed limit. Your speed will be constantly decreasing, as will the thrust from your motor, but you’ll eventually reach infinity that way. Fine again. Just like jumping have the distance to the wall. You never reach it. But if you travel at 1mph away from the center of the earth for a long enough time you will escape earths gravitational pull. I guess you could say your escape velocity in this instance would be 1mph. ---
**Author:** ![Frylock](https://avatars.discourse-cdn.com/v4/letter/f/ce7236/32.png) [@Frylock](https://boards.straightdope.com/u/Frylock)\ **Post date:** [August 27, 2009, 6:38pm UTC](https://boards.straightdope.com/t/why-wouldnt-this-simple-idea-to-escape-a-black-hole-from-below-the-event-horizon-work/507809/60 "2009-08-27T18:38:01Z")
> [@Yumblie](#): > > This is what is meant when it’s sometimes said that space and time switch places. The bottom of the black hole becomes a point in the future rather than a typical point in space, since inside, all possible paths through space-time eventually lead to it. Wait, is this for reals? What I mean is, does the math really represent things this way–a point in space becoming a point in future time instead? [Previous page](https://boards.straightdope.com/t/why-wouldnt-this-simple-idea-to-escape-a-black-hole-from-below-the-event-horizon-work/507809.md?page=2) [Next page](https://boards.straightdope.com/t/why-wouldnt-this-simple-idea-to-escape-a-black-hole-from-below-the-event-horizon-work/507809.md?page=4)