<p>This is more of a physics question than it is astronomy, but nevertheless, think of it this way (most of what I say requires verification as I am not qualified to give a 100% correct in details answer): Light can't escape a black hole, and no propulsion system can accelerate an object to the speed of light. The faster you go, the more you weigh, the more force you have to input to maintain acceleration, the more energy you waste over time. If drawn on a graph, the energy required to increase speed by dX when at speed X, the graph has an asymptote at the speed of light. Meaning that it won't reach it no matter how much energy is input. </p>

<p>Take a look at LHC, where hadrons are accelerated to such a point when not their speed is measured anymore, because it hardly changes, but rather the energy of the particles, which increases a lot when approaching the speed of light. This will give you perspective about how unreachable it is.</p>

<p>So, if you can't accelerate to the speed of light then you, like light, are trapped inside the event horizon.</p>

<p>Also, AFAIK, light doesn't exit not because photons have weight, but because time stops. So light doesn't travel, nothing happens because there is no time.</p>

<p>Again, I'm not qualified. I just like to read about this stuff.</p>

CC BY-SA 3.0
2016-12-16T08:56:10.230Z
There is not a lot that is relevant to the question here. Black holes are a General Relativistic phenomenon.
ProfRob
CC BY-SA 3.0
2013-11-25T12:20:59.360Z
My question revolves around my understanding that an escape velocity is an initial velocity, that without any additional acceleration is sufficient to escape the gravitational pull of a planet.  So, for example, if we had a good enough power source and reaction mass, we should be able to get arbitrarily far from the earth, while moving at a constant slow speed.  Correspondingly could this work with a black hole, or is there something about the curvature of space that makes escape impossible.
Mitchell Kaplan
CC BY-SA 3.0
2013-11-25T18:10:23.167Z
Like I've explained, you can't even reach the speed of light, and not even light can escape. There is nothing you could to to reach the speed of light. You need an infinite amount of energy to do this, which means in other words that it's impossible.
Also, movement is described as a change in position in a time limit, and is defined by speed (t^-1), acceleration (t^-2) and higher level equations (t^-n), which are all dependent on time (t). Well beyond the event horizon there is no time, so "movement" doesn't make any sense as a concept.
Alex
CC BY-SA 3.0
2014-01-05T17:02:06.577Z
Hmm, photons follow null geodesics of space-time. Why do you say that time stops? Also, what do you mean by this? Do you mean time as seen by an observer outside of the event horizon, or do you mean the local coordinate time of somebody who has fallen in. I think that part of your answer should be omitted.
astromax
CC BY-SA 3.0
2013-11-25T05:27:02.417Z
2013-11-25T05:27:02.417Z
Alex
<p>Although I partially agree with @Alexander here are a few more things. </p>

<p>According to Einstein's <strong>special theory of relativity</strong>, particles cannot travel at the speed of light (c). It would take infinite energy as stated above. However, the special theory of relativity states that an object can travel <strong>slower or faster</strong> than the speed of light but not at the speed of c. We may refer to the objects that travel faster than the speed of light as <strong>tachyons</strong>. There are celestial objects which are accelerated faster than the speed of light. </p>

<p>A common thing that everyone says is that nothing can escape a blackhole. But it is totally <a href="http://www.space.com/16867-black-holes-quantum-mechanics-theory.html" rel="nofollow">wrong</a>. Blackholes do emit particles and radiation called as <strong>Hawking radiation</strong>. Even stephen hawking has changed  his mind about blackholes as the general concept that blackholes absorb everything can be disproved by quantum mechanics theories.</p>

<p><strong>So, If there exists a possibility that we can indeed escape a blackhole.</strong></p>

<p>At <strong>CERN,</strong> <a href="http://news.nationalgeographic.co.in/news/2011/09/110923-neutrinos-speed-of-light-particles-cern-physics-einstein-science/" rel="nofollow">reports</a> says that <strong>ghostly subatomic  particles</strong> called <strong>neutrinos</strong> were observed to travel faster than light. Researches are still trying to confirm it. </p>

<p>There is also another possible theory existing around the scientific community is the concept of wormholes. If a ship were trying to escape a blackhole, opening a wormhole to escape the blackhole and reaching another spot is a proposed theory. </p>

<p>There are also researches that say that objects are <a href="http://science.time.com/2012/10/04/how-to-escape-from-a-black-hole/" rel="nofollow">emanated from blackhole</a>.</p>

CC BY-SA 3.0
2013-11-26T12:26:11.773Z
I think they've discovered an experimental error at CERN, something about the timing of the 2 clocks.  So they no longer think that the neutrinos may have traveled faster than light.  I think the things emanating from black holes are 1/2 of the virtual particle pairs that spontaneously appear in empty space, when a particular pair appears right outside the event horizon.  I'm wondering if you need to be moving anywhere near c to escape a black hole as long as you can apply continuous acceleration.  @AlexanderMP's comment about "time" may be my answer.  But I also wonder about curvature.
Mitchell Kaplan
CC BY-SA 3.0
2013-11-26T12:51:05.863Z
Although neutrino's have been proven wrong, the concept of tachyons still exist. One thing is for sure that there exists no element on earth to build a ship that can escape a blackhole even if we were able to harness the energy to do so. @MitchellKaplan  The **final results** were that neutrino speed were **equal to light**. The margin of error was 15ns.
Mahe
CC BY-SA 3.0
2013-11-27T01:32:39.977Z
@Mahe tachyons are not particles, they are instabilities, and the Hawking radiation arises not from the inside of the black hole but from the event horizon or slightly above.
Dilaton
CC BY-SA 3.0
2014-01-05T16:55:44.197Z
@mahe, Where are you getting that special relativity says things can travel faster than the speed of light? This is completely incorrect. Also, neutrinos were not traveling at or faster than the speed of light once the connection error in the OPERA experiment was fixed. Neutrinos have mass - they do not travel at c.
astromax
CC BY-SA 3.0
2014-01-05T16:57:18.187Z
Your comment about nothing escaping a blackhole is also misguided - see @Dilaton's response to it. Black holes are said to evaporate, but that doesn't mean that the things that were going in are now coming out (see Hawking Radiation - http://en.wikipedia.org/wiki/Hawking_radiation).
astromax
CC BY-SA 3.0
2014-06-20T18:22:24.897Z
There's so much wrong with the answer, I don't even know where to begin. Please don't speculate, this is science, not a layman's guessing game.
Florin Andrei
CC BY-SA 3.0
2014-06-21T20:37:28.650Z
Please improve this answer or it will continue to be down voted or even deleted.
Jeremy
CC BY-SA 3.0
2014-08-10T22:07:41.980Z
The TIME article also is completely unhelpful. The original question was related to escape from inside the black hole, not from outside. And the error regarding Hawking radiation. . . oy.
HDE 226868
CC BY-SA 3.0
2013-11-26T06:01:32.877Z
2013-11-26T06:01:32.877Z
Mahe
<p>One of the clearest way to see what's going on is to look at a Penrose diagram of a Schwarzschild black hole. A Penrose diagram is like a map of the spacetime drawn in such a way as to preserve angles and put the light rays diagonally at $45^\circ$ angles, forming the light cones.</p>

<p>Since we're mapping all of an infinite space(time) into a finite drawing, distances are necessarily distorted, but that's a small price to pay.</p>

<p><img src="https://i.sstatic.net/UwOxF.gif" alt="Schwarzschild causal diagram, original by Andrew Hamilton"></p>

<p>Time goes up on the diagram, and a typical infalling trajectory is in blue.</p>

<p>Because every massive object must be locally slower than light, it must stay within those light cones. Hence, no matter how you accelerate, at every point of your trajectory you must go in a direction that stays within those $45^\circ$ diagonals at that point. But once you're inside the horizon, every direction that stays within the light cones leads to the singularity.</p>

<p>Accelerating this way or that just means that you get to choose where you hit the singularity--a little on the left on the diagram or a little to the right. Trying to escape using high acceleration brings you closer to the light's $45^\circ$ lines, which because of time dilation will actually <em>shorten</em> your lifespan. You'll actually get to the singularity <em>sooner</em> if you struggle in that manner.</p>

<p>This particular image came from Prof. <a href="http://casa.colorado.edu/~ajsh/home.html" rel="noreferrer">Andrew Hamilton</a>. Note that it pictures an <em>eternal</em> Schwarzschild black hole, i.e. one that has always and will exist. An actual black hole is formed by stellar collapse and will eventually evaporate, so its diagram will be slightly different (in particular, there will be no "antihorizon"). However, in all respects relevant here, it's the same situation.</p>

CC BY-SA 4.0
2019-01-29T23:58:19.540Z
Could you elaborate on how it's "the same situation" despite the black hole eventually evaporating, given that the singularity itself seems to actually reside an infinite time in the future, according to the diagram? (or at least according one understandable, though potentially naive, interpretation of the diagram)
mtraceur
CC BY-SA 3.0
2013-12-22T02:38:47.537Z
2013-12-22T02:38:47.537Z
Stan Liou
<p>I often hear that nothing can escape a black hole because its &quot;escape velocity&quot; is greater than <em>c</em>. If that is accurate, what about the following? I know that the following has a lot of most likely impossible assumptions, but I'm trying to understand whether the escape velocity explanation makes sense.</p>
<p>Suppose you've got some sort of space ship that's inside the event horizon, and it hasn't been destroyed by the gravity or tidal forces. Also suppose that you've got a whole lot of reaction mass and a fantastic power supply.</p>
<p>Could this space ship, through applying enough constant force escape the event horizon?</p>

<black-hole>
Escaping a black hole
Mitchell Kaplan
# Escaping a black hole

(Asked by: username_0 on 2013-11-25)

I often hear that nothing can escape a black hole because its "escape velocity" is greater than *c*. If that is accurate, what about the following? I know that the following has a lot of most likely impossible assumptions, but I'm trying to understand whether the escape velocity explanation makes sense.

Suppose you've got some sort of space ship that's inside the event horizon, and it hasn't been destroyed by the gravity or tidal forces. Also suppose that you've got a whole lot of reaction mass and a fantastic power supply.

Could this space ship, through applying enough constant force escape the event horizon?

**Tags:** black-hole


---

## 3 answers

### Answer by username_9 on 2013-12-22. Score: 22 | Accepted answer

One of the clearest way to see what's going on is to look at a Penrose diagram of a Schwarzschild black hole. A Penrose diagram is like a map of the spacetime drawn in such a way as to preserve angles and put the light rays diagonally at $45^\circ$ angles, forming the light cones.

Since we're mapping all of an infinite space(time) into a finite drawing, distances are necessarily distorted, but that's a small price to pay.

![Schwarzschild causal diagram, original by Andrew Hamilton](https://i.sstatic.net/UwOxF.gif)

Time goes up on the diagram, and a typical infalling trajectory is in blue.

Because every massive object must be locally slower than light, it must stay within those light cones. Hence, no matter how you accelerate, at every point of your trajectory you must go in a direction that stays within those $45^\circ$ diagonals at that point. But once you're inside the horizon, every direction that stays within the light cones leads to the singularity.

Accelerating this way or that just means that you get to choose where you hit the singularity--a little on the left on the diagram or a little to the right. Trying to escape using high acceleration brings you closer to the light's $45^\circ$ lines, which because of time dilation will actually *shorten* your lifespan. You'll actually get to the singularity *sooner* if you struggle in that manner.

This particular image came from Prof. [Andrew Hamilton](http://casa.colorado.edu/~ajsh/home.html). Note that it pictures an *eternal* Schwarzschild black hole, i.e. one that has always and will exist. An actual black hole is formed by stellar collapse and will eventually evaporate, so its diagram will be slightly different (in particular, there will be no "antihorizon"). However, in all respects relevant here, it's the same situation.

> **Comments:**
> **username_10**: Could you elaborate on how it's "the same situation" despite the black hole eventually evaporating, given that the singularity itself seems to actually reside an infinite time in the future, according to the diagram? (or at least according one understandable, though potentially naive, interpretation of the diagram)  

---

### Answer by username_1 on 2013-11-25. Score: 4

This is more of a physics question than it is astronomy, but nevertheless, think of it this way (most of what I say requires verification as I am not qualified to give a 100% correct in details answer): Light can't escape a black hole, and no propulsion system can accelerate an object to the speed of light. The faster you go, the more you weigh, the more force you have to input to maintain acceleration, the more energy you waste over time. If drawn on a graph, the energy required to increase speed by dX when at speed X, the graph has an asymptote at the speed of light. Meaning that it won't reach it no matter how much energy is input.

Take a look at LHC, where hadrons are accelerated to such a point when not their speed is measured anymore, because it hardly changes, but rather the energy of the particles, which increases a lot when approaching the speed of light. This will give you perspective about how unreachable it is.

So, if you can't accelerate to the speed of light then you, like light, are trapped inside the event horizon.

Also, AFAIK, light doesn't exit not because photons have weight, but because time stops. So light doesn't travel, nothing happens because there is no time.

Again, I'm not qualified. I just like to read about this stuff.

> **Comments:**
> **username_0**: My question revolves around my understanding that an escape velocity is an initial velocity, that without any additional acceleration is sufficient to escape the gravitational pull of a planet.  So, for example, if we had a good enough power source and reaction mass, we should be able to get arbitrarily far from the earth, while moving at a constant slow speed.  Correspondingly could this work with a black hole, or is there something about the curvature of space that makes escape impossible.  
> **username_1**: Like I've explained, you can't even reach the speed of light, and not even light can escape. There is nothing you could to to reach the speed of light. You need an infinite amount of energy to do this, which means in other words that it's impossible. Also, movement is described as a change in position in a time limit, and is defined by speed (t^-1), acceleration (t^-2) and higher level equations (t^-n), which are all dependent on time (t). Well beyond the event horizon there is no time, so "movement" doesn't make any sense as a concept.  
> **username_3**: Hmm, photons follow null geodesics of space-time. Why do you say that time stops? Also, what do you mean by this? Do you mean time as seen by an observer outside of the event horizon, or do you mean the local coordinate time of somebody who has fallen in. I think that part of your answer should be omitted.  
> **username_2**: There is not a lot that is relevant to the question here. Black holes are a General Relativistic phenomenon.  

---

### Answer by username_4 on 2013-11-26. Score: -5

Although I partially agree with @username_1ander here are a few more things.

According to Einstein's **special theory of relativity**, particles cannot travel at the speed of light (c). It would take infinite energy as stated above. However, the special theory of relativity states that an object can travel **slower or faster** than the speed of light but not at the speed of c. We may refer to the objects that travel faster than the speed of light as **tachyons**. There are celestial objects which are accelerated faster than the speed of light.

A common thing that everyone says is that nothing can escape a blackhole. But it is totally [wrong](http://www.space.com/16867-black-holes-quantum-mechanics-theory.html). Blackholes do emit particles and radiation called as **Hawking radiation**. Even stephen hawking has changed his mind about blackholes as the general concept that blackholes absorb everything can be disproved by quantum mechanics theories.

**So, If there exists a possibility that we can indeed escape a blackhole.**

At **CERN,** [reports](http://news.nationalgeographic.co.in/news/2011/09/110923-neutrinos-speed-of-light-particles-cern-physics-einstein-science/) says that **ghostly subatomic particles** called **neutrinos** were observed to travel faster than light. Researches are still trying to confirm it.

There is also another possible theory existing around the scientific community is the concept of wormholes. If a ship were trying to escape a blackhole, opening a wormhole to escape the blackhole and reaching another spot is a proposed theory.

There are also researches that say that objects are [emanated from blackhole](http://science.time.com/2012/10/04/how-to-escape-from-a-black-hole/).

> **Comments:**
> **username_0**: I think they've discovered an experimental error at CERN, something about the timing of the 2 clocks.  So they no longer think that the neutrinos may have traveled faster than light.  I think the things emanating from black holes are 1/2 of the virtual particle pairs that spontaneously appear in empty space, when a particular pair appears right outside the event horizon.  I'm wondering if you need to be moving anywhere near c to escape a black hole as long as you can apply continuous acceleration.  @username_1anderMP's comment about "time" may be my answer.  But I also wonder about curvature.  
> **username_4**: Although neutrino's have been proven wrong, the concept of tachyons still exist. One thing is for sure that there exists no element on earth to build a ship that can escape a blackhole even if we were able to harness the energy to do so. @MitchellKaplan  The **final results** were that neutrino speed were **equal to light**. The margin of error was 15ns.  
> **username_5**: @username_4 tachyons are not particles, they are instabilities, and the Hawking radiation arises not from the inside of the black hole but from the event horizon or slightly above.  
> **username_3**: @mahe, Where are you getting that special relativity says things can travel faster than the speed of light? This is completely incorrect. Also, neutrinos were not traveling at or faster than the speed of light once the connection error in the OPERA experiment was fixed. Neutrinos have mass - they do not travel at c.  
> **username_3**: Your comment about nothing escaping a blackhole is also misguided - see @username_5's response to it. Black holes are said to evaporate, but that doesn't mean that the things that were going in are now coming out (see Hawking Radiation - http://en.wikipedia.org/wiki/Hawking_radiation).  
> **username_6**: There's so much wrong with the answer, I don't even know where to begin. Please don't speculate, this is science, not a layman's guessing game.  
> **username_7**: Please improve this answer or it will continue to be down voted or even deleted.  
> **username_8**: The TIME article also is completely unhelpful. The original question was related to escape from inside the black hole, not from outside. And the error regarding Hawking radiation. . . oy.  

---

