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The most common explanation of what would happen to a space-ship that falls towards a black hole ends with spaghettification.

However imagine there was a space-ship built out of unobtanium, that could provide enough artificial gravity to counter-act the effects of the black hole on the ship's contents. As the ship is falling towards the hole, gravity is increasing, which in turn slows down the relative passage of time. Eventually billions of years pass "on the outside" and the black hole evaporates through Hawking radiation, which reduces the event horizon and allows the ship to escape.

Could this scenario be used to allow a hypothetical astronaut to travel billions of years into the future in the duration of a regular human life?

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    $\begingroup$ If the effects of falling into it can be counteracted then it is not a black hole, by definition. This is exactly the kind of premiss which contains its own negation. $\endgroup$
    – AlexP
    Commented Nov 30, 2016 at 13:55
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    $\begingroup$ @AlexP couldn't a sufficiently strong material withstand being inside the event horizon? $\endgroup$ Commented Nov 30, 2016 at 13:59
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    $\begingroup$ The event horizon is the place where the direction towards the black hole becomes timelike, that is, the direction towards the black hole becomes the future and the direction away from the black hole becomes the past. Locally the event horizon is nothing special; the only problem is that when an object is inside the event horizon it cannot escape, because the direction away from the black hole is in it's past. $\endgroup$
    – AlexP
    Commented Nov 30, 2016 at 14:06
  • $\begingroup$ I think you might be able to avoid some of AlexP's arguments by rewording. "Falling into a black hole" typically means you passed the event horizon, which even Stephen Hawking considers to be a one way trip if you want to call yourself "human" on the way out. It sounds like you just want to get very near the event horizon. This is a more tractable problem because it lets our space-ship remain in a region of space-time that's much easier to work out the math on. However, you will need something like anti-gravity, and the implications of that are.. odd. $\endgroup$
    – Cort Ammon
    Commented Nov 30, 2016 at 14:20
  • $\begingroup$ I'll give u the benefit of doubt and say everything goes according to ur plan, billions and billions of years later assuming the black hole do evaporate wouldn't that leaves nothing... $\endgroup$
    – user6760
    Commented Nov 30, 2016 at 14:21

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Here's the thing about spaghettification: there's nothing your ship can do to protect you.

The problem is that spaghettification is caused due to the fact that, near a strong gravitational force, the difference in distance between your feet and the gravitational source and the distance between your head and that gravitational source actually starts to matter. There's an r^2 term in gravitational forces. Your feet will feel a higher acceleration than your head will.

Which means the concept of free-fall breaks down. Your feet will constantly want to accelerate faster than your head will. It is this effect that tears your body to ribbons. It doesn't matter if the spaceship is made of adamantium or unobtanioum, because this effect passes right through it.

To do what you want, you need a source of anti-gravity that is tuned correctly to oppose this effect, or some anti-gravity shielding. Unfortunately, the closer you get to the black hole, the more anti-gravity you have to tune up. Anti-gravity doesn't exist, so science doesn't actually know what it would behave like, but it's reasonable to assume it would cancel out the relativistic gravitational effects as well, so the affected region would find time passes like normal. It probably wouldn't slow down like you want.

If you were try to push this to an extreme, passing through the event horizon, we'd have to sit down and really nail down the math you want for anti-gravity. We'd have to do it at the college physics/general relativity level, and it would be difficult. You'd have lots of infinities and infinitesimals creeping in which would take a lot of work to nail down. And, in the end, my conjecture would be that you'd still find time didn't slow down for you, even after that virtually infinite amount of effort.

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    $\begingroup$ Successfully calculating all of that sounds very improbable. I wonder if we could start by figuring out exactly how improbable it is? $\endgroup$ Commented Nov 30, 2016 at 14:56
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    $\begingroup$ I believe the question assumes that the ship can use antigravity, it is even made of unobtainium. Your answer assumes real life, but the question has already thrown that out the window. $\endgroup$
    – Ryan
    Commented Nov 30, 2016 at 16:53
  • $\begingroup$ You don't want to eliminate gravity. You want to level it out across the volume of the ship. This puts it in the same class as Star Trek inertial dampeners. $\endgroup$ Commented Nov 20, 2023 at 16:42
  • $\begingroup$ Robert Forward, Dragon's Egg. Super-dense masses orbiting around the ship to generate an opposing force to the tides. Of course the masses are handwaved but he was usually careful with his physics so I would assume the numbers worked. That wouldn't work against a black hole, though. $\endgroup$ Commented Nov 21, 2023 at 5:04
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Unfortunately, no.

Singularity and event horizon are two entirely different things. Event horizon determines the point...er... surface of no return. Singularity is where time (apparently) stops, and, unfortunately, singularity is just a point right in the middle of the black hole.

And, it's not enough to be just inside the black hole: you need to be very very close to the singularity to get what you want.

This poses two impossible problems:

  1. Near the singularity, everything falling into the black hole creates enormous pressure and will bombard your ship to oblivion if the ship could stay still. It's possible that even the light that the black hole is absorbing will pose such problem. Not to talk about interstellar medium, or rocks and asteroids and bigger chunks of matter that the black hole will be devouring.
  2. Time dilation effects depend on gravity, so you need the gravity to be constant across the whole astronaut. However, in case of a point, and at required proximity, even tiny differences in distance can make a difference of million years. Your astronaut would be aging so unevenly that they simply cannot survive even if they somehow could avoid the borbadment and spaghettification.
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    $\begingroup$ Good point about the temporal skew. Hopefully, averaging out the gravitational pull to eliminate spaghettification will also fix that. $\endgroup$ Commented Nov 20, 2023 at 16:28
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The fundamental problem here is that the event horizon isn't simply a one-way gate, but a transition in the nature of spacetime itself. Once you are below it you inevitably descend (just as we inevitably move forward in time) towards the singularity and go splat.

Furthermore, beware that just about every use of a black hole in science fiction that I'm aware of portrays them radically wrong. Your clock is still running at 1/3 of normal when you hit the photon sphere--and there can be no stable orbit below that.

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Yes, absolutely, with a little adjustment.

Just to clarify, if you want actual physics, there is no "falling into" a black hole. You can approach one, but time dilation will increase exponentially as you approach it. The Orville totally screwed this up. This is also true of the star itself. Event horizons don't actually form. An event horizon is mathematically identical to "matter exceeding the speed of light."

You don't want to counteract gravity itself. That's what's shortening the distance between the person and the future. You want to level out its effects so that the tidal forces don't rip you apart. It makes about as much sense as inertial dampeners.

Get into orbit around the black hole so that your orbital velocity both counters the pull and increases your temporal velocity. You'll want to do this with a super-massive black hole because the gradients aren't as bad as with smaller ones.

While you're at it, you'll need an ungodly amount of X-ray protection. Think in terms of "staring down the barrel of your enemy's spinal-mount cannon" kind of protection. You might manage this if you put yourself at the center of a planetoid, but it's too late at night for that kind of math.

So, slight update. There appears to be a misconception that, because the people in the spaceship perceive time at a slower rate, that they stay in the same time period. That's not the way it works. It's more of a stretching thing than a motion thing.

If you could stretch ten feet of rubber to reach a million feet, there would still be a 1 to 1 correspondence with an actual million foot long piece of rubber. It isn't like the end of the original piece of rubber is still only ten feet from the starting point.

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  • $\begingroup$ That is just wrong. Falling into a black hole would not allow you to see the far future due to redshift and light aberration. $\endgroup$
    – ErikHall
    Commented Nov 20, 2023 at 1:54
  • $\begingroup$ @ErikHall, You wouldn't "see" the far future, you would go there due to time dilation. Being in a strong gravitational field is identical to traveling at relativistic velocities. $\endgroup$ Commented Nov 20, 2023 at 16:24
  • $\begingroup$ This is the closest thing to an answer that actually takes into consideration the fact that the OP HAS A SPACESHIP THAT COUNTERS THE EFFECTS OF THE BLACK HOLE. By this I mean that WB.SE is a forum that seeks solutions that may be based in science as we currently understand it, but is not necessarily bound by those limitations. Unless the querent specifies that she wishes all solutions to be so bound. $\endgroup$
    – elemtilas
    Commented Nov 21, 2023 at 19:31
  • $\begingroup$ @elemtilas, OP specifically states, "As the ship is falling towards the hole, gravity is increasing, which in turn slows down the relative passage of time." Therefore it does not counter all of the effects of a black hole. He also specifies that the ship "counter-act the effects of the black hole on the ship's contents" This creates the situation "physics.stackexchange.com/questions/229888/…". Thank you for clarifying that you are downvoting without understanding either the question or the answer. $\endgroup$ Commented Nov 21, 2023 at 20:38
  • $\begingroup$ @elemtilas, My sincere apologies. You're right, I'm being over-sensitive. I saw the downvote combined with the comment and misread the comment. Dealing with argumentative people elsewhere on the forum has colored my perceptions, causing me to misattribute where the attack was coming from. I owe you one. $\endgroup$ Commented Nov 21, 2023 at 23:17
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You can never escape a black hole even if you could get enough anti gravity to cross back over the event horizon. This is because the black holes gravity is so strong it has bend spacetime back on its self so in theory you would just be going back in time and space within the loop till you came back round to we're you started always within the black hole. Easy way to see it is to roll a piece of paper in to a cylinder til the top and bottom of the paper are touching so if you start from the top of the paper and make your way around to the bottom of the paper your back were you started in space. And time isn't even relevant at this point for you because you will never cross back over the event horizon. And dont even get me started on the velocity problem with the front of your ship going faster than the back causing it to tear and stretch in to tiny little atoms or even quarks so just forget time travel what's in a black hole is destruction right down to creation it's self sorry

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  • $\begingroup$ Hi Chris! I think perhaps this would be better suited as a comment, because it doesn't actually address the question at all. The question assumes the existence of a space ship that counters the black hole's effects. It's not our job as querents to poo-poo the idea as impossible. Let the folks over on physics.se do that job! No, our job here as respondents is take the question asked, consider the parameters set, understand that this is a fictional world with fictional science that real world science is at odds with and then provide a solution to the worldbuilding problem! $\endgroup$
    – elemtilas
    Commented Nov 21, 2023 at 19:21
  • $\begingroup$ I'm sorry I totally misunderstood. The question is obviously theoretical and so I should of gave an equal answer I do apologise didn't mean to come across argumentative. Thank you for the clarification. $\endgroup$ Commented Nov 22, 2023 at 20:55

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