Largely inspired by recently watching an episode of Star Trek: Strange New Worlds.
If the escape velocity at the event horizon of a black hole is the speed of light then could an FTL ship, which can travel faster than light, escape a black hole?
Of course, it would have to be a sufficiently large black hole that the ship and its contents would not be sphagettified upon approach, but there are black holes that large.
Could Starfleet send something into a black hole and the retrieve it using warp drive FTL?
Or am I misunderstanding and the escape velocity of a black hole isn’t the speed of light but instead would require infinite speed?
Since the writers never formalized, published, and peer-reviewed a monograph of the interaction of an event horizon and warp subspace fields, I don’t think there’s an answer apart from fanwanking and headcanon. Are you requesting that? Because your original question seems to be firmly seeking some kind of reality-grounded science-based definitive answer.
For one of the questions, this is the operative part - the event horizon is not a physical horizon but a line demarcating when the escape velocity crosses the light speed threshold.
For planets/moons/etc, we typically reference the escape velocity at the surface for obvious reasons. For Earth, this means 11.2 km/s (give or take) at sea level. But let’s say you wanted to hit escape velocity away from Earth by launching from the moon. You’re already well above the earth at that point and would need something closer to 2.4km/s. Of course, getting to the moon in the first place would require quite a bit of effort itself much less setting up and escaping the moon’s gravity, which is why there’s all sorts of debate about space elevators and using the moon as a launch platform for solar system exploration and so on.
So back to black holes, yes, inside the event horizon and closer to the singularity, the escape velocity can and should be greater than c
I would think the ship’s warp drive would give it the ability to pop in and out of a black hole, since it’s essentially trapped in a bubble that isolates it from its immediate environment.
Of course, it’d probably be a waste of time looking to “recover” things, since most would probably no longer exist in coherent form. But other ships with warp capability might. It would be like finding the Defiant in the Mirror Universe.
That would be an interesting concept to explore. An entire episode (or several) could be devoted to it.
And, more to the point of the OP, in The Orville, which is just Star Trek Lite, they did just this in one episode to hide from the bad guys. They slipped over the Event Horizon, and so were invisible, due to light not escaping. There were also time dilation effects shown as they were waiting. Once the bad guys left, they used their FTL system to leave the black hole.
I saw this exact question recently in Quora with an interesting answer from Raphael Chryslar, an Aerospace Engineer with the ESA:
Short answer: surprisingly no!
Long answer, it because inside the event hoirzon of a black hole, even though yes a warp drive can go faster than light, it still cannot escape it because of another reason: time curvature.
Once inside a black hole, space flows at the speed of time (relative to you inside the hole) - which means as long as you go forward in time (present to future), you’ll simultaneously move further towards the singularity - whether you want to or not, it’s literraly impossible to stay still inside the event horizon. Check out the penrose diagrams for a quick understanding of space-time graphs inside a black hole.
In fact the curvature of spacetime inside is much weirder and scarier than you think: it’s because all possible futures, directions and trajectories now lead towards the singularity; and trajectories leading away from the black hole back into the universe now point into the past.
Also your spaceship has sensitive instruments that are designed to detect the gradient of gravitation, so you can orient yourself. Your instruments should point towards the singularity, so that you can point your FTL warp drive in the opposite direction to escape, but you’re thwarted. The instruments instead say that the singularity lies in every possible direction you take, and you cannot find ANY direction that leads back towards the event horizon. Because of the mutilated curvature of space-time, the singularity ironically behaves like a sphere that shrinks evenly around you (like being trapped inside a giant steel bubble with spikes pointing towards you). Sadly your infinitely-accelerating warp drive is no longer of use to you, because there is no direction of which to point it. At the same time, you’ll feel a very weird sensation, which feels like moving or looking ‘downhill’ towards the singularity in all directions. You’ll also see an empty superblack void all around you, both singularity and event horizon unobservable.
In supermassive black holes, where tidal forces that reach the point of ripping apart atoms lies deep within the event horizon, the ‘spaghetification’ also goes weird, where instead of being stretched, its more like being blown up on the subatomic scale. In a nutshell, falling into a black hole is not just falling into a FTL waterfall, but also falling out of the universe into another one with different physics.
However IF your warp drive can not only warp space faster than light, but ALSO can go infinetely BACKWARDS in time, THEN you INDEED CAN ESCAPE a black hole.
IIRC Spock figured out that enough warp close to a massive body like a star or black hole will throw the ship backwards in time, and that it is a pretty standard manoeuvre (if discouraged by the time cops). So escaping from a black hole should not be a problem
Not only is the ‘warp propulsion’ technology of the various Star Trek franchise shows and movies not really explicable in any “reality-grounded science”, it isn’t even self-consistent, so trying do divine some explicable rules that are even internally logical, much less physically sensible, is essentially impossible.
As has been noted, the event horizon of a black hole is just the point at which ‘events’ that occur within that domain can no longer causally influence anything in the outside universe. There is nothing particularly special about it, and if you enter the event horizon of a sufficiently large black hole that there are not extreme gravitational gradients you won’t even notice that anything particularly interesting has happened unless you attempt to fly back out of it or send a message, in which case you’ll find that all trajectories just wrap around the hole because there is no geodesic path requiring less than infinite energy to escape outward (although even that may not be obvious from within the event horizon due to distortion of space-time and the time dilation with respect to the outside universe).
A vessel that is literally capable of moving through space-time at superluminal velocity could, in theory, have an escape trajectory from within the luminal event horizon of a black hole, although as the Quora response cited by @Dorjan notes, it would also have to be capable of moving backwards through time. Actually, a vessel that could move at superluminal velocity would literally also be capable of going backward in time by definition, but that creates another set of causal paradoxes on top of the difficulty of exceeding infinite energy in the local frame, which would result in all kinds of mathematical impossibilities.
If one is assuming that the Star Trek warp drive works on a mechanic that is akin to the hypothesized Alcubierre ‘Warp Drive’ where the vessel moves at sunlight speed through a detached ‘bubble’ of space-time which itself is propelled through the surrounding plenum at an arbitrary speed–which is at least technically consistent with Einstein gravity–then it is entirely plausible, provided that you can somehow generate enough negative energy to induce some kind of reversion in local gravity such that a geodesic path does lead outward. That this requires some kind of ‘exotic matter’ with negative energy density that, as far as we know, only exists as a mathematical construct with no direct evidence (although it is possible that whatever causes ‘dark energy’ could have these properties) is not at all a problem for science fictioneers who are used to pulling novel pseudo-physics out of their collective asses.
So to escape the blackhole you need to break warp 10, but then you turn into lizard things and mate with each other before the crew can turn you back into humans. Man, Voyager was the worst.
I think the thing we need to realize is that, if something like Warp Drive or some other means of FTL is possible, than our current understanding of physics is clearly incomplete. At that point, any analysis of “what would happen if…” are inherently flawed, since we’re basing that analysis on incomplete information.
So all our answers are inherently speculative, and so story writers are free to come up with their own speculations. So long as they are internally consistent, they can work for the story.
This. In a word, extrapolating the curvature of spacetime a one approaches the EH suggests that inside the black hole, space and time are so distorted that they’re switched such that the direction to the singularity is now timelike and in the future, while the opposite direction to escape the black hole points to the past.
Of course, one can also claim that the equations of SR suggest that FTL travel does, in fact, send you backwards in time, so this kind of discussion is just piling one kind of nonsense on top of another and has no basis in science.
Right. If special relativity is correct, then FTL is exactly equivalent to time travel. And SR is literally the most precisely tested theory in all of science. Though of course that doesn’t necessarily mean that we might someday find some necessary tweak to it.
Interestingly, there is nothing in any of what’s known of physics to prohibit either time travel or FTL. Usually, the impossibility of time travel is taken as axiomatic, which then (due to SR making them equivalent) would also make FTL impossible. But how it is that time travel is impossible, nobody can say.
