4 ms·

I can't accelerate towards next week, but I can predict when next week will happen, with extreme accuracy. Is this the same for reaching the singularity? Does t

I can't accelerate towards next week, but I can predict when next week will happen, with extreme accuracy. Is this the same for reaching the singularity? Does the person falling (for the sake of this example let's assume they maintain consciousness) experience the passing of time as they fall further "into" the black hole? If so, how long would one experiencing the falling until they reach the singularity?

jleahy 3y ago
Yes, and you can calculate exactly how much time it takes (it was an exam question in my final exams for undergrad iirc). The amount of time depends on the mass of the black hole but it's definitely less than a minute.
- ben_w 3y ago
  I'd always assumed that for TON 618 it would've been a few days… but I don't have a physics degree, and now I come to write this comment realise I'd been just presuming it was "Schwarzschild radius/c" and it's not necessarily going to be such an easy result.
russdill 3y ago
You certainly can accelerate to next week as measured by Earth calendars. Climb into your local particle accelerator and ask them to get you accelerating around the loop as close to the speed of light as possible. By accelerating, you can get to next week in just a few seconds of your own subjective time. Also, you can accelerate towards the black hole singularity and get there faster.
didgeoridoo 3y ago
I’d love to understand the interaction effects between 1) acceleration toward singularity (prob approaching c?), 2) gravity (prob approaching infinity?), 3) distance compression experienced by infalling observer. My instinct is that the observer would subjectively experience it to take exactly the time predicted by classical mechanics to “hit” the singularity — basically that all the considerations above would cancel out in the local reference frame — but that to an outside observer it would take an infinite amount of time.
- denton-scratch 3y ago
  That's my layman's model.
- pdonis 3y ago
  > I’d love to understand the interaction effects between 1) acceleration toward singularity (prob approaching c?), 2) gravity (prob approaching infinity?), 3) distance compression experienced by infalling observer. None of these things are useful in the case under discussion. 1) is invalid--the singularity is a moment of time, not a place in space, and you aren't "accelerating towards" it. 2) is not well-defined inside the horizon (spacetime curvature is, and does increase without bound as you approach the singularity, but that's not quite the same as "gravity"). 3) is a special relativistic effect on others observing you; you yourself don't experience any "distance compression" regardless of your state of motion.
pdonis 3y ago
> I can't accelerate towards next week, but I can predict when next week will happen, with extreme accuracy. Is this the same for reaching the singularity? If you know the mass of the hole, yes, you can predict how much time will elapse on your clock between now and when you hit the singularity. > Does the person falling (for the sake of this example let's assume they maintain consciousness) experience the passing of time as they fall further "into" the black hole? Yes. > If so, how long would one experiencing the falling until they reach the singularity? A reasonable estimate for free-falling into a black hole is that the time to reach the singularity is the 3/2 power of the radial coordinate you are falling from, in units of the hole's Schwarzschild radius. If you are just crossing the hole's horizon, you are at the hole's Schwarzschild radius, so your time to reach the singularity from there would be that radius divided by the speed of light (to convert to time units instead of distance units). For a hole of 10 solar masses, for example, this time is about 100 microseconds (Schwarzschild radius of about 30 kilometers divided by the speed of light).
- rocqua 3y ago
  What happens to my speed as I reach (hit?) the singularity 0.1s after crossing the event horizon? Do I jolt to a halt, do I continue to accelerate? Do I keep a fixed speed, but never change position?
  - pdonis 3y ago
    > my speed There is no such thing. Speed is not absolute in relativity. You can only meaningfully talk about your speed relative to some particular object or observer, and then, strictly speaking, only when you and that object or observer meet (i.e., your worldlines cross). Similar remarks apply to all of your questions; they simply aren't meaningful.

jleahy 3y ago

Yes, and you can calculate exactly how much time it takes (it was an exam question in my final exams for undergrad iirc). The amount of time depends on the mass of the black hole but it's definitely less than a minute.

ben_w 3y ago
I'd always assumed that for TON 618 it would've been a few days… but I don't have a physics degree, and now I come to write this comment realise I'd been just presuming it was "Schwarzschild radius/c" and it's not necessarily going to be such an easy result.

russdill 3y ago

You certainly can accelerate to next week as measured by Earth calendars. Climb into your local particle accelerator and ask them to get you accelerating around the loop as close to the speed of light as possible. By accelerating, you can get to next week in just a few seconds of your own subjective time. Also, you can accelerate towards the black hole singularity and get there faster.

didgeoridoo 3y ago

I’d love to understand the interaction effects between 1) acceleration toward singularity (prob approaching c?), 2) gravity (prob approaching infinity?), 3) distance compression experienced by infalling observer. My instinct is that the observer would subjectively experience it to take exactly the time predicted by classical mechanics to “hit” the singularity — basically that all the considerations above would cancel out in the local reference frame — but that to an outside observer it would take an infinite amount of time.

denton-scratch 3y ago
That's my layman's model.
pdonis 3y ago
> I’d love to understand the interaction effects between 1) acceleration toward singularity (prob approaching c?), 2) gravity (prob approaching infinity?), 3) distance compression experienced by infalling observer. None of these things are useful in the case under discussion. 1) is invalid--the singularity is a moment of time, not a place in space, and you aren't "accelerating towards" it. 2) is not well-defined inside the horizon (spacetime curvature is, and does increase without bound as you approach the singularity, but that's not quite the same as "gravity"). 3) is a special relativistic effect on others observing you; you yourself don't experience any "distance compression" regardless of your state of motion.

pdonis 3y ago

> I can't accelerate towards next week, but I can predict when next week will happen, with extreme accuracy. Is this the same for reaching the singularity? If you know the mass of the hole, yes, you can predict how much time will elapse on your clock between now and when you hit the singularity. > Does the person falling (for the sake of this example let's assume they maintain consciousness) experience the passing of time as they fall further "into" the black hole? Yes. > If so, how long would one experiencing the falling until they reach the singularity? A reasonable estimate for free-falling into a black hole is that the time to reach the singularity is the 3/2 power of the radial coordinate you are falling from, in units of the hole's Schwarzschild radius. If you are just crossing the hole's horizon, you are at the hole's Schwarzschild radius, so your time to reach the singularity from there would be that radius divided by the speed of light (to convert to time units instead of distance units). For a hole of 10 solar masses, for example, this time is about 100 microseconds (Schwarzschild radius of about 30 kilometers divided by the speed of light).

rocqua 3y ago
What happens to my speed as I reach (hit?) the singularity 0.1s after crossing the event horizon? Do I jolt to a halt, do I continue to accelerate? Do I keep a fixed speed, but never change position?
- pdonis 3y ago
  > my speed There is no such thing. Speed is not absolute in relativity. You can only meaningfully talk about your speed relative to some particular object or observer, and then, strictly speaking, only when you and that object or observer meet (i.e., your worldlines cross). Similar remarks apply to all of your questions; they simply aren't meaningful.