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Falling into a super-massive Black Hole

JeanTate

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Imagine an isolated one, with no spin, and no net electric charge; imagine a super-duper massive one, with an event horizon (EH) 0.1 light-year in radius (yeah, unlikely there are many, if any, in the observable universe).

Imagine you are tiny, only 1mm top to tail, and that you have a set of extremely robust, highly precise and accurate, and equally tiny clocks and rulers, which you are able to carry with you right up to extreme spaghettification.

You cross the EH without noticing anything, as you can observe only your local environment, and tidal forces are immeasurably small here.

By your own clock, how long do you have to live, before you hit the singularity?

What about if the SMBH has a spin just a tad less than maximal? Would your remaining life be much longer? Shorter? Does it make a difference if you’re falling in at a pole? The equator?

What if both you and the SMBH are charged?
 
You could try this link:

bbc.com/earth/story/20150525-a-black-hole-would-clone-you
 
JeanTate said:
Imagine an isolated one, with no spin, and no net electric charge; imagine a super-duper massive one, with an event horizon (EH) 0.1 light-year in radius (yeah, unlikely there are many, if any, in the observable universe).

Imagine you are tiny, only 1mm top to tail, and that you have a set of extremely robust, highly precise and accurate, and equally tiny clocks and rulers, which you are able to carry with you right up to extreme spaghettification.

You cross the EH without noticing anything, as you can observe only your local environment, and tidal forces are immeasurably small here.

By your own clock, how long do you have to live, before you hit the singularity?

What about if the SMBH has a spin just a tad less than maximal? Would your remaining life be much longer? Shorter? Does it make a difference if you’re falling in at a pole? The equator?

What if both you and the SMBH are charged?
Click to expand...

Let's just say you will be truly unhappy but pretty much not for very long.
 
rjh01 said:
Interesting read. I always thought that if you fell into a black hole time would slow down so that you would watch the rest of the universe's life. All of this before falling in. This would mean that there is no two copies of you. But then I cannot find any article that agrees with me.
Click to expand...

Just draw a Penrose diagram of the black hole and it's easy to see that you won't see the entire future history of the universe before you hit the singularity.
 
If your eyes and brain were allowed to magically remain intact I think everything around you would freeze up.
 
Actually, I think the more interesting implication is that you'd be able to observe the parallel universe too, if there is one. For a short while, anyway.
 
Roboramma said:
Not quite sure what you mean by "freeze up" but, nope.
Click to expand...

Hmm, actually, I think I'm starting to understand what he meant. And as usual, please correct me if I'm wrong.

The thing is, you'll be accelerating FAST. In fact, acceleration rises asymptotically towards infinity as you approach the singularity. So your speed will basically asymptotically approach the speed of light.

Basically in that Penrose diagram, you'll always impact the singularity at 45 degrees. Basically if you draw your trajectory in that space, you have to enter at a relatively vertical-ish angle (time-like) or you'd be going faster than c. But from there it doesn't curve upwards towards the singularity as I've seen it drawn in many places, but curve to the left, to impact at 45 degrees.

Of course, the derivative dx/dt won't actually be c, i.e., 45 degrees, except in the actual point of impact, i.e., the singularity.

Well, it's hard to explain without drawing a picture, but I imagine you smart folks can draw a diagram in your head and know what I'm talking about.

What that means is that at that point a lightray is a tangent to your spacetime trajectory. As you approach the singularity, and draw those 45 degrees lies from the outside to your position for each second in your time, the distance between them gets smaller and smaller, until it is literally zero in the singularity. The time outside the black hole -- or for that matter inside the black hole -- effectively freezes up as observed by you.


Or in less fancy terms, just apply the time dilation from special relativity. As you approach the speed of light, you see everything else freezing up, because 1 second in the other frame takes years in yours.
 
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Lots of interesting things posted!

But how long will it take, as measured by my trusty clock, before I get within 1 km of the singularity, say?

And what difference does it make - if any - if the SMBH has maximal spin?

Numbers, equations, formulae please.
 
Frustration:

I've been reading about this black holes and what's supposed to happen if you fall into one for years, but I've never found a consistent scenario, except that you're on your way to the spaghetti factory. Especially confusing is how its supposed to look for your mate who doesn't cross the event horizon as opposed to you who do.

Google is not my friend here. It's a great resource of widely varying pop narrations. At least they are all more interesting than a Disney movie.
 
Oh, for your mate outside the event horizon, that's easy. For that one, you never cross the event horizon, much less reach the singularity.

You can pretty much draw the vertical axis to be time, the horizontal to be space, and draw a vertical line where the event horizon is. As seen by your friend, your trajectory will be asymptotic to that vertical line, but never cross it.

And since space behaves like that along a radius, you'd pretty much appear to get thinner and thinner, until you're a 1 planck length thick blob on the surface of the black hole.

Anything that ever fell into the black hole, and even matter that was always inside the event horizon to start with (e.g., matter exactly in the centre of a star whose core collapsed into a black hole), will appear to your friend outside the black hole to be plastered on the event horizon.


ETA: Well, any signal from you will also get increasingly red-shifted and weaker, so basically your friend wouldn't actually get to see you as a thin blob. More like you'd fade to black.
 
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HansMustermann said:
The thing is, you'll be accelerating FAST.
Click to expand...
Not really.

JeanTate said:
But how long will it take, as measured by my trusty clock, before I get within 1 km of the singularity, say?

And what difference does it make - if any - if the SMBH has maximal spin?

Numbers, equations, formulae please.
Click to expand...
It depends on the mass M of the black hole. And on your initial velocity.

According to the calculation in QUERY 2 of this draft chapter 7 for the second edition of Exploring Black Holes, by Edmund Bertschinger, Edwin F Taylor, & John Archibald Wheeler, the time it takes to fall from the event horizon to the central singularity is 4M/3 (in natural units). (Assuming, I believe that you started the fall "from infinity", which I won't try to explain here.)

I don't have time to check that right now, and it's been a while since I calculated the formula myself, but I can confirm from memory the fact that you live longer when falling into a more massive black hole than into a less massive black hole. The intuitive reason for that is that the more massive black holes have event horizons that are farther away from the central singularity.
 
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Jean Tate, make sure you take a bowl of spaghetti with you and tell me what happens.

Would it make really long spaghetti if some stayed on the outside of the event horizon, whilst some fell in?
 
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HansMustermann said:
Oh, for your mate outside the event horizon, that's easy. For that one, you never cross the event horizon, much less reach the singularity.

You can pretty much draw the vertical axis to be time, the horizontal to be space, and draw a vertical line where the event horizon is. As seen by your friend, your trajectory will be asymptotic to that vertical line, but never cross it.

And since space behaves like that along a radius, you'd pretty much appear to get thinner and thinner, until you're a 1 planck length thick blob on the surface of the black hole.

Anything that ever fell into the black hole, and even matter that was always inside the event horizon to start with (e.g., matter exactly in the centre of a star whose core collapsed into a black hole), will appear to your friend outside the black hole to be plastered on the event horizon.


ETA: Well, any signal from you will also get increasingly red-shifted and weaker, so basically your friend wouldn't actually get to see you as a thin blob. More like you'd fade to black.
Click to expand...

Sounds good: getting plastered, fade to black. Thanks. :wackysmile:
 
W.D.Clinger said:
Not really.


It depends on the mass M of the black hole. And on your initial velocity.

According to the calculation in QUERY 2 of this draft chapter 7 for the second edition of Exploring Black Holes, by Edmund Bertschinger, Edwin F Taylor, & John Archibald Wheeler, the time it takes to fall from the event horizon to the central singularity is 4M/3 (in natural units). (Assuming, I believe that you started the fall "from infinity", which I won't try to explain here.)

I don't have time to check that right now, and it's been a while since I calculated the formula myself, but I can confirm from memory the fact that you live longer when falling into a more massive black hole than into a less massive black hole. The intuitive reason for that is that the more massive black holes have event horizons that are farther away from the central singularity.
Click to expand...
Thanks very much! :)

Lots of good stuff in that link.

From Equation 4) if the SMBH has a mass of ~106 sols, I have not quite 7 seconds to live :jaw-dropp
 
Sol88 said:
Jean Tate, make sure you take a bowl of spaghetti with you and tell me what happens.
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Not any time soon, Sol88.

The nearest SMBH - SgrA* - is ~8 kpc away.

And if I fell in, you'd have to wait at least 100 billion years to receive anything I could try to tell you (i.e. for the SMBH to evaporate).

Would it make really long spaghetti if some stayed on the outside of the event horizon, whilst some fell in?
Click to expand...
Unfortunately, spaghetti is pretty soft, so it'd be ripped to atoms before your body would (but not by much). In fact, even spaghetti made of the toughest steel wouldn't remain in one piece for long at all.

Oh, and it's impossible for some to stay outside the EH and some to fall in (you know why, don't you?).
 
JeanTate said:
Not any time soon, Sol88.

The nearest SMBH - SgrA* - is ~8 kpc away.

And if I fell in, you'd have to wait at least 100 billion years to receive anything I could try to tell you (i.e. for the SMBH to evaporate).


Unfortunately, spaghetti is pretty soft, so it'd be ripped to atoms before your body would (but not by much). In fact, even spaghetti made of the toughest steel wouldn't remain in one piece for long at all.

Oh, and it's impossible for some to stay outside the EH and some to fall in (you know why, don't you?).
Click to expand...

Not really but i’m sure you could prove it with some very complicated mathamajics.
 
JeanTate said:
Not any time soon, Sol88.

The nearest SMBH - SgrA* - is ~8 kpc away.

And if I fell in, you'd have to wait at least 100 billion years to receive anything I could try to tell you (i.e. for the SMBH to evaporate).


Unfortunately, spaghetti is pretty soft, so it'd be ripped to atoms before your body would (but not by much). In fact, even spaghetti made of the toughest steel wouldn't remain in one piece for long at all.

Oh, and it's impossible for some to stay outside the EH and some to fall in (you know why, don't you?).
Click to expand...



I believe it would take much, much longer than that, since a 1 solar mass black hole takes roughly 10^67 years to evaporate.
 
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