Black Hole Shenanighans

[cicatrix]

Wouldn't spagetification rip the stick apart? Or is that only deeper in the gravity well?

As I understand it, that close to a black hole gravity doesn't actually act as a point mass, but each part of the ship/you/stick that's closer to the black hole would suffer more gravity (as it's a gradient)

If you choose a BH big enough (i.e. supermassive) then the tidal forces near the event horizon would be minimal. It would still be quite a way down towards the singularity where the mass of your bottom part would greatly exceed the mass of the upper one and you would be spagettified.

You can jump in (or throw something in a black hole) and eventually you (or the object you've thrown) would pass the event horizon within a finite amount of time (in the time-frame of the object). But, you cannot see how the object passes the event horizon from outside - you would see the object more and more redshifted, more and more slowed down and then it will just 'dissolve'.

Now, the stick - the closer its end would be to the event horizon the heavier the tip would become... at some point (quite above the EH) the material it's made of would break BEFORE it crosses the EH.

[AngelLestat]

Not really, if you bungee jumped past the event horizon or stuck a pole in, your ship would be sucked in too, since it is a part of your ship at that time. As stated above, you wouldn't even be capable of seeing beyond the event horizon. You wouldn't even be capable of getting out anyhow, seeing how you would have to travel faster than the speed of light to escape the event horizon.

Just passing the event horizon would not lead you into another place entirely. Realize that the event horizon is only the point in which light does not escape. It's much like the edge of a shadow, where just beyond is not necessarily something "different". That would be far beyond this point, down into the steepest part of the singularity, or even at the base, where, if you were lucky (or unlucky) enough to survive the trip, you would see, possibly, a swirling ball of matter, created by the matter collected from the area around you.

Carl Sagan call, it said that you are not allowed to use his name in vain

The even horizon of a black hole is the edge of our unirverse. You crossed and our universe ends for that person.

http://newsoffice.mit.edu/2012/measuring-a-black-holes-event-horizon-0927

“Once objects fall through the event horizon, they’re lost forever. It’s an exit door from our universe. You walk through that door, you’re not coming back.â€Â

And I still believe that my pole example depending the size of the black hole is the most accurate, taking into account the amount of words that I use..

Even 16 billon light years away, that is another even horizon from our universe, a different edge that you never can reach, and if you do.. the universe you knew ends.

[cicatrix]

“Once objects fall through the event horizon, they’re lost forever. It’s an exit door from our universe. You walk through that door, you’re not coming back.â€Â

I would have argued if these words were said by someone else

This is all very poetic, but falling through the event horizon simply means certain death. In a certain metaphysical way it is, indeed, an exit from our universe, but not very different from getting killed in a car accident.

[AngelLestat]

you can survive, it depends on how big is the black hole.

But it also depends if general relativity predictions are correct.

[cicatrix]

you can survive, it depends on how big is the black hole.

But it also depends if general relativity predictions are correct.

No, you cannot, once inside, all possible trajectories would lead you towards the singularity where you will be torn apart.

[AngelLestat]

First, I was saying that you can survive to cross the even horizon.. I dint said nothing else..

But there is a possible trajectory entering by the poles which can lead to another universe.

The black hole size also may help in your chances to survive.

Edited February 14, 2015 by AngelLestat

[cicatrix]

You can survive crossing, yes, but depending of the size of the black hole, you wouldn't have all that much time left.

And, another universe talks are pure speculations.

[AngelLestat]

of course are speculations, the same goes for anything predicted on and beyond the event horizon.

General relativity is not the only theory that might have something to said in that zone.

[Sirrobert]

Now, the stick - the closer its end would be to the event horizon the heavier the tip would become... at some point (quite above the EH) the material it's made of would break BEFORE it crosses the EH.

Or ripped out of your hands I asume. But wouldn't that be a very small version of spagetification?

I would have argued if these words were said by someone else

This is all very poetic, but falling through the event horizon simply means certain death. In a certain metaphysical way it is, indeed, an exit from our universe, but not very different from getting killed in a car accident.

You're not just dead. Your atoms are lost to the rest of the universe. In a way, you could call that 'not in this universe anymore'

[WestAir]

I don't think having the CoM outside the EH will save particles that cross it from falling in. I could be wrong but I don't think it works that way.

[-Velocity-]

You can survive crossing, yes, but depending of the size of the black hole, you wouldn't have all that much time left.

And, another universe talks are pure speculations.

I wouldn't be so certain that we really know what goes on inside a black hole, or even at the event horizon. Astrophysicists certainly aren't certain.

A mass that has the mass of the entire observable universe has a Schwarzchild radius about equal to, or even exceeding, the radius of the visible universe. If you include dark energy and dark matter, then the mass of the universe is about 2.5x10^54 kg, which has a Schwarzchild radius (392 billion light-years) which is much greater than the radius of the observable universe. Even if you cut out dark energy, the Schwazchild radius is still greater than the size of the observable universe, though I am not sure which number is the "proper" number to use for the radius of the observable universe in this particular case. In case you didn't know, the Schwarzchild radius is the minimum radius that a massive object can be compressed to before it collapses into a black hole; it's also the radius of the event horizon.

An additional interesting thing to ponder- to escape the visible universe, you must travel faster than the speed of light.

Sound familiar?

Anyway, yea, we really don't know for certain what happens inside a black hole, or even so much at the event horizon. If an infalling clock supposedly stops at the event horizon, then is even really proper to talk about what happens inside a black hole? There is nothing happening from our point of view. Which does not seem possible to reconcile with our predictions that an infalling observer observes himself reaching the singularity in finite time, but that an external observer observes the infalling observer reach the singularity in infinite time while observing the black hole evaporate due to Hawking radiation in finite time!!!

So I wouldn't be so sure of what really "happens" in there. We shouldn't dismiss ideas that "sound crazy", because black holes themselves are pretty crazy, and we simply don't understand black holes yet as our laws of physics are not complete. In that light, it's certainly possible that black holes could somehow birth new universes. The idea that we- and the entire universe- are inside a black hole has been seriously suggested by theorists. As I said earlier, there are certain eerie similarities...

Edited February 14, 2015 by |Velocity|

[Warzouz]

COUNTER QUESTION:

What I wonder is, "Could the singularity 'convert' matter into energy and emit it from the black hole as radiation?" We already know that black holes emit incredible amounts of energy in jets at the poles, so was that, at one point, matter? Could the matter and energy in the black hole be emitted from the poles and "take" from the black hole to achieve escape velocity (and is this causing black holes to evaporate?)? Could this escaping light be traveling faster than the cosmic speed limit to do so?

As it has been said, massive black hole ejects matter which is not passed the horizon. It's swirling matter at relativist speed. Some of it is pushed away. When black hole become inactive, dure to lack o falling matter, this effect disappears.

On the other hand, there is the Hawking radiation. Stephen Hawking says that black hole can emit energy through tunneling. This leads to "Black Hole evaporation". This effect is negligeable for massive black hole, but could be quite powerful for micro black holes.

That could lead to powering ships. Some scientists says that would be far more easier and less dangerous than harvesting anti-matter.

http://en.wikipedia.org/wiki/Black_hole_starship

That could do some some nice KSP mod.

The trick is to create a black hole...

[cicatrix]

I wouldn't be so certain that we really know what goes on inside a black hole, or even at the event horizon. Astrophysicists certainly aren't certain.

A mass that has the mass of the entire observable universe has a Schwarzchild radius about equal to, or even exceeding, the radius of the visible universe. If you include dark energy and dark matter, then the mass of the universe is about 2.5x10^54 kg, which has a Schwarzchild radius (392 billion light-years) which is much greater than the radius of the observable universe. Even if you cut out dark energy, the Schwazchild radius is still greater than the size of the observable universe, though I am not sure which number is the "proper" number to use for the radius of the observable universe in this particular case. In case you didn't know, the Schwarzchild radius is the minimum radius that a massive object can be compressed to before it collapses into a black hole; it's also the radius of the event horizon.

An additional interesting thing to ponder- to escape the visible universe, you must travel faster than the speed of light.

Sound familiar?

The key word is OBSERVABLE universe (which does't mean it's the WHOLE universe).

[YNM]

If the universe's density is equal to critical density, then the universe sits more or less at the transition between being a black hole and not a black hole. Observations doesn't seriously gives any clue of a specific value of universe's density today, even those expressed in critical density - you can only choose a specific combination of curvature and density, not one of it.

[peadar1987]

Surely you'd just be able to put your stick in and pull it out again. So long as your COM was outside the event horizon, there would be no reason for the end of the stick to become trapped. Actually, if the event horizon is the point where the orbital velocity is the speed of light, surely you can still escape by thrusting directly upwards, if you have enough thrust and delta-V. You don't need to reach escape velocity if you can keep thrusting and supporting the weight of your craft.

[BlueCosmology]

Surely you'd just be able to put your stick in and pull it out again. So long as your COM was outside the event horizon, there would be no reason for the end of the stick to become trapped. Actually, if the event horizon is the point where the orbital velocity is the speed of light, surely you can still escape by thrusting directly upwards, if you have enough thrust and delta-V. You don't need to reach escape velocity if you can keep thrusting and supporting the weight of your craft.

That doesn't make any sense at all. By that logic nothing could get trapped in an event horizon because you could always consider it as a system with something else that has it's COM outside the blackhole.

Also the event horizon is not the point where the orbital velocity is the speed of light, that is further away (for a schwarzschild black hole it is 3/2 times the event horizon)

Once past the event horizon every direction in spacetime points towards the singularity of the blackhole, meaning any force you apply to it would just send it towards the singularity.

[K^2]

Surface gravity at the event horizon is infinite. Even if you somehow managed to hold on to an object whose extremity is just above, the tension would exceed absolutely any material strength.

[Teamwork]

Surely you'd just be able to put your stick in and pull it out again. So long as your COM was outside the event horizon, there would be no reason for the end of the stick to become trapped. Actually, if the event horizon is the point where the orbital velocity is the speed of light, surely you can still escape by thrusting directly upwards, if you have enough thrust and delta-V. You don't need to reach escape velocity if you can keep thrusting and supporting the weight of your craft.

The CM has nothing to do with it. What keeps the stick together is the EM forces in the stick itself which are carried by photons. Since light only travels at a constant pace, once the stick goes into the black hole (where the escape velocity exceeds that of light) it'll become trapped inside. You could probably still continue to lower the rope inside the event horizon but you won't ever be able to pull whatever fell into the hole out again, regardless of where the CM is.

Though more likely the rope would be shredded long before it got to the event horizon.

COUNTER QUESTION:

What I wonder is, "Could the singularity 'convert' matter into energy and emit it from the black hole as radiation?" We already know that black holes emit incredible amounts of energy in jets at the poles, so was that, at one point, matter? Could the matter and energy in the black hole be emitted from the poles and "take" from the black hole to achieve escape velocity (and is this causing black holes to evaporate?)? Could this escaping light be traveling faster than the cosmic speed limit to do so?

Though I'm not entirely sure on this, the mass that is "converted" into energy is actually the energy of matter going from falling into an infinite gravity well. As an object falls closer to BHs, it gains kinetic energy which is often converted into heat if this object rubs against another one. This has the tendency to form these very very very hot material disks that revolve around BHs that give off tons of energy, something like 40% of the mass of the matter consumed.

While I'm not really sure what causes matter to be excreted from the poles, (probably something to do with the way the angular momentum of the disk is excreted) I can tell you that the energy comes from the gravitation collapse of the material around the hole.

Edited April 22, 2015 by Teamwork

[Warzouz]

Surface gravity at the event horizon is infinite. Even if you somehow managed to hold on to an object whose extremity is just above, the tension would exceed absolutely any material strength.

The gravity is infinite near the singularity, not at the event horizon. The event horizon is just a visual effect of the escape velocity higher than speed of light. It can get higher, much higher than that. On a super massive black hole you could cross the EH without harm (yet...). gravity gradient is not a

If you'd cross the event horizon, you wouldn't notice it as it would always seems to be under you (light would go done, always). It's not a barrier.

But beside that, there is no point knowing what's below the even horizon. Information can't get out. So what ever is inside doesn't interfere with the outside. That's why black holes are described as the simplest known object. There is no chemistry, no radiation (well the Hawking radiation is some kind of paradox), only 3 parameters : mass, electric charge, angular momentum. On the other hand, if you want to describe a simple rock, you would have an incredible number of parameters. I'm not sure that science is able to "describe" a simple stone.

As for orbiting photons, they don't orbit on the event Horizon, but higher (1.5 event horizon radius)

[AngelLestat]

Warzouz: you fall in his trap.. K2 is an evil guy

You need to spent infinite energy if you dont want to fall in that point (event horizon).

[K^2]

The gravity is infinite near the singularity, not at the event horizon. The event horizon is just a visual effect of the escape velocity higher than speed of light. It can get higher, much higher than that. On a super massive black hole you could cross the EH without harm

Excellent example of why people should not talk about black holes if they do not understand anything about gravity.

An object in free fall can safely cross event horizon, as tidal gradient is finite in this case.

Surface gravity is defined as acceleration experienced by a static point at the surface. Showing that this value becomes infinite at event horizon is one of the most basic exercises in GR. Surface gravity is the relevant quantity if you wish to suspend or support something at fixed elevation.

Talking about "gravity" itself being finite or infinite is pointless. There is no such concept in GR, and classical gravity does not apply. The real quantities in GR are proper acceleration, which is zero in free fall, and tidal acceleration. Free fall acceleration is purely a frame-dependent quantity, and only happens to match surface gravity in nearly flat metrics, which event horizon is an extreme case of not being.

Please, refrain from commenting on these thing, especially to"correct" someone, if you have not had a most basic course in differential geometry or GR. That goes for a bunch of people here. This isn't like rocket formula where you can learn one equation and be an expert.