On the possibility of exploding a black hole

[DaTario]

Hi All

Considering the relativistic kinematic and mechanical effects of the high gravitational fields of a black hole on an explosive device of X megatons, equipped with a timer to explode in a terrestrial time T after pulling the trigger, would it be possible to send this device directly to a black hole of mass M and produce an explosion that would disqualify the massive set as a black hole?

 

[Vanadium 50]

No.

 

[FactChecker]

To expand a little, the forces, energy, and pressure of even a small black hole are unimaginable (to me at least). The bomb would be ripped apart down to its subatomic particles. Even our sun would turn it into plasma and a supermassive black hole has been found that is 17 billion times larger than our sun.
I, for one, am always amazed by the size of astronomical objects.

 

[Ibix]

In classical physics, a black hole is a region of spacetime that is causally disconnected from everything outside it. You therefore cannot destroy one. The end.

If black holes do not behave as classical relativity predicts, we believe they evaporate and eventually explode. Adding energy to them actually slows this process, so the bomb would be counter-productive.

 

[DaTario]

In classical physics, a black hole is a region of spacetime that is causally disconnected from everything outside it. You therefore cannot destroy one. The end.

Ok, but how this causal disconnection works, in the sense that we know that a massive body, after crossing the event horizon, will be part of the black hole and hence will increase its size? I mean, it seems that something of our world has caused something in the black hole's world. I know that time issues in the frontier (event horizon) tend to become more and more complex.

 

[Ibix]

Ok, but how this causal disconnection works

It's one way. You can drop stuff in, but nothing comes out. So you can drop bombs on it forever; they can't make the interior affect the exterior. So the black hole is there forever.

after crossing the event horizon

That is a very difficult thing to define. There is a last moment when you can no longer stop the body from falling in, even in principle, but there is no moment when you know absolutely that the thing has gone in.

and hence will increase its size?

The only way to measure the size of a black hole is through its gravity. The massive object dropped in will become indistinguishable from the black hole, while never certainly crossing the horizon. The maths for this is messy.

 

[DaTario]

The massive object dropped in will become indistinguishable from the black hole, while never certainly crossing the horizon. The maths for this is messy.

when you say it is messy do you mean that at least one member of our species can determine?

 

[Ibix]

when you say it is messy do you mean that at least one member of our species can determine?

There's no analytical solution for a realistic case. You need a large computer.

 

[FactChecker]

In addition to worrying about the mathematics, you should pay attention to the scale of things. The largest black hole we have discovered has a mass 17 billion times larger than our sun
CORRECTION: This is the fastest growing, but not the largest. Some have been discovered that are orders of magnitude larger.
and it absorbs a mass equivalent to our sun every day. That black hole would not be affected in the slightest by any bomb we could ever make.

Are you talking about a tiny black hole? They may be theoretically possible.

 

[jbriggs444]

equipped with a timer to explode in a terrestrial time T after pulling the trigger

If you are talking about a timer set to tick off 10 seconds (or whatever) of local proper time and then trigger the detonation, that is quite simple.

Presumably you require that we compute the required timer setting. A quick Google search says that for a solar mass black hole it takes about six microseconds to pass from the event horizon to the end of the trajectory at the singularity. So our calculation can have about six microseconds of sloppiness in it.

"Proper time" is not "terrestrial time". To have a "terrestrial time" inside a black hole, one must first establish a simultaneity convention. The choice of convention is arbitrary and has no physical consequences.

Specifying a "terrestrial time" of detonation without specifying a simultaneity convention is meaningless.

 

[Vanadium 50]

You are all getting lost in the weeds. One cannot shrink a black hole by feeding it. Full stop.

 

[DaveC426913]

Not to mention that fact the definition of the event horizon is that - below it - nothing can escape.

Not light, not radiation, not fission byproducts, not fast moving beta particles. Certainly not a mere bomb.

They all pale in comparison to the steeply sloped curvature of spacetime.

 

[phinds]

In addition to worrying about the mathematics, you should pay attention to the scale of things. The largest black hole we have discovered has a mass 17 billion times larger than our sun and it absorbs a mass equivalent to our sun every day. That black hole would not be affected in the slightest by any bomb we could ever make.

My understanding is that 17 billion M is nowhere near the largest discovered. The link you provided did not see contain any statement saying that it is the largest as you claim, just that it is the fastest growing. I seem to recall having read about one that is about 30+ billion M and here's one that is 66 billion M

https://www.sciencefocus.com/space/black-hole-mystery

EDIT: Here's a list of big ones.

https://en.wikipedia.org/wiki/List_of_most_massive_black_holes

 

[FactChecker]

My understanding is that 17 billion M is nowhere near the largest discovered. The link you provided did not see contain any statement saying that it is the largest as you claim, just that it is the fastest growing.

I stand corrected. Thanks.

I seem to recall having read about one that is about 30+ billion M and here's one that is 66 billion M

https://www.sciencefocus.com/space/black-hole-mystery

EDIT: Here's a list of big ones.

https://en.wikipedia.org/wiki/List_of_most_massive_black_holes

Wow!

 

[DaTario]

You are all getting lost in the weeds. One cannot shrink a black hole by feeding it. Full stop.

But in physical terms, when a massive system (with the possibility of internal explosion reactions) approaches another massive system characterized by being a black hole, the condition is established to treat the problem as a collision (clearly I am not saying that the formalism should be Newtonian). The question would then be the following: How does the collision or scattering of a black hole (possibly small, with mass $M_{bh}$) occur when faced with the incidence of the following systems

a) ordinary massive system, with mass $m < M_{bh}$

b) ordinary massive system, with mass $m < M_{bh}$ and potential for explosion after crossing the event horizon.

c) non-ordinary massive system, with mass $m \approx M_{bh}$ (not a black hole)

d) another black hole, with mass $m_{bh2} < M_{bh}$

e) another black hole, with mass $m_{bh2} > M_{bh}$

?

Is it possible, in some of these cases, that after the collision we have nothing which fits in the definition of a black hole?

Remark: the kinetic energy of these incident systems being also a parameter to be considered.

 

[PeterDonis]

Is it possible, in some of these cases, that after the collision we have nothing which fits in the definition of a black hole?

Same answer as post #2: no.

That answer is not going to change no matter how many times you repeat the question. Thread closed.