Black holes...

[Boerseun]

Right, folks...

 

Being the dimwitted rural ignoramus that I am, I've got a few questions regarding black holes that needs some answerin':

 

1. A Black Hole is a singularity with mass. Let's take two black holes, one the mass of Earth, and one the mass of the Sun (whether Black Holes of these masses are possible or not is immaterial right now). If we define density as mass/volume, and being a singularity, a Black Hole's volume is zero, then density for all Black Holes should be the same - infinite. (Although you can't divide by zero. So, the singularity can't be a mathematical point - there must be volume of some sort. If not, then all Black Holesshould have the same effect on their surrounds - which they clearly don't do).
   
2. A Black Hole, being point-sized, will be ruled by Quantum Mechanics. In other words, it will jump around and tunnel about randomly, and could (theoretically, before I get banned for talking tripe on this here fine site) be wrapped with copper wire outside the event horizon to produce endless energy, seeing as it will cause massive induction, what with its QM size and enormous mass - and permanent QM bouncing around. Forget about Hawking radiation for a second, but if the Black Hole can cause induction it must lose energy somehow. In other words, mass. Is this possible? So - if it can cause induction, it must lose either mass, or the QM-bouncing should taper off. Which means that a Black Hole can lose mass in other ways apart from Hawking radiation.
   

Isn't it more likely (seeing as both 1 & 2 above includes the singularity as crucial to the argument) that either I have a serious misconception about the mathematical nature of a 'singularity', a Black Hole doesn't collapse to a singularity, or if it does, it isn't, in fact, doing the QM-shake rattle and roll? Or won't a QM-sized Black Hole cause induction?

 

Or is it being prevented from acting like similar-sized quantum particles by the geometry of its gravity well? In which case it won't tunnel, and act exclusively in the relativistic world?

 

Ponderous... really ponderous.

 

Any thoughts?

[Boerseun]

Coming to think of it, a Black Hole should start spinning faster and faster as it collapses - until the surface spins at 99.999etc. c. This, alone (apart from QM bouncing) should cause induction, if you could catch one of these critters and wrap it in copper wire outside the event horizon. But this induction would only make the rotation slow down, not make it lose mass.

 

Hmmmmmm.....:)

[Bo]

first of all: any gravitational object can mathematically (classically) be represented by a point particle. that doesn't mean that it realy is a point particle. but this does bring us to the unfortunate conclusion that point masses in general relativity can be represented by singularities in space-time. does this not mean that the density of a macroscopic object becomes infinite; since in the limiting process you also have to take the limit m->0.

 

now for your second point: you have to be very carefull here; since you apply ordinary quantum mechanics to a singularity in space time. This doesn't work for 2 reasons:

1) we don't really know what a 'singularity in spacetime' is. (physicly that is; mathematicly it is clear)

2) QM doesn't apply so straight forward to spacetime.

 

Furthermore your conclusion is somewhat strange, because real point-like particles don't really exist in in QM, because of the uncertainty; you have to talk about probabilities; and exactly the probability that describes a point particle doesn't experience tunneling.

 

I hope this clarifies things a bit...

 

Bo

[Qfwfq]

Further:

 

1) A singularity actually means that there is something such as a divide-by-zero limit. Anyway, electrons have so far exhibited no sign of spatial extension, unlike hadrons. Preumably all quarks and leptons are pointlike. This is a consideration unrelated to the spatial distribution in a given state.

 

2) All objects are ruled by QM. A more relevant factor than size is mass, the greater this is, the shorter the de Broglie length will typically be.

[CraigD]

… a Black Hole should start spinning faster and faster as it collapses - until the surface spins at 99.999etc. c. This, alone (apart from QM bouncing) should cause induction, if you could catch one of these critters and wrap it in copper wire outside the event horizon.

I believe previous posters have sufficiently lashed you for your flagrant and whimsical abuse of Quantum Mechanics :) so I’ll just pounce on this one item.

 

A black hole, by definition, has such a high escape velocity that not even photons can escape from a volume of space within their event horizon.

Like visible light, the magnetic force is mediated by photons.

So, you (almost, maybe – darn that quantum weirdness) can’t detect any magnetic field from within the event horizon of a black hole, regardless of what weirdness it’s really up to in there! :)

 

:) This is not to say that black holes wouldn’t make great power plants. Several bright theorists have suggested that, due to their tendency to boil most of the matter thrown their way into x-rays, etc, they might prove very efficient mass-energy converters for any civilization advanced enough to figure out how to utilize them.

[GAHD]

Just so we're all on the same page, a link ta pritty interesting paper:

Title: The quantum structure of black holes

Authors: Samir D. Mathur

Comments: Review article, 58 pages, 2 figures

 

Title: An improved estimate of black hole entropy in the quantum geometry approach

Authors: A. Ghosh, P. Mitra

Comments: 5 pages, LaTeX; references and remarks added

 

lots of math and fancy words, but it will help anyone who doesn't understand where it's coming from.

[Boerseun]

=

:) This is not to say that black holes wouldn’t make great power plants. Several bright theorists have suggested that, due to their tendency to boil most of the matter thrown their way into x-rays...

Yeah.

 

I apologize for my ignorance, as stated as the premise in my original post here.

 

BUT... (King size BUT)...

 

IF a black hole can make a power source of any size at all, it must be losing something. If you can wrap that sucker in copper wire (for the sake of the argument, of course), and it can actually cause induction, something is crossing the event horizon - not? If the event horizon is what I've understood it to be, then it won't be able to yield any energy at all...?

 

The only source of radiant energy here that we know of is Hawking radiation (to the best of my limited knowledge). Obviously testing for this would be kinda hard, but still - for a black hole to boil away through Hawking radiation is speculative at best, seeing as that will take a couple o' kazillion years as well.

 

Test:

 

Wrap a black hole in an insanely big stator packet - what's gonna happen? And, more importantly, why is whatever's happening, happening? And, if the black hole is indeed yielding energy, what's the black hole losing? It must be losing something, in the likes of either mass or rotational energy to make up for the energy output?

 

Regardless - I did state in my original post that the length of my greying beard is only superceeded by the sheer size of my ignorance, so be nice to an old farmer here, man - pleeze...

[GAHD]

It's not the hole itself you'd harness: it's the X-ray plume coming out of it's poles that you tap. Wrap the copper wire around THAT sucker and you've got nasty power.

[CraigD]

… IF a black hole can make a power source of any size at all, it must be losing something. …

I’ve failed to make myself understood. Scientifically valid proposals for “getting energy from a black hole” don’t actually propose to get energy from the black hole, but to use it’s ferocious gravity to get energy from outside matter one puts close to, but not through, its event horizon – in essence, to use the BH as a “super igniter” of ordinary matter, like a furnace is used to get energy from coal.

If you can wrap that sucker in copper wire (for the sake of the argument, of course), and it can actually cause induction, something is crossing the event horizon - not?

If it can, then yes, but…

If the event horizon is what I've understood it to be, then it won't be able to yield any energy at all...?

Correct. So, you shouldn’t be able to induce a current by placing a conductor near a black hole.

 

In the real universe, though, most of the black holes we know anything about are surrounded by accretions disks full of ionized matter, which should be whipping up intense if weird magnetic fields, so your generator scheme would likely work somewhat, but not due to anything happening within the event horizon.

The only source of radiant energy here that we know of is Hawking radiation …

Here’s the critical formula for Hawking radiation:

Power = K / Mass^2, where K is a constant you can calculate from the equation here if you’re so inclined.

 

Yes, I have the fraction right-side-up – the more massive the black hole, the less energy it radiates!

For a sun-size black hole, Power = 10^-28 watts = nearly nothing,

for an earth-sized one, P = 10^-17 watts = still nearly nothing,

but for a tiny, 1 kg one, P = 10^32 watts = about 1 million times the Sun’s total luminous output! Plug in good ‘ole E=M*c^2 and divide by P, and you get a time-to-evaporate for the 1 kg black hole of 10^-15 sec = hardly any time.

 

This is why little black holes are predicted to evaporate almost instantly, big ones to last essentially forever (10^67 years for a sun-size one)

 

So, for your electric generator around a sun or greater-size black hole in clean space, even if 100% of the Hawking radiation was in the magnetic range of the spectrum, you’d get no more than 10^-28 watts of power.

 

... Obviously testing for this would be kinda hard …

Hard, but maybe not experimentally impossible sometime in the foreseeable future. Several orders of magnitude improvement on the technology that allows us to compress matter enough to detonate an H-bomb might (wildly guessing at the numbers here) make it possible to actually create a mini black hole, like the 1 kg one above. If so, the resulting Hawking radiation should be pretty spectacular and distinct.

 

If we ever manage to get an instrument package anywhere near a black hole, it would be nifty to test these assumptions – there’s a good chance that much of what we know about black holes, including Hawking radiation, is quite wrong.

[goku]

ye know, scientists can theorise or imagine about black holes all they want, doesn't mean that any of it is true.

are there black holes? i don't know, neither does anybody else.

the walt disney movie was purty neat.

[cwes99_03]

I believe all these questions deal with the current theory on black holes. You are correct in surmising that no one to date has actually "seen" a black hole. No one has ever actually "seen" something get sucked beyond the event horizon. They simply base their theories on what they have seen, and that is nothing, where something massive (talking billions of solar masses) exists. They have also seen the effects of that mass on surrounding material.

 

I too am superbly deficient on knowledge of QM. However, I pose this bit of thought.

 

We can agree on the existence (according to theory) of an event horizon. Since no information can come out of that volume, thereby allowing us to know the existence of what things look like inside of that region, and beyond that region, time (in theory) no longer exists or is possibly reversed(?), would not the volume of the black hole be defined by the event horizon boundary?

 

We treat astronomical bodies as point masses all the time in physics, largely because we can't travel close enough to the actual midpoint to need to treat it any differently. Do we not treat a black hole in similar fashion? Traveling near the event horizon would be suicidal at worst, or at best a really big bungy ride for the extreme sporter who dares to try to escape the pull of the BH. So unless we are such a sporter, we don't need to know what's inside, just what's going on around the thing.

 

How does one tunnel through non-existent space time? Tunneling refers to the ability to travel between field-effect wells, but a black hole as defined is the mother of all wells, gravitational or otherwise. QM therefore as far as I understand it doesn't apply inside a black hole because of the boundary conditions, unless of course one were to hypothesize that there are wells within the well of the black hole, and the matter within the black hole still behaved under some guise of qm.

[cwes99_03]

Just a thought, and I'll place it here instead of as an edit. When I said up there reversed(?) i was refering to our frame of reference here on earth would imagine time to be reversed (relativity and all.)