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Author Topic: Black holes give off energy?  (Read 4965 times)

Offline realmswalker

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Black holes give off energy?
« on: 21/05/2005 03:52:25 »
correct?
well would it be possible for a planet that was orbiting a black hole to develop a form of life, using the hawkins energy as a basis (insteald of photons) for energy?


 

Offline DoctorBeaver

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Re: Black holes give off energy?
« Reply #1 on: 21/05/2005 23:23:16 »
Possibly - but would it be life that needed a wheelchair to move around? *really wishes he hadn't said that*

It wasn't me - a big boy did it & ran away
 

Offline daveshorts

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Re: Black holes give off energy?
« Reply #2 on: 22/05/2005 00:09:39 »
I think it would be a very low energy sort of life as by the time the hawking radiation has been redshifted climbing out of the black hole it will be pretty low energy.

There is loads of energy released by stuff falling into most black holes, I would have thought this would be a better energy source
 

Offline chimera

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Re: Black holes give off energy?
« Reply #3 on: 22/05/2005 10:32:06 »
quote:
Originally posted by DoctorBeaver

Possibly - but would it be life that needed a wheelchair to move around? *really wishes he hadn't said that*

It wasn't me - a big boy did it & ran away



Eth, that's just a little La Tourette-like creative hickup. Same brain area.
Shame on you and pardoned. (go read Slant by Greg Bear for penance, it features that phenomenon btw).

And intuitively correct, amazingly. Do not underestimate tidal energies around a black hole, or even a neutron star.

So if you're contemplating wheel-chair based life, best make the wheel-chairs very, very sturdy and more importantly: make them leak-proof. This could be one messy ride. :D

The living are the dead on holiday.  -- Maurice de Maeterlinck (1862-1949)
 

Offline gsmollin

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Re: Black holes give off energy?
« Reply #4 on: 22/05/2005 23:18:48 »
quote:
Originally posted by realmswalker

correct?
well would it be possible for a planet that was orbiting a black hole to develop a form of life, using the hawkins energy as a basis (insteald of photons) for energy?



No, the radiation from a black hole is not stable for billions of years as it is from a main-sequence star, unless you are referring to a stellar-mass black hole, and then it is stable, but nearly zero. Any black hole that radiates significant energy, say as much as our sun, would radiate faster and faster as it evaporated, and then it would explode.
 

Offline DoctorBeaver

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Re: Black holes give off energy?
« Reply #5 on: 23/05/2005 10:29:21 »
I've read a few Greg Bear books but not that 1. I'll check it out. 2 Bear books I really enjoyed, although I must admit the 1st nearly gave me nightmares, were about an alien race sending matter/anti-matter bombs out into the universe to destroy any planets with life on them as they considered them a potential threat, & the 2nd was about the search for that race. I think 1 of them was called "Anvil of Stars" or something like that. It was a long time ago that I read them.
 

Offline chimera

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Re: Black holes give off energy?
« Reply #6 on: 23/05/2005 11:06:43 »
Slant is cool. Actually, started rereading it myself after posting... it features the only-way-to-fly AI in my eyes, in the form of Roddy... he'll probably add to your nightmares.

Not all his work is equally good, I don't like some of the odd tangents he goes on with Darwin's Radio etc, it's interesting but he takes the 'deus ex machina' of 'hidden networks within bacteria/dna'-metaphor a bit too far. In Slant it's a more hybrid version, and I think you'll find it eerily convincing. Roddy's inventor btw is a woman, Seefa Schnee, who inflicted herself with a 'mild' dose of artificial La Tourette to boost her creativity. Just bites her hand at times when it gets a bit much. Nice touch, that...

Your 1st was Forge of God, 2nd was Anvil of Stars, then. Forge of God is indeed truly awesome, and pretty terrifying and convincing. Books on a similar scale of events and equally disturbing are Earth by David Brin and Mother of Storms by John Barnes. You'll love those, I guess.

Oh, on topic: Neutron Star is an oldie by Larry Niven in which he describes what tidal forces can do to ya orbiting one...

The living are the dead on holiday.  -- Maurice de Maeterlinck (1862-1949)
« Last Edit: 23/05/2005 11:16:36 by chimera »
 

Offline rosy

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Re: Black holes give off energy?
« Reply #7 on: 23/05/2005 12:00:31 »
quote:
Any black hole that radiates significant energy, say as much as our sun, would radiate faster and faster as it evaporated, and then it would explode.

Is this because so much mass is lost as energy that it's not dense enough to be a black hole any longer? Why does it explode?
 

Offline gsmollin

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Re: Black holes give off energy?
« Reply #8 on: 23/05/2005 17:07:30 »
The radiation is inversely related to the mass of the hole, and the radius of the event horizon. As the hole radiates, it loses mass according to E=mc^2. I don't have a number for the mass of a black hole that would be radiating at the same rate as our sun, but I infer that it would have a tiny mass, based on the results of other researchers. Since the radiation would be increasing as the mass shrinks, the hole will go through a critical point where it explodes.

Oh, you are asking for the mechanism for Hawking radiation. Well, that's been explained by others better than I could. In a nutshell, In quantum mechanics, the vacuum has rich properties, and is a place seething with virtual particles. These particles jump into existence when they can borrow enough "vacuum energy" to do it, but since the average value of the vacuum energy is near zero, the virtual particles must annhilihate and return the vacuum energy before they become real. If a source of energy is nearby, they may get enough energy to become real. The black hole is such a source. The event horizon curves space so strongly that virtual particles can form at the event horizon, and fall through it before they return to the vacuum. Then a real particle can form outside the event horizon from the energy that was released, and radiate away. I have left out lots of details, like conservation of charge, and a hundred other theoretical details. You can probably find lots of info if you search on Hawking radiation and black holes.
 

Offline DoctorBeaver

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Re: Black holes give off energy?
« Reply #9 on: 23/05/2005 18:02:19 »
quote:
Originally posted by chimera


Your 1st was Forge of God, 2nd was Anvil of Stars, then. Forge of God is indeed truly awesome, and pretty terrifying and convincing.


Thanks, they're the ones :)
 

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Re: Black holes give off energy?
« Reply #9 on: 23/05/2005 18:02:19 »

 

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