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Could we harness energy from black holes?:
A remarkable prediction of Einstein's theory of general relativity -- the theory that connects space, time and gravity -- is that rotating black holes have enormous amounts of energy available to be tapped.
[...] [Now] physicists Luca Comisso of Columbia University and Felipe Asenjo of the Universidad Adolfo Ibáñez in Chile have found a new way to extract energy from black holes by breaking and rejoining magnetic field lines near the event horizon, the point at which nothing, not even light, can escape a black hole's gravitational pull.
"Black holes are commonly surrounded by a hot 'soup' of plasma particles that carry a magnetic field," said Comisso. "Our theory shows that when magnetic field lines disconnect and reconnect in just the right way, they can accelerate plasma particles to negative energies, and large amounts of black hole energy can be extracted."
The U.S. National Science Foundation-funded research results could allow astronomers to better estimate the spin of black holes and possibly discover a source of energy for the needs of an advanced civilization, Comisso said.
[...] "Thousands or millions of years from now, humanity might be able to survive around a black hole without harnessing energy from stars," Comisso said. "It is essentially a technological problem. If we look at the physics, there is nothing that prevents it."
Journal Reference:
Luca Comisso, Felipe A. Asenjo. Magnetic reconnection as a mechanism for energy extraction from rotating black holes, Physical Review D (DOI: 10.1103/PhysRevD.103.023014)
(Score: 2) by Muad'Dave on Monday January 25 2021, @01:01PM (4 children)
I thought tiny black holes evaporated [briankoberlein.com].
(Score: 2) by Immerman on Monday January 25 2021, @02:45PM (3 children)
They do - but the smaller they are, the greater the power output, and thus the faster they lose mass. The tiny ones with atom-scale masses that might be produced at the LHC would evaporate instantly. But Phobos is still pretty massive - at ~10km across it's still a good sized mountain.
Try the calculator, it's fun to play with, just put in the mass and it'll tell you size, lifespan, luminosity(=power output), etc. in whatever units you want https://www.vttoth.com/CMS/physics-notes/311-hawking-radiation-calculator [vttoth.com]
Some examples around the tipping point:
Cruise ship (200e6kg): 7e15W, 32y
Olympic-sized swimming pool (2.5e6 kg): 5.7e19W, 22 minutes
40ft shipping container, filled to max (35e3kg): 3e23W, 3ms
Of course, that assumes both that we properly understand Hawking radiation, and that there is no other quantum weirdness that starts messing with black holes smaller than an atom.
(Score: 2) by Immerman on Monday January 25 2021, @03:04PM (2 children)
Oh, and just to put that power output in context:
That cruise ship would be putting out roughly 4x as much power as reaches the entire Earth from the sun.
The shipping container would be putting out almost 1/1000th of the sun's total power.
(Score: 2) by Muad'Dave on Tuesday January 26 2021, @12:32PM (1 child)
Thank you for your informative replies to my questions!
(Score: 2) by Immerman on Tuesday January 26 2021, @02:16PM
You're welcome. You got me curious as to where exactly the tipping point was.