In 1971, English mathematical physicist and Nobel Prize winner Roger Penrose proposed how energy could be extracted from a rotating black hole.
He argued that this could be done by building a suit of armor around the black hole’s accretion disk, where infalling matter is accelerated to nearly the speed of light, releasing energy in multiple wavelengths.
Since then, several researchers have suggested that advanced civilizations could use this method (the Penrose Process) to power their civilization and that this represents a technosignature we should look out for.
Examples include John M. Smart’s Transcension Hypothesis, a proposed solution to the Fermi paradox in which he suggested that advanced intelligence could migrate to the region around black holes to take advantage of available energy.
The latest comes from Harvard professor Avi Loeb, who in a recent paper proposed how advanced civilizations could rely on a ‘Black Hole Moon’ to power their home planet indefinitely. The way this black hole would illuminate the planet it orbits, he argues, would provide a potential technosignature for future SETI studies.
His latest article, “Illumination of a Planet by a Black Hole Moon as a Technological Signature,” recently appeared in the Research Notes of the American Astronomical Society (RNAAS).
In 1975, Stephen Hawking theorized that black holes emit photons, neutrinos and some larger particles – subsequently known as ‘Hawking Radiation’. Since then, proposals for using black holes as an energy source have generally fallen into one of two camps.
On the one hand, there is the possibility of harnessing the angular momentum of their accretion disks (the “Penrose process”) or capturing the heat and energy generated by their super-fast jets (perhaps in the form of a Dyson sphere ). On the other hand, there is the possibility of feeding matter to the black hole and harnessing the resulting Hawking radiation.
In his paper, Loeb proposes how an advanced civilization could rely on this latter process by designing a black hole that would orbit its home planet. This black hole would be very small, weighing only one hundred thousand tons (1011 g).
If nothing is done, this black hole would evaporate within a year and a half due to the emission of Hawking radiation. But as Loeb said Universe today via email it can be maintained by adding relatively small amounts of matter (2.2 kg; 4.85 lbs) per second. In return, it would provide an endless power supply:
“This black hole system is the most efficient engine I have ever thought of. The fuel is converted into energy with the perfect efficiency of 100%, because the mass that falls into the black hole eventually comes out as Hawking radiation. I haven’t seen this idea discussed before and had a “Eureka moment” when I realized it a few weeks ago. The only other method to convert mass into radiation with 100% efficiency is the destruction of matter and antimatter.”
As Loeb points out, the amount of antimatter required is beyond anything humanity can currently achieve. Since 1995, the particle colliders at CERN have managed to produce less than ten nanograms of antimatter, which is enough to power a 60-watt light bulb for four hours.
By comparison, Loeb’s proposed 1011 g black hole could continuously deliver 40 quadrillion (4015) watts.
“Global energy consumption is a few terra-Watts, ten thousand times less than the power supply of this black hole,” Loeb added. “The other advantage of this black hole engine is that it can use any form of matter as fuel. It could be trash. There is no better way to recycle waste than converting it into clean energy with 100% efficiency.”
Another advantage is that a black hole can use any form of matter as fuel, including the waste that civilization produces. In this regard, a black hole engine would solve the waste problems of an advanced civilization and in return provide an inexhaustible supply of energy.
Globally, people produce approximately 1.92 billion tons of waste every year, which has serious consequences for our environment. This would be enough to power a 1011 gram black hole engine for over 437 million years!
As to how such a feat could be accomplished, Loeb points to an earlier op-ed in which he theorized that a sufficiently advanced civilization could create a “baby universe” through quantum tunneling. While such a feat would be something that only a Type III civilization (or more advanced) could achieve, a black hole engine would be much simpler and perhaps something that a Type II civilization could achieve:
“This is the big challenge. The good news is that it is much easier to produce such a black hole than a baby universe. But each production line of a 1011 g black hole requires compressing matter or radiation to a mass density 60 orders of magnitude above the density of solid iron.
“The density of atomic nuclei or neutron stars is only 15 orders of magnitude above the fixed density. This was possible to achieve with a cosmic ray density of less than a femtosecond after the Big Bang.”
This was the subject of another recently written article by Loeb, in which he argued that, based on general relativity, black holes can be created from light.
But what’s most interesting about this proposed black hole engine is the way it could be detected light years away, making it a viable technosignature that would indicate the existence of an advanced civilization.
Like many proposed technosignatures, particularly Dyson Spheres and other megastructures, the existence of a black hole engine is speculative and theoretical. But as Freeman Dyson himself once said, whatever we can imagine (and if the physics is correct), a sufficiently advanced civilization may already have been created. Loeb said:
“The black hole’s engine could be discovered as a rogue planet, a rocky planet illuminated by a gamma-ray moon, with no stellar-mass companion.
“If we ever find evidence for such an engine, we must consider the possibility that the source was created or trapped as a primordial black hole by a highly advanced technological civilization. There is no better sign of technological innovation than creating a furnace from the curvature of spacetime in the form of a mini black hole.”
Source: www.universetoday.com
