In 1971, English mathematical physicist and Nobel Prize winner Roger Penrose proposed a way to extract energy from a spinning black hole.
He argued that this could be done by building a harness around the black hole's accretion disk, where infalling material would be accelerated to near the speed of airy, releasing energy in many wavelengths.
Since then, many researchers have suggested that advanced civilizations could operate this method (the Penrose Process) to power their civilizations and that this is a technosignature we should pay attention to.
An example is John M. Smart's transcendence hypothesis, a proposed solution to the Fermi paradox. The author assumes that advanced intelligence can migrate to the region surrounding black holes to operate the energy available there.
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 provide their home planet with energy indefinitely. The way this black hole would illuminate the planet it orbits would provide a potential technosignature for future SETI studies.
His latest paper, “Planetary Illumination by a Black Hole Moon as a Technological Signature,” was recently published in Research Notes of the American Astronomical Society (RNAAS).
In 1975, Stephen Hawking theorized that black holes emit photons, neutrinos, and some larger particles—since then known as “Hawking radiation.” Since then, proposals to operate black holes as an energy source have generally fallen into two camps.
On the one hand, there is the possibility of using the angular momentum of their accretion disks (the “Penrose Process”) or capturing the heat and energy produced by their hypervelocity jets (perhaps in the form of a Dyson Sphere). On the other hand, there is the possibility of feeding the black hole with matter and using the resulting Hawking Radiation.
In his paper, Loeb proposes how an advanced civilization could rely on this latter process by constructing a black hole that would orbit its parent planet. This black hole would be very miniature, weighing only one hundred thousand tons (1011 g).
If left unchecked, this black hole would have evaporated in just a year and a half by emitting Hawking radiation. But as Loeb said The universe today via email, it could be sustained by accumulating relatively miniature amounts of matter (2.2 kg; 4.85 lb) per second. In return, it would provide an infinite source of energy:
“This black hole system is the most efficient engine I've ever thought of. Fuel is converted to energy with perfect 100% efficiency because mass that falls into the black hole ultimately comes out as Hawking radiation. I haven't seen this idea discussed before and I had a 'eureka moment' when I realized it a few weeks ago. The only other way to convert mass to radiation with 100% efficiency is through matter-antimatter annihilation.”
As Loeb points out, the amount of antimatter needed exceeds anything humanity can currently achieve. Since 1995, CERN’s particle colliders have produced less than ten nanograms of antimatter, enough to power a 60-watt airy bulb for four hours.
By comparison, Loeb's proposed 1011 g black hole could continuously supply 40 quadrillion (4015) watts.
“The world’s energy consumption is a few terawatts, ten thousand times less than what powers 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 can be garbage. There’s no better way to recycle garbage than to turn it into clean energy with 100 percent efficiency.”
Another advantage is that a black hole can operate any form of matter as fuel, including the waste produced by a civilization. In this respect, a black hole engine would solve the waste problems of an advanced civilization while providing an inexhaustible source of energy.
Globally, humans produce about 1.92 billion metric tons (2.12 U.S. tons) of waste per year, which has a sedate impact on our environment. That's enough to power a 1011 g black hole engine for over 437 million years!
As for how such a feat could be accomplished, Loeb refers to a previous paper in which he theorized that a sufficiently advanced civilization could create a “young universe” via quantum tunneling. While such a feat would be something only a Type III (or more advanced) civilization could achieve, a black hole engine would be much simpler and could perhaps be designed by a Type II civilization:
“This is a huge challenge. The good news is that it's much easier to produce a black hole than a baby universe. But any 1011-g black hole production line requires compressing matter or radiation to a mass density that's 60 orders of magnitude greater than the density of solid iron.
“The density of atomic nuclei or neutron stars is only 15 orders of magnitude greater than that of a solid. This was possible with a cosmic ray density of less than a femtosecond after the Big Bang.”
This topic was recently addressed by Loeb in his paper, 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 fact that it could be detected from light-years away, which would make it a credible technosignature indicating the existence of an advanced civilization.
Like many proposed technosignatures, especially 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 engine may turn out to be a rocky planet illuminated by a gamma-ray moon that has no stellar-mass companion.
“If we ever find evidence of such an engine, we would have to consider the possibility that the source was created or trapped as a primordial black hole by a highly technologically advanced civilization. There is no better indicator of technological innovation than the creation of a space-time curvature furnace in the form of a miniature black hole.”
Source: www.universetoday.com
Image Source: Pixabay.com
