Can energy be sucked out of a black hole? Mathematical physicists propose making a “black hole bomb”! Rotating black holes have powerful natural forces that alter the space and space around them, so one wonders: Can black holes be some kind of source of energy? In 1969, mathematical physicist Roger Penrose proposed a way to achieve this goal, known as the Penrose Process.
Scientists have speculated that aliens or future humans could use this method to create “black hole bombs” to capture black hole energy, but some of the physics involved in the Penrose process have so far been untested. Currently, the recently published journal Nature Physics publishes some of the physics principles involved in the study.
Around the black hole horizon (the black hole boundary, nothing can escape the gravitational pull of the black hole, even light), the rotating black hole forms an area called the “energy layer”, where an object splits if it falls into the energy layer, one part falls into the black hole, and the other part escapes, and the escaped part effectively acquires energy at the cost of the black hole. So by firing objects or light into a rotating black hole, we can get energy.
But is this theory reliable? In 1971, Russian physicist Yakov Zeldovic thought of a black hole as some kind of rotating system and conducted simulation experiments on Earth, assuming that it was a rotating cylinder made up of energy-absorbing substances.
Zeldovic hypothesized that light waves could extract energy from the black hole cylinder and amplify them, and under the amplification effect, they required “angular momentum” to twist them into spiral structures.
When distorted light hits the cylinder of a black hole, the frequency of the distorted light changes due to the Doppler shift. When you hear an ambulance siren, it’s likely to feel this way, and when it’s close to you, it’s louder and the direction of movement changes the tone of the siren. Similarly, changes in the rotation speed of the black hole cylinder change the perceived frequency of light waves.
If the black hole cylinder rotates fast enough, the changed light wave frequency drops to a very low level, thus turning into a negative value, which means that the light wave rotates in the opposite direction.
Positive frequency light waves should be partially absorbed by the black hole cylinder and lose energy. But negative-frequency light waves convert energy loss into energy gain and are amplified by black hole cylinders, which extract energy from rotation, just as the black hole escape spent in Penrose’s theory.
Detecting Zeldovic’s theory may seem simple, but rotating objects need to keep light waves running at the same or higher frequency, and if they are to amplify visible light waves that oscillate at trillions of frequencies per second, they need an absorbent object that rotates billions of times faster than any mechanical device today.
The speed of light propagation is 300 million meters per second, and to make the theory easier to verify, the researchers chose to use sound waves, which travel a million times slower, meaning we don’t need the absorbents to rotate so fast.
To create distorted sound waves, the researchers used a ring of horns that emit the same frequency, but at slightly different start times, so the sound is spiralled. In the rotary absorbent experiment, they attach a sonic absorption foam to the motor, and after the foam interacts with the rotating absorbent, the microphone placed inside the foam can record audio.
We found that when the foam rotates more slowly (keeping the frequency low), the recorded sound is smaller because most of the sound is absorbed by the foam. But when we rotate the foam fast enough, close to the sonic frequency of the Doppler shift, the sound wave frequency becomes negative and its sound is loud.
The experiment only showed that sound waves could extract energy from rotating absorbents, finally validating the black hole theory of Russian physicist Yakov Zeldovic 50 years ago.
Black Hole Bomb
Of course, none of this fully proves that Penrose’s idea of energy acquisition really applies to black holes, but rather that our experiments prove the underlying physical view contrary to intuition, proving that light waves or sound waves are gaining energy, not lossing energy, in the process of shifting light waves or sonic frequencies from positive to negative.
Although we have not yet extracted energy in any area close to a rotating black hole, this does not mean that extraterrestrial intelligent civilizations or future humans with advanced technology can achieve this goal, perhaps some extraterrestrial intelligent civilizations build a structure around the black hole, which rotates with the black hole, and then throws asteroids and even electromagnetic waves into the black hole, which will eventually reflect out with more energy.
In addition, aliens can use a mirror shell to completely surround the black hole, thus creating a “black hole bomb”, the light that enters the black hole is magnified, and then reflected through the mirror to the black hole, amplified again, so looping.
The black hole’s energy grows exponentially before and after the escape explosion, but it is released by amplifying it through a hole that scientists can control in the process, essentially producing infinite amounts of energy.
Although this is only a scientific hypothesis, in the distant future, when the universe is dying and the remaining remaining debris of galaxies and stars is a black hole, this method is the only hope for any civilization to continue.