In 1969, a British physicist named Professor Roger Penrose theorized that energy could be generated from a black hole by lowering something into the black hole's outer layer.
The object lowered into the black hole's ergosphere would have to move more swiftly than the speed of light to keep still. Professor then speculated that the object would obtain negative energy in the extreme region of space.
By dropping the object into the black hole and splitting it into half with one piece falling inside, the other half would then gain energy derived from the black hole's rotation. However, the absolute extent of engineering challenge the renowned physicist suggested only advanced life forms, such as extraterrestrial beings, could achieve the task.
After a couple of years, another physicist named Dr. Yakov Zel'dovich proposed that the theory could be tried with a more feasible, earthbound experiment. Moreover, the Soviet scientists projected using "twisted" light waves.
By hitting the surface of a revolving metal cylinder spinning at just the right speed, they surmised that it would end up being reflected with added energy extracted from the cylinder's rotation.
The only problem was that Dr. Zel' dovich's concept was untestable because for it to work, the prospective metal cylinder would have to rotate at least a billion times a second. In a new study, researchers from the University of Glasgow's School of Physics and Astronomy have finally found a solution to test both physicists' theories.
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Sound Manipulation Instead of Light
Instead of manipulating light, the researchers have thought of twisting sound. They found that it would be easier to work within a lab since it possessed a much lower frequency source.
They built a system including a small ring of speakers to generate a twist in the sound waves somewhat like the twist in the light waves suggested by Dr. Zel'dovich. The twisted sound waves were then focused on a rotating sound absorber made from a foam disc.
A set of microphones behind the disc collected the sound from the speakers as it made its way through the disc. This then increased the speed of its spin steadily. Furthermore, to tell if Penrose and Zel' dovich's theories were accurate, the researchers were looking to hear an alteration in the amplitude and frequency of the sound waves as they passed through the disc.
Semicentennial Theory Proven
According to Marion Cromb, the lead author of the study, the linear version of the doppler can be compared to an ambulance siren im which its sound appears to rise as it comes closer to the listener but drops as it moves further away.
He explains how the rotational Doppler effect is similar but is confined to a circular space, much like a black hole. The twisted sound waves alter in pitch when measured from the viewpoint of the rotating surface.
In the findings of their paper, the amplitude they acquired was as much as 30 percent greater than the original sound from the speakers. Cromb described what they heard from the experiment as "extraordinary."
He points out that the frequency of the sound waves is Doppler-shifted to zero as the speed of the spin accelerates. When the sound starts again, it means the waves have been shifted from a positive to negative frequency.
Finally, he says that the negative-frequency waves are able to take some energy from the rotating foam disc becoming louder in the course, just like Zel'dovich projected in 1971. Professor Daniele Faccio, a co-author of the paper, says they are thrilled with their discovery and having proven a theory that was 50 years old.
The researchers are optimistic that their findings could be used in future research, probably with space studies in black holes and extraterrestrial life forms. The findings of their research were published in the journal Nature Physics on June 22, 2020.
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