Researchers from the University of Glasgow's School of Physics and Astronomy have found a way to experimentally verify a 50-year-old theory about an alien civilisation’s possible exploitation of a black hole, according to a study published in Nature Physics.
In 1969, Roger Penrose proposed a theory that an advanced extra-terrestrial civilisation could generate energy through a black hole by putting an object in its ergosphere, the outer layer of a black hole’s event horizon. In this position, the object would have to move faster than the speed of light in order to remain still, while acquiring a negative energy at the same time.
Shortly after this, Soviet physicist Yakov Zel'dovich said that this theory could be tested using “twisted” light waves. However, Zel'dovich’s idea has remained just a theory since 1971 due to the technological challenges that his experiment posed.
Now, researchers from the University of Glasgow's School of Physics and Astronomy have suggested that twisting “acoustic waves” instead of light can be used in a lab setting to prove the theory. The researchers constructed a special system using a “small ring of speakers” that helped to create a twist in acoustic waves similar to what was proposed by the Soviet scientist.
“What we heard during our experiment was extraordinary. What's happening is that the frequency of the sound waves is being doppler-shifted to zero as the spin speed increases”, said Marion Cromb, the paper’s lead author, as quoted by Phys.org.
“When the sound starts back up again, it's because the waves have been shifted from a positive frequency to a negative frequency. Those negative-frequency waves are capable of taking some of the energy from the spinning foam disc, becoming louder in the process—just as Zel'dovich proposed in 1971”.
According to the scientists, they were “thrilled” to be able to verify a half-century-old theory about the generation of energy through a black hole in their lab in Scotland, which they said also opens up a lot of new opportunities for “scientific exploration”.