Imagine that an extraterrestrial civilization were able to use a black hole to generate energy . It is the theory that the British physicist Roger Penrose suggested in 1969 (the same year that man reached the Moon). More than 50 years later, a team of scientists from the University of Glasgow (United Kingdom) has been able to successfully verify this theory.
For decades, this theory that sounded like science fiction to many, was impossible to prove because we have no way to travel to a black hole, or even survive such a powerful trip. Thanks to the experiment, which has been carried out with some modifications, scientists have been able to confirm this theory, which is published in the journal Nature Physics .
If you are wondering whether this study will help us generate energy here on Earth, the answer is no , but it is a fascinating illustration of a theory that seemed impossible to prove.
Sound instead of light
In essence, an object submerged at the outer limits of a black hole’s event horizon would carry negative energy, the authors explain. By cutting the loose object, some of that energy could be harvested as recoil.
To experimentally demonstrate the effect proposed by Penrose and, later, the physicist Yakov Zel’dovich (who suggested in 1971 to test the idea by bouncing twisted light waves off a cylinder that would have to rotate at 1,000 million times per second, a challenge of the all unsurpassed today), the researchers twisted sound instead of light, being a much lower frequency source and, therefore, more practical to be demonstrated in an environment such as a laboratory. They measured the Doppler effect of twisted sound waves bouncing off a spinning disk.
The sound waves were directed towards a rotating sound absorber made of a foam disc while various microphones picked up the sound from the speakers as it passed through the disc.
As they altered the pitch of the sound waves, the amplitude of the sound also increased , meaning that the sound waves borrowed energy from the disk much like the gravity-hanging object of a black hole.
“What we heard during our experiment was extraordinary. The waves changed from a positive frequency to a negative frequency. Those negative frequency waves are capable of taking some of the energy from the spinning foam disk, getting stronger in the process, just as as proposed by Zel’dovich in 1971 “.
It’s not about free electricity, physicists still need to power the spinning disk to get this effect, but it ‘s a long-awaited validation for a rather controversial theory.
“We are delighted to have been able to experimentally verify extremely strange physics half a century after the theory was first proposed. It is strange to think that we have been able to confirm a half century old theory with cosmic origins here in our laboratory in western West. Scotland, but we believe it will open up many new avenues of scientific exploration, “says study co-author Daniele Faccio.
Referencia: Marion Cromb et al. Amplification of waves from a rotating body, Nature Physics (2020). DOI: 10.1038/s41567-020-0944-3
