Can alien civilizations use black holes as energy? The theory, which has plagued the university for half a century, has recently been confirmed by scientists at the University of Glasgow. Although scientists previously thought the phenomenon was beyond the test of human engineering, the researchers used sound waves to experiment with it.
The idea of black holes as energy was raised in the 1970s episode of Doctor Who. In 1969, When British physicist Roger Penrose explored the properties of black holes, which were still in the theoretical stage, he discovered that black holes had a practical application — if you happen to be members of the super-advanced alien race.
Penrose’s theory is that if you lower an object to the outer part of the black hole’s event horizon, it must move at the speed of light to remain stationary. When it is lowered, it gets negative energy. Simply put, extraterrestrial life can “borrow” power from black holes.
The smart thing, Penrose argues, is that if the object is divided into two, half into the black hole and the other half recycled, the backstroke will cause the negative energy to be lost, and half of the recovered half will get energy from the rotation of the black hole. There is no doubt that a black hole involves fantastic projects, so only highly developed civilizations have a chance to complete such a project.
Led by Marion Cromb, a scientific team at the University of Glasgow’s School of Physics and Astronomy uses a bit of lateral thinking. They reasoned why we didn’t use distorted light, and with distorted sounds, it worked much less frequently, and around it could design an experiment that in fact we, mere humans, could also build.
What they do is set up a small ring speaker to create distorted sound waves. These sound waves are then aimed at a rotating sound absorber made of a foam disc. At the same time, the sound transmitter behind the disk measures the frequency and amplitude of sound waves passing through the disk at an increasingly fast speed to see if the rotating Doppler effect will match Penrose and Zeldovic’s theory.
The linear version of the Doppler effect is familiar to most people, as the tone of the ambulance alarm rises as it approaches the audience, but decreases as it drives away. It is rising because sound waves arrive at the listener more frequently as the ambulance approaches, and then less frequently as the ambulance passes.
The rotating Doppler effect is similar, but it is limited to a circular space. When measured from the angle of the rotating surface, the distorted sound wave changes its pitch. If the surface rotates fast enough, the sound frequency will do something very strange — it can change from a positive frequency to a negative frequency, and thus steal some energy from the surface rotation.
What we heard during the experiment was very special. As the rotation speed increases, the frequency of sound waves is being shifted to zero by Doppler. When the sound starts to pick up again, it is because the sound wave has shifted from the positive frequency to the negative frequency. These negative frequency waves are able to extract some of the energy from the rotating foam disk and become louder in the process — as Zel’dovich proposed in 1971.