A team of researchers claims to have verified a decades-old theory that energy can be created by black holes.
Scientists at the University of Glasgow School of Physics and Astronomy set out to validate Roger Penrose’s work in 1969. They used sound waves in an attempt to support “extremely strange physics half a century after the theory was first proposed. “
British physicist Penrose theorized that energy could be created by throwing objects like a rocket into a black hole and dividing the object in two. One half escapes the black hole, while the other falls beyond the point of no return (the ‘event horizon’).
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The escaping half steals a small amount of rotational energy from the black hole, which means it ends up with slightly more energy overall.
He theorized that energy could be stored and used to power entire worlds, but Penrose said the engineering challenge posed by the experiment could only be carried out by an advanced, possibly alien, civilization.
In 1971, physicist Yakov Zeldovich suggested that the theory could be tested with twisted light waves projected onto a rotating surface. To prove that, the rotating surface would need to rotate at least a billion times per second, a feat that is not yet possible due to engineering limitations.
Now, the Glasgow researchers have finally found a way to experimentally demonstrate the effect using sound waves, which require a much slower rotating surface.
Using a speaker ring, the researchers sent a rotating sound wave to a rotating foam disk. Two microphones were attached to the back of the disc, which they found that as sound waves passed through the disc, sounds were amplified by as much as 30 percent, known as the rotational Doppler effect.
Marion Cromb, lead author of the article, said: “The linear version of the Doppler effect is familiar to most people. The phenomenon occurs when the tone of an ambulance siren appears to rise as it approaches the listener, but falls as it departs.
“It seems to increase because the sound waves reach the listener more frequently as the ambulance approaches, and less frequently as it passes.”
The researcher added: “The rotational Doppler effect is similar, but the effect is limited to a circular space. Twisted sound waves change their pitch when measured from the point of view of the rotating surface.
“If the surface rotates fast enough, the frequency of sound can do something very strange: It can go from a positive frequency to a negative frequency, and in doing so, steal some energy from the rotation of the surface.”
During the experiment, the researchers discovered that when the sound wave hits the spinning disc, the pitch falls until it becomes too low to hear. Then, as it passed, the pitch rose again and the sound was amplified by up to 30 percent compared to the original sound.
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Professor Daniele Faccio, co-author of the article, said: “We are delighted to have been able to experimentally verify some 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 theory with cosmic origins here in our laboratory in western Scotland, but we believe that it will open up many new avenues of scientific exploration.”
“We believe it will open up many new avenues for scientific exploration. We are eager to see how we can investigate the effect on different sources, such as electromagnetic waves in the near future. “
Q&A Reader: Why does light travel faster than sound?
Asked by: Toby Graham, Shrewsbury
According to Einstein’s Special Relativity, the speed of light has a unique state: it is a fundamental characteristic of our Universe, which represents the maximum speed at which information can travel from one place to another. As such, nothing can match the 300,000 km / s achieved by light traveling through a vacuum, let alone sound, which being compression and expansion waves in a substance does not even exist in a vacuum.
That said, light can be slowed down as it passes through transparent materials, by about 33 percent for glass. Still, it still zooms through the glass about 50,000 times faster than sound waves.