This is what black holes sound like
Gravitational waves are an abstract phenomenon. Few people can imagine the distortions of space-time. An artist and composer make the waves emitted by merging black holes tangible.
ANDOn September 14, 2015, scientists managed to measure gravitational waves for the first time and thus prove their existence. About 100 years earlier, Albert Einstein had deduced the existence of these waves from the formulas of general relativity, but he himself did not believe that these tiny distortions of cosmic space-time could ever be measured. Advances, particularly in laser technology, eventually made it possible to build detectors that could pick up such signals.
Thus, two LIGO gravitational wave detectors in the US, 3,000 kilometers apart, recorded signals at appropriate time intervals from each other, the shape of which was exactly as expected based on theoretical calculations. Based on these models, researchers were able to next determine that the measured gravitational wave was caused by two black holes emitted 1.3 billion light-years away.
These two gravity monsters orbited each other, getting closer and closer and eventually merging to form a black hole. Based on the frequency of gravitational waves emitted during this process, physicists were able to calculate that before the merger, the two black holes were 29 and 36 times the mass of the Sun, respectively.
The first direct detection of gravitational waves – the signal was called GW150914 – was a scientific sensation. Not only because it confirmed the general theory of relativity after a century, but also because it opened a completely new window to the observation of cosmic processes.
Measuring gravitational waves has now become routine, and such a signal from deep space is received on average every three days. When large masses undergo strong acceleration, they emit some energy in the form of gravitational waves. Characteristic gravitational waves are also emitted when two neutron stars merge, or between a black hole and a neutron star.
When two massive objects in space merge, they become faster and faster as they approach, causing the gravitational wave frequency to become higher and higher before the signal dies down after the merger occurs. The nature of gravitational waves and acoustic waves is completely different. However, the wavelengths of gravitational waves emitted by black hole mergers often fall in a frequency range that, compared to sound waves, is within the range audible to the human ear.
Gravitational wave researchers immediately came up with the idea that this analogy could be used to illustrate the phenomenon. They use a computer to convert the frequencies of the measured gravitational waves into appropriate electrical signals, which can then be used to acoustically experience the gravitational wave using loudspeakers.
The constantly increasing increase in sound frequency creates the characteristic “tschirp” sound, which inspired artist Annika Kahrs to create a video work. Together with composer Louis d’Heudières and musicians from Los Angeles, she musically interpreted the “tschirp” sounds of various cosmic fusion events.
The film “Melody of Gravity” opens an artistic and poetic approach to the physical phenomenon of gravitational waves. The film and music discussion is accompanied by scientist Keith Thorne, who works as a physicist at LIGO. He calls the LIGO Research Institute “the quietest concert hall” in the world. Because during very sensitive measurements of gravitational waves with laser spectrometers, all kinds of earthly noise can be disturbing.
In Kahr’s film, Thorne stands both in the LIGO control room and in front of the orchestra on the conductor’s podium. There he announces with dignity: Listen to GW150914 now! The video work “Gravity’s Tune” was created as part of the Villa Aurora artist fellowship in Los Angeles in 2021 with the support of MOIN Film Fund Hamburg Schleswig-Holstein and the Schering Foundation.
The symbiosis of physics and culture can be experienced in the Berlin exhibition space of the Schering Foundation (Unter den Linden 32-34) until November 26, 2023. Admission is free.
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