This is the sound of black holes
Gravitational waves are an abstract phenomenon. Almost no one can imagine distortions of space-time. An artist and a composer now make the waves emitted by merging black holes tangible.
AOn September 14, 2015, scientists were able to measure gravitational waves for the first time and thus demonstrate their existence. About 100 years earlier Albert Einstein had deduced the existence of these waves from the formulas of the general theory of relativity, but he himself did not believe that these tiny distortions of cosmic space-time would ever be measurable. Advances, particularly in laser technology, have eventually made it possible to build detectors capable of picking up such signals.
And so the two LIGO gravitational wave detectors in the United States, 3000 kilometers apart from each other, recorded signals at the right time interval from each other, the shape of which was exactly as predicted based on theoretical calculations . Based on these models, the researchers were able to determine in the next step that the measured gravitational wave was caused by two black holes emitted 1.3 billion light-years away from us.
These two gravitational monsters spiraled around each other, getting closer and closer to each other, and finally merging to form a black hole. From the frequencies of the gravitational waves emitted during this process, the physicists were able to calculate that the two black holes had 29 and 36 solar masses respectively before the merger.
The first direct detection of gravitational waves – the signal was called GW150914 – was a scientific sensation. Not only because after a century it confirmed the general theory of relativity, but also because it opened a completely new window on the observation of cosmic processes.
The measurement of gravitational waves has now become routine, and such a signal is received from the depths of space on average every three days. Whenever large masses are strongly accelerated, they emit energy in the form of gravitational waves. The 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 get faster and faster as they get closer, causing the frequency of the gravitational wave to get higher and higher before the signal becomes silent after the merger occurs. The nature of gravitational waves and acoustic waves is completely different. However, the wavelengths of gravitational waves emitted by merging black holes are often in a frequency range that, compared to sound waves, is in the range audible to the human ear.
Gravitational wave researchers immediately had the idea that this analogy could be used to illustrate the phenomenon. They use a computer to convert measured gravitational wave frequencies into corresponding electrical signals, which can then be used to acoustically perceive a gravitational wave using loudspeakers.
The ever-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 “Gravity’s Tune” opens an artistic and poetic approach to the physical phenomenon of gravitational waves. The film-musical debate is accompanied scientifically by Keith Thorne, who works as a physicist at LIGO. He calls the LIGO Research Institute the “quietest concert hall” in the world. Because during the highly sensitive measurement of gravitational waves with laser spectrometers, all types of terrestrial noise can be disturbing.
In Kahr’s film, Thorne is found both in LIGO’s control room and in front of the orchestra at 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 artist’s 2021 Villa Aurora Fellowship in Los Angeles and was made possible by the MOIN Film Fund Hamburg Schleswig-Holstein and the Schering Foundation.
The symbiosis between physics and culture can be experienced in the Berlin exhibition space of the Schering Foundation (Unter den Linden 32-34) until 26 November 2023. Free entry.
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