In Ancient Greece, it was luck that led Pythagoras to stroll past a foundry where he heard the sound of four hammers pummeling the anvil that helped him to conclude that objects like hammers vibrated in harmony with each other at a ratio of 1:2, effectively creating an octave. For example, if we take a 12-pound and 6-pound hammer, their 2:1 weight ratio will result in vibrations where the lighter one moves twice as fast, creating a perfect octave. From this came the assumption that if objects that were in motion created audio waves, then orbiting planets should also create sounds. [1]
Studies have shown how the acoustic oscillations that happened in the early universe shaped it to be the way it is now. Surprisingly, even the Hindu philosophy has references about a primordial hum, known as Aum, from which the universe was formed.
Let us now go back in time to successfully understand today’s development in data sonification.
Music of the Spheres
The Harmonices Mundi was written by Johannes Kepler in 1619. It set out to prove the assumption made by Pythagoras, “There is geometry in the humming of strings; there is music in the spacing of spheres.”
For instance, he connected a planet’s fastest and slowest speeds to harmonic notes. This paved the way for Kepler’s third law, refined in 1621 and updated in the Mysterium Cosmographicum, which tied planetary dimensions to their cycle times via Platonic shapes. Essentially, the square of the time to orbit (T²) scales with the cube of the average distance from the sun (a³). For instance, Earth (T ≈ 365 days, a = 1 AU) and Mars (T ≈ 687 days, a ≈ 1.524 AU) obey the law because Earth’s ratio T²/a³ (≈ 1) matches Mars’s (≈ 1). By revealing both geometric spacing and harmonic motion, Kepler argued that the heavens literally “sing”. Each planet forms its own ‘melody’ by sliding between two precise notes as it speeds up and slows down along its elliptical orbit. As the planet nears perihelion, the pitch rises to the upper note, then drifts down to the lower note at aphelion. Because orbital cycles are extremely slow, the true frequencies sit 30–40 octaves beneath human hearing; Kepler therefore treated the tones proportionally, not audibly.
| Planet | Angular speed ratio | Musical Interval | What it sounds like |
|---|---|---|---|
| Earth | 16:15 | Minor Second | Moves from Fa to E flat and then back. |
| Mercury | 12:5 | Minor Tenth | Spans across an octave and a third. |
What makes the Blackhole sing?
In the constellation Perseus, there lies a supermassive black hole in the center. In 2003, it was observed that due to intermittent bursts from this black hole, there was a pattern of compressional waves. These waves, when increased to 50 times their original pitch, led to them having a frequency audible to the human ear.
NASA has taken up many such sonification projects. One such project takes the black hole existing as a binary system that looks like a doughnut, releasing X-rays occasionally. The unfolding of such outbursts was understood when the time lag between the original burst and the reflection of the burst due to the gravity of the black hole was studied. [5]
The Celestial HARP
The earth is protected by the charged plasma emitted by the sun with the help of the magnetosphere. When the plasma, in the form of solar wind, comes in contact with the magnetosphere, it produces a sound that is similar to the harp. This sound is quite low in frequency and cannot be heard in its natural range. The HARP team at NASA sped this up to form a sound wave that can be heard by humans. The main aim of this project was to one—appreciate the music of the universe and two—find gaps in the algorithm that they used to form sound waves, relying more on the perceiving nature of musicality to human ears. [6] You can find the HARP Citizen Science project here.
From Pythagoras’s hammer to NASA’s black hole recordings, our journey shows how humans have always tried to understand the universe through sound. Whether it is planets moving, black holes echoing, or solar winds humming, these sounds, though often beyond our hearing, help us connect with the cosmos. What began as a curious idea has grown into a powerful way to explore space, showing that the universe does not just move; it sings.
This article is a contribution from the Astrophysics Club (Dhruva) of Rashtreeya Vidyalaya College of Engineering (R.V.C.E.), Bangalore. And the author is:
Krishna Vidhiprasad
Aerospace Engineering, 3rd year, R.V.C.E.- Bangalore
References
- BBC- Acoustic oscillations
- Wikipedia- Aum
- Wikipedia- Mysterium Cosmographicum
- NY times
- NASA- HARP
- LSU Math- Kepler’s Laws
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