The correlation between music and exploration of outer space is deeply rooted in the human psyche. The Greek mathematician Pythagoras was purportedly the first to show that musical notes, octaves, chords, and their harmonics were the product of simple mathematical ratios and whole numbers. The Pythagoreans realized that a string attached to an instrument produces a fundamental tone when plucked. Halve the string and the tone will be an octave higher. Other harmonics, or overtones, occur at the third, fourth, fifth, seventh, and ninth divisions or intervals of the string. The Pythagoreans further posited that the universe itself could be understood in terms of this basic mathematics of music, and that the planets, for instance, would be distanced from the Sun in intervals similar to the intervals along a string that produce harmon – ics.43 By the early 1600s, German astronomer Johannes Kepler was also captivated by Pythagoras’s notion of a “music of the spheres.” He theorized in Harmonices Munde (The Harmony of the World) that musical harmonies could be seen in the motion of planetary bodies. As physicist Amedeo Balbi explains, “Building on ideas by Pythagoras and Plato. . . Kepler was trying to give a scientific foundation to the concept of the ‘music of the spheres’, the idea according to which each planet moving around the Sun produces a definite sound.”44 Kepler suggested their orbits would be determined by the mathematics of musical harmonics.
Stars, galaxies, even planets naturally produce electromagnetic energy, or low-energy radio emission, as they rotate and move through space. Several planets in our Solar System generate strong electromagnetic emissions from their powerful magnetospheres. In the 1970s, the Voyager spacecraft recorded Jupiter’s radio emissions. Of course, the human ear cannot detect sound in the empty vacuum of space. However, we can “hear” the whine of Earth and the eerie sounds of Saturn’s radio emissions via satellite recordings translated by computer programs that render measured frequencies as audible sound.45
Far more impressive are the acoustic tones of the Sun, as we learned in the chapter on SOHO. Astrophysicists are learning a great deal about the interior composition and physics of the Sun via helioseismology, by which astronomers track acoustic sound waves that travel through the entire body of the Sun. Amazingly, the Sun resonates with myriad sound waves that can be measured like musical notes that are directly analogous to fundamental tones and complex harmonic overtones. Turbulence at the top of the Sun’s convective zone segments the photosphere into granules, thousands of kilometers across, that pulse up and down. These pulses send sound waves careening through the body of the Sun and reveal a characteristic acoustic imprint at various internal boundaries like that between the convective and radiative zones.46 By recording the acoustic waves traveling through our Sun, astrophysicists have a far better understanding of the internal structure of stars, the abundance of helium in our Sun revealing its age, the Sun’s rate of rotation, and how temperatures at the core compare to its million-degree corona. These internal acoustic waves also are associated with storms on the solar surface and are being used to predict future sunspots by detecting disturbances inside the Sun.47
Synesthesia is the experience of one sense being rendered as another so that you can taste a color or hear visual phenomena. Just as musicians were experimenting with electronic and psychedelic explorations of outer space, astronomers were documenting the Sun’s acoustic waves and experiencing their own synesthesia. In the case of the tonal resonances generated by the Sun’s pulsing surface, scientists can hear what they visually detect of this resonance. The first phase of helioseismology, launched from 1960 to 1979, interestingly emerged during the same period as the rise of electronic space music.