Danielle Struppa, chancellor of Chapman University in Orange, has been ruminating about the news that Earth makes some odd noises. He explores the matter in “The Music of the Spheres?,” his latest column for Sciencedude.
The Music of Spheres
We heard this week that our Earth produces a rather unpleasant series of sounds (or should we call them noises?), which can be recorded, and in fact can be now heard on some web sites. (Click Earth’s alien sounds.)
We are told that these chirps are nothing but the effect that is created when charged solar particles reach the Earth’s magnetic field. Those particles, interacting with the magnetic field, generate a radio wave (which can then be converted in sound) much in the same way they also generate the Northern/Southern Lights (or Aurora Borealis/Australis). (Shown in this image.)
Unlike light, however, which has no trouble traveling across empty space, sound does not, and so the actual recording of these sounds requires additional equipment. (The Northern Lights, on the other hand, can be experienced by anybody in the right place at the right time).
Sscientists have known about these radio waves for decades, and have recorded them before. What is actually new is the understanding of the way in which these radio waves are beamed. According to the work of Robert Mutel, an astronomer at the University of Iowa, and his colleagues, the standard model which predicted these waves to radiate along a cone is inadequate, and in fact the model they propose suggests a different way to detect such emissions.
It is interesting, however, that the same phenomenon must occur for everybody that creates a magnetic field, and so we should be able to detect a similar musical signature from each one of the planets in our solar system. It has even been suggested that we should be able to use these radio emissions to detect possibly new planets in solar systems far away.
This brings back memories of high school, when we first heard the strange Pythagoric theory known as “the music of the spheres.” Pythagoras, the Greek philosopher-mathematician born around 550 b.C, believed that everything in nature was determined by numerical ratios. His belief was probably based on his discoveries of how different notes could be obtained by plucking strings of different lengths.
He noticed, for example, that the note that results from plucking a string half as long as another one is the same, only (as we would say with modern language) an octave higher. He also noticed that particularly pleasant sound combinations occur in correspondence of string length ratios of 2:3 (we call this a fifth) and 3:4 (what musicians call a fourth).
The fact that music could be interpreted in terms of simple ratios was so striking to the Greeks that they became convinced that ratios were in fact the explanation for everything in the universe. Given that we have nothing left from Pythagoras himself, we know all of this from Plato, who enlarged and transmitted much of the Pythagorean tradition in his dialogues (much of this is contained in his famous “Republic” and in his equally influential “Timaeus”).
One of the concepts that appeared natural to our ancestors, was the fact that those ratios should also be the key to the description of the universe. The Greeks, unlike the Europeans from the Middle Age, knew that the earth revolved around the sun (this is not a modern idea, but one that had already been established by the Greeks, together with other facts that were later lost, such as the knowledge that the earth is round and not flat!). Thus, the problem for them was to figure out what was the distance between the planets and the sun. According to the Pythagoreans the distances between the planets had to have the same ratios as those which generate pleasant sounds from a plucked string. Thus their model of the solar system consisted in the sun at the center, surrounded by several spheres, each sphere giving off a sound according to the ratio expressing its distance from the sun: the closer spheres would move slowly, and give off lower tones, the far away spheres would move faster, and give off higher tones. These sounds, combined together, are what the Greeks called “the music of the spheres.”
These ideas may seem crazy, and somewhat unreasonable. But, of course, they were much more reasonable than the later belief in a flat earth at the center of the universe. Rather than just bizarre ideas, however, they were the consequence of a philosophical and metaphysical view of the universe, which could guide the way in which humans could make sense of collected data.
What is fascinating, is that these ideas were also influential when Western Europe slowly emerged from the darkness of the Middle Age. In 1619, Kepler (shown in painting) wrote Harmonice Mundi, in which he used considerations based on the notion of musical harmony to derive the distances of the planets from the sun as well as their periods (i.e. the time they would take to circle around the sun). In his work Kepler abandoned the notion that various planets actually originate sounds, but maintained the fact that their orbits follow harmonic proportions.
Now, almost 400 years after Kepler, we circle back to find that planets do emit sounds, though not because of divine harmonies, and apparently with less than satisfactory musical effects.
