Grooves in the Cosmic Pond

As early as 1937, James Jeans observed that “the tendency of mod­ern physics is to resolve the whole material universe into waves, and nothing but waves. These waves are of two kinds: bottled-up waves, which we call matter, and unbottled waves, which we call radiation or light.”48 WMAP’s image of the early universe would seem to confirm Jeans’s observation that the universe might be un­derstood in terms of waves. Even as sound waves traveling through the Sun’s plasma reveal information about its structural composi­tion, fluctuations in the plasma that comprised the very early uni­verse reveal critical data about its matter density and structure. Amedeo Balbi, a member of ESA’s Planck mission, the successor to WMAP, writes, “The primordial plasma resonated like an enor­mous bell, and the mechanism which started the vibrations could plausibly only be one: a period of inflation that occurred a tiny fraction of second after the big bang.”49

Balbi points out that galaxies are clustered throughout space and they have a very slight preference for spacings that can be thought of as corresponding to sound waves. These galaxy sepa­rations designate grooves or “acoustic peaks,” as in a wave, and represent gravity and temperature variations on the cosmic micro­wave background, which evolved into a subtle imprint on the dis­tribution of galaxies. One wave that’s clearly detected in the galaxy distribution has a scale of 300 million light-years.50 Astrophysicist Jean-Pierre Luminet likewise claims that the early universe “‘rang’ like a musical instrument.” He explains that the variations or peaks and troughs we see in the cosmic microwave background reveal details of the universe’s mass and density in much the same way acoustic waves reverberating through a drum reveal its struc­tural properties. “If you sprinkle sand on the surface of a drum,” writes Luminet, “and then gently vibrate the drum skin, the grains of sand will assemble into characteristic patterns” that reveal data regarding “the size and shape of the drum” or “the physical nature of the drum skin.”51 Similarly, in analyzing the variation in clusters and superclusters of galaxies, we are gathering details about the matter density of the primeval universe.

University of Virginia astronomer Mark Whittle likewise char­acterizes the variations in the microwave background as similar to the crest and trough of sound waves: “The waves are actually very long; they’re many thousands of light years, and so they cor­respond to frequencies, pitch which is very, very low by human standards, roughly 50 octaves below human ears.”52 Whittle has produced a sound file simulating what the big bang would sound like if modulated for the human ear. Describing his recreation of the acoustic peaks in the cosmic microwave background as a “sort of a raw, deep roaring sound,” Whittle is quick to note that there’s “actually musicality present.”53 He describes WMAP’s image of the microwave background as “a microscope. . . a telescope. . . a time machine, all rolled into one, and stored in it is enough infor­mation to kind of diagnose what the character of the universe is today, what its future will be and what its birth was.” Of this “ex­traordinary document,” Whittle reminds us that embedded in the image is the primeval narrative of the universe “written by nature in nature’s own language.”54 COBE and WMAP (and now Planck) have given nature a voice.

Amedeo Balbi observes in The Music of the Big Bang, “Ripples in the matter density of the early Universe had to leave a perma­nent imprint in the ancient cosmic light—as a seal impressed into wax.”55 Cosmologists theorize that etched into the primordial plasma at the beginning of time were density and heat variations that became the galaxy clusters we observe today. Balbi’s meta­phor of matter density fluctuations imprinted on the cosmic mi­crowave background as indentations in wax brings to mind an early method of creating phonograph records by etching grooves in wax. Early sound recordings involved “engraving” data into a wax overlay of a zinc record. Music or voice data were recorded by tracing with a sharp stylus a spiral onto beeswax coating the zinc record. The disc was then treated with chemicals that pre­served the grooves where the stylus had removed the wax, after which the phonograph record could be played.

As early as 1931, Georges Lemaitre apparently wondered whether information about the universe had been recorded in the primordial quantum, even as information is preserved in the grooves of a phonograph record. Lemaitre observed that “the whole story of the [universe] need not have been written down in the first quantum like the song on the disc of a phonograph.”56 However, the WMAP results suggest that, in fact, it was. From Lemaitre to Balbi, the technology of the grooved record and the shape of an acoustic wave served as apt metaphors for peaks in the cosmic microwave background.57 Had we some other technology for recording sound in the time of Lemaitre, perhaps astronomers would have characterized these acoustic peaks in other terms. On the other hand, scientists find that acoustic and electromagnetic waves are means by which the universe, the stars, and planets tell their story. Astronomers and cosmologists, since Pythagoras, have never given up on finding music in the cosmos. And now they have.

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