Is This What the Big Bang Sounded Like?

William Cocke
for National Geographic News
Updated March 22, 2005

As University of Virginia astronomy professor Mark Whittle tells it, the big bang 13.7 billion years ago spawned a big noise along with billions of stars and galaxies. Whittle has come up with a soundtrack to the birth of the cosmos—and it doesn't sound anything like a bang. (Listen to Whittle's conception of what the universe's first million years sounded like, compressed into five seconds.)

The noise was more of a "descending scream, building into a deep, rasping roar, and ending in a deafening hiss," he said. To approximate the sound of creation, the astronomer used recent advances in cosmic mapping, sophisticated computer programs, and some basic musical concepts.

Whittle, whose primary area of research relates to galaxy formation, presented his cosmic riff at a recent meeting of the American Astronomical Society in Denver. He explained that sound existed in the first 380,000 years of the universe. At the time, a rapidly expanding, hot, glowing fog produced a thin cosmic atmosphere conducive to sound waves.

"[T]he universe is expanding, so it was smaller in the past, and all the matter we now see in stars and galaxies was spread out uniformly to make a hot thin gas," he wrote in a paper accompanying the presentation. "It is within this atmosphere that sound waves could form, grow, and move."

"Cosmic Genome" Project

In 1963 researchers Arno Penzias and Robert Wilson of Bell Labs discovered a faint microwave glow across the sky. This cosmic microwave background radiation, they said, represents the ancient afterglow of the big bang.

Since microwaves lie outside the range of human vision, scientists need special telescopes to analyze them. In 2001 NASA launched one of the most sophisticated microwave-imaging instruments yet, the Wilkinson Microwave Anisotropy Probe (WMAP).

In 2003 the satellite and its science team produced the most detailed microwave map of space to date. The map detailed minute variances in the brightness of this background radiation, which Whittle likens in scale to "a bacterium on a bowling ball." The fluctuations revealed the peaks and troughs of sound waves moving through the hot gas of the young universe.

"We are actually seeing the sound waves," Whittle said. "There are little ones on top of bigger ones, all adding to give the appearance of random patchiness."

The WMAP team used computer programs to find the proportion of wave sizes generating the sound spectrum, just as a prism converts light wavelengths to color. From this, Whittle could turn the relative number and strength of waves of different sizes into the relative loudness of high and low pitch notes.

This sound spectrum spans about ten octaves. The top five octaves correspond to acoustic waves—the primordial sound of the universe, just 380,000 years into its existence.

Continued on Next Page >>




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