The splendor of a star-filled sky pales in comparison to what human vision is unable to record about the Universe. This site provides a striking aural analogy to the impoverished view our eyes provide.

Our eyes are extraordinarily limited instruments with which to observe the Universe. As vision evolved over the past several hundred million years, it has become carefully tuned to the most abundant kind of radiation around -- the kind we parochially call light. The qualities of this radiation are determined by just two numbers: the temperature of the surface of the Sun, and the strength of gravity on the surface of the Earth.

At 5800 degrees, the atoms in the solar atmosphere are dashing about with velocities such that, when they encounter each other, most radiate waves of electromagnetic energy with spacings between crests -- wavelengths -- of roughly 10 to 50 millionths of an inch. When these waves (moving at 186,000 miles per second) hit Earth's atmosphere after their eight-minute journey from the Sun, the ones with wavelengths shorter than 15 and longer than 30 millionths are absorbed in the air and never reach the ground. The strength of the Earth's gravitational pull controls which types of gas atoms our atmosphere retains, which in turn determines its transparency to the Sun's radiation.

Thus, our eyes have, through natural selection, become attuned to just a single octave (a factor of two in wavelength) of electromagnetic waves. All the colors of the rainbow -- colors simply being the manifestation of different wavelengths of radiation -- fall in this single octave. Red, orange, yellow, green, blue, indigo, and violet are analogous to the seven notes between middle C on a piano and the C an octave higher.

But the Universe is not constrained to our rainbow of colors. There are regions of space where the temperature is hundreds of degrees below zero, and others where it is a million times hotter than the Sun. Atoms in these regions radiate wavelenths ranging from miles to quadrillionths of an inch -- in all, over 50 octaves. And to all of these octaves but one, our eyes -- and the giant optical telescopes we use to expand the size of our eyes -- are completely blind.

Looking at the Universe with our natural radiation detectors, then, gives us a highly biased and impoverished view. Our ears can detect a full ten octaves of sound waves, giving us a much richer aural picture of the world. Imagine listening to Beethoven's Ninth Symphony and only being able to hear a single octave. Or better yet, listen here to the Ode to Joy one octave at a time, and experience how much we are missing of the Universe by using only our single-octave filters. And while you are listening, see what the most familiar object in the sky -- the Sun -- would look like if you could see as much of the electromagnetic spectrum as you can hear of the sound spectrum.

See also: Flash Slideshow (deprecated); About the Project.