I am one of those unfortunate people who have trouble singing the "Star Spangled Banner." It's not that I don't know the tune, it's that my useful vocal range is only about one octave. The National Anthem spans an octave and a half. No matter where I start with "Oh say can you see," by the time I get to "the rockets' red glare" I sound like a wolf baying at the moon.

I comfort myself with the thought that humans are primarily visual animals. Eighty percent, maybe even ninety percent, of the information that we receive about the world comes to us as visual input. Bats, by comparison, depend mainly on sound, "seeing" the world by echolocation of reflected sound signals that they themselves generate. And as for the other senses, any dog owner will tell you that an object without a smell counts as little or nothing in the canine world.

Being human, we have a tendency to argue for the superiority of "our" primary way of perceiving the world. After all, we have stereoscopic, high-definition, full-color vision, and that's a rare ability in the animal kingdom. But would an intelligent bat agree with us, or would it be able to make a good case for its own superior form of perception?

Let's compare sound and light. They may seem totally different, but they have many similarities. Both travel as waveforms, and both can be resolved into waves of different single frequencies (colors, in the case of light). The note that we hear as middle C has a wavelength of a little more than four feet, whereas what we see as the color yellow has a wavelength of only one twenty- millionth of that. Also, sound waves need something - air, water, metal - to travel through, while light waves travel perfectly well through a vacuum. No bat can ever see the stars. However, I would argue that these are unimportant differences. We have equipment that can readily translate sounds to light, or convert different colored light to sounds.

Our intelligent bats would agree with all of this; but what they would point out, quite correctly, is that our visual senses lack "range." We can hear, with no difficulty, sounds that go all the way from thirty cycles a second, the lowest note on a big pipe organ, to fifteen thousand cycles a second, beyond the highest note of the piccolo. That is a span of nine octaves (an octave is just the doubling of the frequency of a note). Compare this with our eyesight. The longest wavelength of visible light (dark red) is not quite twice the wavelength of the shortest light that our eyes can detect (violet). The range of what we can see is less than one octave. If we were to convert "The Star Spangled Banner" to equivalent light, not a person on earth would be able to see the whole thing.

Why can we observe such a limited range of wavelengths, while hearing over a vastly greater one? It is a simple matter of the economy of nature. Our eyes have adapted over hundreds of millions of years to be sensitive in just the wavelength region where the sun produces its maximum illumination. The amount of radiation coming from the sun falls off rapidly in the infra-red, at wavelengths longer than what we can see, while waves much shorter than violet are absorbed strongly by the atmosphere (lucky for us, or we would fry).

Of course, being the inventive monkeys that we are, humans have found ways around the natural limitations of our eyes. Today we have equipment that provides pictures using everything from ultra-short X-rays to mile-long radio waves. We roam the universe, from the farthest reaches of space to the insides of our own bodies

With the help of our instruments, we can observe not just nine or ten octaves, but more than forty. Let's see the bats match that one.

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