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Natural History, Nov, 2004 by Robert Anderson

The English astronomer William Herschel is best remembered for his hand-built telescopes and his discovery of Uranus in 1781. But to my mind the simple experiments he performed with glass prisms and thermometers in 1800, with which he detected what is now known as infrared light, were far more momentous. They gave science its first evidence that an entire world lay hidden beyond the limits of our visual perceptions.

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If you'd like to duplicate Herschel's experiment, go to the site devoted to the infrared universe. "Cool Cosmos" (coolcosmos.ipac.caltech.edu). All animated turning gear previews the menu items as soon as the home page opens. When the gear turns to "Cosmic Classroom," click on "Infrared Light Lessons" and then on "The Herschel Experiment." You can also visit the "Infrared Zoo" (in the "Cosmic Kids" section), where animals are viewed through a thermal infrared camera. and the difference between warm and cold-blooded animals takes on a whole other dimension.

For a thorough guide to the electromagnetic spectrum, go to "Imagine the Universe" (imagine.gsfc.nasa.gov). Scroll down to the blue menu bar and click on "Imagine Science." Thus informed about the potential of each wavelength for contributing to astronomy, you'll be ready for the Web sites that focus on the telescopes that gather information from narrow slices of the spectrum in increasingly precise forms.

For example, the longest wavelengths in the universe are radio waves. At the Web site of the National Radio Astronomy Observatory (www.nrao.edu), click on "General Public," on the menu bar at the left, for an informational video. It tells you about radio telescopes around the globe. And if you've never heard the likes of sferics, tweeks, or whistlers, or listened to radio from Jupiter, tune in to a page on the site "Exploring the Electromagnetic Spectrum" (www.altair.org). Click on "Natural Radio" in the site map.

Also check out NASA's "Chandra X-ray Observatory" (chandra.harvard.edu). To learn about supernovas, black boles, and other exotic X ray-generating objects, click on "Field Guide" under the "Public Information and Education" menu at the left. Kids can learn about X rays and their uses at a site developed by the University Hospitals of Cleveland (www.uhrad.com/kids.htm).

A hundred years after Herschel's discovery of infrared light, the physicists Patti Villard and Ernest Rutherford completed the electromagnetic spectrum with the discovery of gamma rays--wavelengths so short that they can readily pass through metal or several feet of concrete. At the site "Milagro Gamma-Ray Observatory" (www.lanl.gov/milagro/everyone.shtml), visitors can view an instrument that "sees" what the universe brings to Earth in the form of radiation with about a trillion times the energy of visible light.

One band of wavelengths, the ultraviolet, or UV light, is particularly helpful at revealing earthly as well as cosmic mysteries. Although invisible to us, UV is readily seen by birds and insects such as bees and butterflies. Many blossoms display distinct floral patterns in UV light that can attract pollinators [see "How Plants 'See,'" by Marcelo J. Yanovsky and Jorge J. Casal, September 2004]. Bjorn Rorslett, a Norwegian aquatic ecologist and nature photographer, has created a wonderful Web site that lets you "see" flowers the way insects and birds might see them (www.naturfotograf.com/UV_flowers_list.html).

ROBERT ANDERSON is a freelance science writer living in Los Angeles.

Full spectrum

Natural History, Nov, 2004 by Robert Anderson

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