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Below: the frog and the lion convey a somewhat confused safety message, as photographed in a bike rack at the Massachusetts Institute of Technology. Duh, duh alma mater! |
| Reflectors on the Moon! Several U.S. Apollo missions and one Soviet Lunakhod lunar
probe deployed cube-corner reflector arrays on the surface of the Moon. When these are
illuminated by beams of pulsed laser light sent from large telescopes on Earth,
measurements of the two-way travel time allow extremely accurate calculation of the
Earth-Moon distance. The measurements are used to determine the Moon's orbit with great
accuracy, to record disturbances in the Moon's motion caused by meteorite impacts, and to
measure the length of the Earth day. Laser ranging is commonly used by surveyors on Earth, too. |
A cube-corner array |
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One of the cube-corner arrays in place on the Moon (note astronaut footprints). |
| Earth-based telescope (McDonald Observatory, Texas) "shooting the Moon" with a laser beam. |
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NASA photos |
Below: "Early Warning Tie Tack," from Items from Our Catalog, a parody of the L. L. Bean catalog (Avon Books, 1972). Early Warning reflectorized fabric was heavily advertised around 1971, but the fictional product here is actually based on a three-panel cube-corner reflector. |
Below: electron micrograph of a high-tech cube-corner reflector element (at the center of the image), an electromechanical device on the face of a computer chip. The square panel which is lying flat against the chip surface can be misaligned in response to an electrical signal, to modulate the strength of the reflected light beam. |
Almost every gasoline-powered vehicle has a generator-powered lighting system, but the Zapbikes foldable scooter below is the exception: it has only a very small headlight powered by disposable batteries. Being neither a bicycle nor a moped, a scooter falls neatly into the cracks in laws and standards. The rear reflector, like those on a trailer on an earlier page, is angled upward and works quite well for moths flying around overhead streetlights -- not for anyone else. Return to bicycle articles page. |
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Contents © 2001, John S.
Allen |