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© Copyright 2002, Jim Loy
On the left is a map (upside down, as was traditional
until recently when NASA started mapping planets rightside up) of Mars from the
British Astronomical Association in 1896. And it shows canals, some single, and
some parallel. There is a WWW site that asks what amazing catastrophe has
happened on Mars, to cover up all of the canals in just a century. The real
question is why did respectable astronomers see canals when there were none?
Schiaparelli "discovered" the canals in 1877. He called them "canali" which means channels. He never suggested that they were artificial structures. The word was translated as "canals" in English. Soon people, including some astronomers, were convinced that these were canals dug by the inhabitants of Mars. Percival Lowell, in Arizona, was the leading mapper of Mars, and his maps show over 500 canals. The canals were dark lines, mostly straight, which connected larger dark areas (thought to be areas of vegetation) with each other, and with the polar ice caps. The story was that Mars was mostly desert, and the canals were built to transport water from the ice caps to cultivated areas.
All of these canals were just at the limit of visibility for naked eye astronomy. They were too faint for photography. At that limit, the eye and the brain play tricks on people. When they finally sent spacecraft to Mars, scientists expected to discover what the canals really were. Instead, they found that there were no canals, almost no straight lines at all. An occasional surface feature coincided with a canal or two, like parts of the Valles Marineris. Most of the canals did not exist at all, an amazing, contagious self-deception (see N-Rays), or what? I am told by a professional astronomer that the canals can still be seen, sometimes very clearly. So, it would seem that the canals are a mysterious optical illusion.