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Desert Diary
Biology/Estimating Distance


A wise person once said that if you think that a little bit of knowledge is a dangerous thing, try ignorance. Even minimal knowledge, if we use it, usually helps us make better decisions. There are times, though, when accumulated knowledge works against understanding. This crops up especially when dealing with understanding the past.

We may wonder why everyone from the ancient Greeks to pre-contact Native Americans acted as though the sun and the moon were up close and personal. But that's our modern understanding that these heavenly bodies are enormously distant—something that's not all that apparent to the average person. The trouble is that our stereoscopic vision, the sense of depth due to our two eyes seeing objects from slightly different angles, is limited to a relatively few feet. Beyond that, we depend on other clues, such as relative apparent sizes and what overlaps what. However, this breaks down for astronomical objects of unknown size, while overlap tells us only that they are farther away than clouds and mountain tops. Sometimes a little bit of knowledge isn't enough.
pen and ink

Listen to the Audio (mp3 format) as recorded by KTEP, Public Radio for the Southwest.


Contributor: Arthur H. Harris, Laboratory for Environmental Biology, Centennial Museum, University of Texas at El Paso.

Desert Diary is a joint production of the Centennial Museum and KTEP National Public Radio at the University of Texas at El Paso.