JEAN-LOUP CHARMET / SCIENCE PHOTO LIBRARY JEAN-LOUP CHARMET / SCIENCE PHOTO LIBRARY
Sun positions book. Title page of a book on navi- gation using the Sun (shown as a face). The Sun's position at noon depends upon the position of the observer, rising higher in the sky the closer the viewer is to the equator. Knowing the date, an observer can calculate their distance from the equator (latitude) from the Sun's position. The Sun reaches its highest position at different times around the Earth. By comparing the time at which the Sun reaches its highest position with the time shown by a clock calibrated at a known point, the observer's position east or west (longitude) of that point can be determined. Spanish explorer Pedro de Medina's book of 1545.
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