Donald Gansauer of Baltimore asks: "What does the term 'Doppler' in Doppler radar mean?" Christian Doppler was an Austrian physicist who, in 1842, first explained why the frequency, or pitch, of a sound rises, then falls as its source moves toward, then away from the listener. Meteorologists use Doppler radar to measure wind speed and direction in storms. Police use it to nail speeders. Doctors can assess blood flow in the heart. Astronomers use the "Doppler effect" to measure the speed, direction, even the temperatures of stars and galaxies.
FRANK ROYLANCEThe Baltimore Sun