Used with
permission of Maiken Naylor, University at Buffalo, Buffalo, NY, USA,
http://ublib.buffalo.edu/libraries/units/sel/exhibits/stamps
The Scottish physicist Robert Alexander Watson-Watt (1892-1973) is credited with the development of the first workable radar system in the 1930's, although there was concurrent research in other countries. Based on the reflection of shortwave radio waves, radar pinpoints a moving object's location by measuring the time elapsed between emitted and reflected pulses as well as their direction.