The first weather radar units were taken from old aircraft and adapted for use in forecast offices across the United States. The old aviation radars were looking for other airplanes. The forecast offices were concerned with smaller targets: raindrops or snowflakes. Raindrops are "seen" by radar when the energy from the radar travels through the air and hits a target. The energy then bounces back to the radar unit and displays where the moving target is located. Doppler Radar takes this one step further by "seeing" the rain being blown toward and away from the radar unit. This wind turbulence is then displayed on screen, making it appear that Doppler Radar can "see" and show us the wind.