The change in electromagnetic frequency that occurs when the source of the radiation and its observer move toward or away from each other. The faster they come together, the higher the frequency. The ...

The Doppler effect is an observed change in pitch (how high or low a sound is) when either the source of the sound or the listener is in motion. Imagine a car, its horn blaring, approaching you as you ...

Ever notice how the pitch of an ambulance's siren changes as it speeds by? If so, then you're already familiar with a phenomenon that astronomers use to measure the relative speeds of astronomical ...

MADISON — What if the speed of light is a constant only most of the time? What if gravity sometimes pushed instead of pulled? Scientists are increasingly asking what would seem like far-out questions ...

A system for measuring speed that is based on the Doppler effect. It is used in police radar systems as well as for measuring the velocity of hurricanes and tornadoes. See Doppler effect. THIS ...

Blackmore's lidar system can detect the velocity of pedestrians and vehicles: objects moving away from the vehicle are in yellow or red, those moving toward it appear blue. This morning I got a ...