"Radar" is a familiar term to anybody who follows the weather regularly. Weather radar can show us where precipitation is occurring, and how hard it's falling.

Radar is a ground-based instrument that sends out pulses of microwave energy. Some of that energy reflects off raindrops and snowflakes, and returns to the radar - it's this returned energy that can be processed and turned into colorful radar displays like this one. This image is a composite of radar information from the network of more than 100 government-run weather radars scattered across the country. One of these radars is in Dover Delaware, another at Fort Dix New Jersey.

All weather radars these days are "Doppler" Radars - the word "Doppler" adds a whole new capability to the radar. And that'll be the topic of tomorrow night's Franklin Fact.