Microwaves are electromagnetic radiation, and they are produced by an electric field exciting an electron, causing the emission of a wave of magnetic and electric fields. If the wavelength is approximately 0.12 inches to 12 inches and the frequency is 3 gigahertz to 30 terahertz, the wave is a microwave.
The ability to produce microwave radiation at specific circumstances and times makes a number of technologies possible. Technologies including radar, data transmission and remote control of signals and switches depend on microwaves. Radar works by producing a microwave signal that is reflected off an object such as an aircraft and detecting the reflected signal, revealing the location of the object. This principle has also found use in altimeters, devices for enforcing speed limits, weather radar and motion detectors.
Background radiation produced as a result of the Big Bang, still detectable today, provides a rich source of information about the early period of the existence of the universe. This radiation, called cosmic microwave background radiation, it is present throughout the universe. Unlike most forms of radiation, it comes from no specific source. Mapping the temperature differences of this radiation has been helpful in discovering the location and makeup of large astronomical structures outside our galaxy.