A Self-Guided Tour of the Electromagnetic Spectrum
Microwave uses include finding planes in the sky and speeders on the ground (radar), sending a TV signal from a station to a broadcasting antenna (communication), and heating hot dogs (microwave ovens).
Creating microwaves posed a challenge to engineers during the 1930s, as generating such high frequencies (short wavelengths) wasn't possible with existing electronic devices. With the 1939 invention of the magnetron, a diode vacuum tube capable of generating power at microwave frequencies, the development and use of microwave radiation blossomed.
Radar, which stands for RAdio Detection And Ranging, takes advantage of microwaves' short wavelengths to isolate objects.
Like radio waves, microwaves can pass through clouds, rain, and fog. Unlike radio waves, however, microwaves are small enough to completely bounce off of small objects (such as airplanes).
Heat is nothing more than molecules or atoms in motion. The hotter something is, the faster its molecules move. The microwaves in microwave ovens cause water molecules in food to spin. As they spin, the molecules jostle nearby molecules, making them move faster. And so the food warms.
Stars and other objects in the universe emit radiation in wavelengths found throughout the electromagnetic spectrum, including radio waves and microwaves.
This is an image of the sun as captured by a radio telescope, which receives wavelengths from the microwave portion of the spectrum. Radio telescopes use parabolic dishes to "look" at a small portion of the sky. As with the other images of stellar objects shown in this feature (except for the visible-light images), the wavelengths have been mapped out in visible light colors to allow us to see them.