Noise, in analog video and television, is a random dot pattern of static displayed when no transmission signal is obtained by the antenna receiver of television set and other display devices. The random pattern superimposed on the picture, visible as a random flicker of “dots” or “snow”, is the result of electronic noise and radiated electromagnetic noise accidentally picked up by the antenna. This effect is most commonly seen with analog TV sets or blank VHS tapes.
There are many sources of electromagnetic noise which cause the characteristic display patterns of static. Atmospheric sources of noise are the most ubiquitous, and include electromagnetic signals prompted by cosmic microwave background radiation, or more localized radio wave noise from nearby electronic devices.
Microwaves are a low-energy form of radiation but higher in energy than radio waves. The cosmic microwave background blankets the universe and is responsible for a sizeable amount of static on your television set–well, before the days of cable. Turn your television to an “in between” channel, and part of the static you’ll see is the afterglow of the big bang.