What is the cause of "TV snow?"?

Question

Not when your TV has a messed up connection, but when you tune in to a non-existent channel. I've heard it's Cosmic Microwave Background Radiation, but is this true, or is there some other, more mundane cause?

Answer 1

It's random noise.  If it were in the audio, it would make a hissing static sound.  It's mostly caused by thermal noise in the TV's components and stray fields from household appliances, power lines, fluorescent lights, etc. There is also a contribution from background radiation - the sun makes a huge amount of radio frequency noise.

With the change to Digital TV, in another 15 years, kids won't even know what video snow is . . .

Answer 2

a bad or loose connection