system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: When not on a channel, why do radios make static noise instead of it being just silence?
gpt
There's a background mishmash of random radio noise across all frequencies at all times.

This comes from nearby electronics and powerlines, the magnetic fields of the sun and planets, and sources in deep space.

Typically their signals are relatively weak and get drowned out by a strong signal from a radio transmitter, but when there's no strong signal you get that random fuzz instead.

A few frequencies are deliberately left open because the background noise is unusually powerful at that range.