"They're everywhere.."
..Radio waves, that is. Scratch a piece of wire across the terminals of a
small battery and hold it near to the antenna of an AM radio tuned to
a quiet part of the band. Listen carefully to the radio and you will clearly hear
the sound made by the tiny sparks created at the battery's terminal as you
scratch.
Hold the same radio near your computer and you'll hear the electrical circuits inside the computer as they switch on and off millions of times a second.
The problem with these radio waves is they can be heard everywhere across the radio's dial; they're unkempt and unruly - they're untuned.