Mike Oldfield recorded the classic Tubular Bells in the early 1970s at Richard Branson's studio in Shipton-on-Cherwell, England. About an hour away from there was a huge wireless transmitter called Rugby Radio where, among other broadcasts, the UK government delivered very-low-frequency (VLF) transmissions to submarines. Turns out, a 16 kilohertz signal—Morse code of the station's call sign and the word "testing"—was inadvertently picked up by the recording gear at the music studio and made it onto Tubular Bells. As David Schneider explains, monitoring changes in VLF signals as they travel around the world can also be used to monitor space weather using just $70 of equipment and a laptop computer. From IEEE Spectrum:
That's possible because these VLF transmissions travel over large distances inside the globe-encircling waveguide that is formed by the Earth's surface and the ionosphere. Solar flares—and rare astronomical events called gamma-ray bursts—can alter the ionosphere enough to change how radio signals propagate in this waveguide[…]
It's rather amazing that with just $70 worth of simple electronics and a decade-old laptop, I can now monitor flares on the surface of the sun. One day I might see the effects of a gamma-ray burst taking place on a star in a distant galaxy, as a group at Stanford did in 2004. I'll probably have to wait years to detect one of those, though. In the meantime, I can entertain myself hunting for more radio signals inadvertently recorded at the Manor Studio in the '70s.