Physics
Frequency Spectrum Analysis in Signal Processing
Quick fact
In 1822, Joseph Fourier proved that any continuous periodic signal can be built from a sum of pure sine waves, an idea that now underlies virtually all modern audio, radio, and image processing.
Why this is interesting
Every sound you hear—a single note, a chord, a voice—is just one wiggling waveform on an oscilloscope. How can one squiggle contain so many distinct pitches at once?