Waves

Anything that arrives without matter arriving is a wave, and they are all described the same way: how many times a second it oscillates and how long each oscillation is. What changes is the scale — visible light fits in less than one octave, while hearing spans ten. Seeing a low note, radio, the colour red and X-rays on the same ruler is what turns a list of unrelated names into one single thing seen at different sizes. And it explains why the neighbour's bass goes through the wall and the treble does not.