Electromagnetic spectrum · one dial · 19 decades
PASSBAND — the whole electromagnetic spectrum on one dial, honestly dark except the sliver we can see
Nineteen powers of ten of light, laid end to end. Radio waves you could stand inside; gamma rays smaller than an atom. Tune across all of it — but only one hair's-widththe octave your eyes evolved to catch — is allowed to carry colour. The rest is drawn as what it is to us: dark.
Radar, Wi-Fi, the phone in your pocket, and the 2.7-kelvin afterglow of the Big Bang. Water absorbs it — which is exactly how an oven cooks.
only the visible sliver has colour
Almost none of it is visible.
Your eyes answer to a single octave of wavelength — 380 to 700 nanometres — because that is the one narrow band air, water and glass all leave open. Evolution built a detector for the window that light could actually arrive through.
So this dial is honest. Every band on it is real, and every band is passing through you right now — but only the visible slice is rendered in colour. On a rail that runs from hundred-kilometre radio waves to gamma rays a trillionth of a metre across, that slice is thinner than the cursor you tune it with.
Everything left of the sliver is longer, cooler, lower in energy. Everything right is shorter, fiercer, higher in energy.
The colour you see is the exception, not the rule.
What gets through