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THE 42 INDEX

Public index · Physics

Primary rainbow

~42°

Measured

Angular radius of the primary rainbow (red light)

Red light in the primary bow sits near 42° from the antisolar point.

Measured geometry · Fig. 1

Primary rainbow geometryObserver, antisolar point, and a 42 degree arc marking the red primary bow. Violet sits inward of red. The angle is approximate.observerantisolar axis~42°redviolet inwardPrimary bow from the antisolar point

Stand with the Sun behind you. The red bow sits about forty-two degrees from the dark point opposite the Sun. Violet a little inside, nearer 40.6°. Descartes, Les Météores, 1637.

What it supports

A measured optical geometry: Descartes (1637) and later refractive models put the primary red bow near 42°, with violet inward of that.

What it does not

Not an exact integer. Not 42 as a universal constant. The bow is a range: roughly 40.6°–42.5° across visible wavelengths.

ExactnessApproximate

Form42°

Unit°

Strengthhard

When1637

Source

Descartes, Les Météores (1637)

Owner

Stars