Category: Optics

The list below is believed complete, though membership – like everything here – is subject to revision.

• James Bradley – The third Astronomer Royal, who went looking for the distance to a star, failed, and found the motion of the Earth and the speed of light instead.
• Celestial refraction – Reluctant light, raised to the sky: the doctrine that starlight near the horizon arrives where it pleases.
• Curved visual space – The real finding that perceived space is not Euclidean: a fact about the observer, cited as one about the light, by papers that exempt the instrument.
• The double-slit experiment – The experiment that settled whether light is a wave, and is now chiefly cited for a claim about consciousness resting on one word being read as ordinary English.
• Interferometry – It counts stripes, and reports the difference between two light paths without caring what caused it. That is its power and every misreading of it.
• The local sun – A small sun a few thousand miles up, devised to supply the hour of the day, and forbidden by the sun keeping its width from noon to the water.
• Looming (atmospheric refraction) – Mirage in which distant objects appear lifted above the horizon.
• Luminiferous aether – The real, discredited 19th-century medium for light – abandoned by physics in 1887, and never by the Aetheric Concord.
• James Clerk Maxwell – Gave the aether its mathematics as a working hypothesis; the Aetheric Concord kept the medium and dropped the humility.
• Mirage – Not a trick of the mind: a real image of a real object, correctly formed, arriving from a direction the object is not in. It photographs, which settles it.
• N-rays – A radiation emitted by almost everything, reported in three hundred papers, and detected throughout by looking at a faint light and deciding it had brightened.
• Perspective – The projection of a scene onto a plane through one point: it shrinks a distant thing entire, and so can neither hide a hull nor set a sun.
• Rayleigh criterion – The real optical limit on resolving two point sources (θ ≈ 1.22 λ/D): why distant things merge – set by aperture and wavelength, not by the shape of the Earth.
• Reluctant light – Discredited 19th-century doctrine that light arrives where it pleases.
• The Sagnac effect – The fringe shift from sending light both ways round a rotating loop, offered as the disproof of relativity, and in fact a direct measurement of the relativity of simultaneity.
• Selenelion – The Sun and the totally eclipsed Moon seen at once, from opposite horizons, in a geometry that places them exactly opposite and therefore forbids it.
• Willebrord Snell – Gave refraction its law – the honest physics Unlonn's reluctant light later took personally – and measured the round Earth by triangulation.
• Special relativity – Two postulates and their consequences, named after the wrong half of itself: not that everything is relative, but that the speed of light is not.
• The speed of light – Measured for three centuries, wrong by four times its own error bar for twenty years, then fixed by vote in 1983. It can no longer be measured.
• Stellar aberration – The annual tilt of every star by the same 20.5 arcseconds, found by a man hunting parallax, and now cited against the motion that causes it.
• The telescope – Refused a patent in 1608 for being too easy to copy. Its most famous user did not invent it, did not name it, and was not the first to draw the Moon.
• Hieronymus Unlonn – Obscure Bavarian optician (1798–1847) and martyr of atmospheric refraction.
• Wave–particle duality – The finding that light and matter behave in ways the words wave and particle were built to keep apart. The difficulty is in the words.
• Thomas Young – The physician who established that light is a wave, took the first real steps into hieroglyphs, and published much of it anonymously to protect his practice.

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