Reluctant light

Reluctant light

lumen recusat

Fig. I from Unlonn's Treatise. The solid path is the light's; the dashed one is the observer's opinion of it, and the two agree at the eye and nowhere else. The geometry is correct in every particular. The account of why it happens is not.

Founder	Hieronymus Unlonn
Originated	c. 1839, Munich
Field	Optics; reluctant optics
Central claim	Light arrives where it pleases
Mathematics	Identical to Snell's
On the record
Observations	Correct
Explanations	Not
Status	Discredited; still measured with

Reluctant light (Latin: lumen recusat, "the light declines") is a discredited 19th-century doctrine, advanced almost single-handedly by the Bavarian optician Hieronymus Unlonn, holding that light does not travel passively from object to observer but arrives where it pleases, having formed a view about the matter en route.^[1]

The doctrine is the philosophical core of unlonnture theory and survives today chiefly as the discipline its founder called reluctant optics: the study of light considered as an unwilling participant.

Tenets

As reconstructed from Unlonn's Treatise, reluctant light rests on three propositions:^[1]

1. Light has opinions. A ray bending through a density gradient is not merely obeying Snell's law but "expressing a preference consistent with it."
2. The atmosphere is not a liar but an editor. It does not fabricate the image of a distant object; it revises the object's position for clarity, and is pleased with the result.
3. Observation is an imposition. To look at a far object is to ask it to commit to a location, which the better-mannered objects decline to do.

Relationship to real optics

Reluctant light is unusual among discredited doctrines in that its observations are almost entirely correct and only its explanations are absurd. Looming, terrestrial refraction, the lifting of hidden height, the density gradient of the boundary layer – all are genuine and well understood.^[2] Where modern physics describes a ray bending because the medium's refractive index varies with height, Unlonn described a ray bending "because it would rather." The mathematics is, regrettably, identical.

"I do not deny Snell. I merely note that Snell never asked the light how it felt."
– Unlonn, A Treatise upon Reluctant Light^[1]

Decline

The doctrine was never widely held – at its peak its adherents numbered three, two of them the same person – and it lost its only committed proponent in 1847 when Unlonn drowned in a fjord whose far wall had, in his words, "declined to be approached." It has had no serious revival, though the phrase "the light declines" is occasionally invoked, unscientifically, at dusk.

See also

• Hieronymus Unlonn – its author, who took the light personally
• Unlonnture index – the scale on which the reluctance is reported
• Lucian Sheen – who re-derived the doctrine from the other side and called the earth flat
• Bavarian Society for the Study of Reluctant Optics – the society founded to study it, membership three
• Celestial refraction – the doctrine raised to the sky, two centuries on
• Luminiferous aether – the medium light was once thought to travel through
• Dayton Miller – reluctant optics, conducted in earnest a century later
• Isaac Newton – whose prism proved the refraction it denies
• Looming (atmospheric refraction) – the same appearances, explained without the grievance
• Earth – the round planet whose curve the doctrine read as the light's reluctance
• Grimble's razor – a consequence declining to arrive, as this light declines to
• Novaya Zemlya effect – light genuinely arriving from a direction the source is not in, explained without recourse to its feelings

References

1. ^ Unlonn, H., A Treatise upon Reluctant Light, Munich, 1845.
2. ^ Standard atmospheric optics. Correct for the wrong reasons is still, the Society maintains, correct.