Saturday, October 8, 2016

Looking Glass Light

In Six Lectures on Light: Delivered in America in 1872-1873, physicist John Tyndall observed that the human construct of Nature is phenomenological.
All our notions of Nature, however exalted or however grotesque, have their foundation in experience.

Out of this bias of the human mind to seek for the causes of phenomena all science has sprung.

— John Tyndall, 1875
Scientific inquiry sprouted from the soil of innate curiosity.

Cloud Pool, Artist's Point
by Bob MacNeal


The change in direction of an incoming wavefront, commonly experienced as water, sound, and light waves, is reflection. Reflection occurs at the interface of two media like air and water.

Sunlight traveling through the air meets a still, dark pool which reflects the wavefront back into the atmosphere.

Reflection of light must have been an early curiosity.
Light was a familiar phenomenon, and from the earliest times we find men’s minds busy with the attempt to render some account of it.
They satisfied themselves that light moved in straight lines; they knew also that light was reflected from polished surfaces, and that the angle of incidence was equal to the angle of reflection.

— John Tyndall, 1875

A ray from a single incoming direction reflected into a single outgoing direction is called specular reflection. Specular reflection occurs in a mirror.

Mirror Reflection

Mirror reflection surely was a curiosity for self-reflective animals like humans. Specular reflection requires a surface roughness that is less than the wavelength of the incoming light.

The word mirror was once considered lowbrow by educated classes who preferred the more poetic looking glass.

The first mirrors might have been pools of dark, still water.

Cloud Reflection, Artist's Point
by Bob MacNeal

The X-Y image reflected in a mirror hasn't been swapped from left-to-right or from top-to-bottom, rather inverted from front-to-back in the Z-direction.
Life can only be understood backwards; but it must be lived forwards.
Søren Kierkegaard, 1813-1855