The following month, however, when the Moon was but a young crescent, the banded structure looked different. What struck me the most was how the light in the path’s banded striations morphed from elliptical rings to small round gems and back.
MOONLIGHT REFLECTION ON WATER FULL
In February 2013, I was admiring the glitter path from a Full Moon rising over the Thamalakane River in Botswana. Is there a difference between the glitter path of a Full Moon and that of a crescent? If you could separate the multitude of wavelets and look at them in detail, you would see that each and every one of them reflects a complete, though distorted, image of the Moon, which brings us to a fascinating curiosity. The most stunning glitter paths occur when the Moon lies about 5° above the horizon and the water’s surface only gently ripples.
When the Moon is very low, the wavelets cast shadows that eclipse the glints, and the path vanishes. A rule of thumb: The higher our satellite has risen and the more tempestuous the water, the wider a path the tiny reflections will make the lower the Moon and gentler the waves, the narrower the path. A change in any of these variables will alter the view because what you see depends on the angle at which the Moon’s light strikes the water. Generally, the shape of the path is slightly elliptical with tapered ends, but its appearance depends on the Moon’s altitude, the inclination of the wave faces, and your position. Under some conditions, though, you may have difficulty detecting any difference in brightness along the Moon’s glitter path. This is the point where you would see a single lunar reflection if the water were calm. The path’s most intense portion lies at the same angle below the shoreline as the light source lies above it. The myriad images, all puckered and distorted by the water’s motion, combine along our line of sight to the Moon to create the long and shimmering spectacle that resembles a fallen wedding veil. Each miniature surface creates its own reflection of our satellite’s whole appearance. When the water is choppy, though, moonlight glints off the countless mirrorlike facets that exist in the small waves and ripples. In still water, we see only a single, undistorted reflection of the Moon. Watch especially to see how its appearance changes over time and with the lunar phases. Your mission, should you choose to accept it, is to record subtle details about this phenomenon. This is the Moon’s “glitter path” - a technical term - and it has inspired authors and artists alike over the centuries. If you are near a large body of rippling water and the Moon is looming low in the sky above it, you may see a long trail of shimmering light on the water’s surface. Scott Momaday, “The Delight Song of Tsoai-talee”
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