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Old 01-30-2010, 08:30 AM   #986
Avalon Senior Member
Join Date: Jan 2009
Location: Massachusetts
Posts: 161
Default Re: Thuban Q&A: (warning longer than normal posts here)

Originally Posted by abraxasinas View Post
Dear firstlook!

If the sun is overhead at noon, it appears smaller against a cyan coloured sky and when the sun is setting, it appears bigger against a reddening sky.

There is more light scattering in the evening because the sun is 'cooler' and 'dimmer' in that less sunlight penetrates the atmosphere. The sunlight must travel further in the apparent orbit of the sun around the sky.
This orbit will increase the ARCLENGTH of the angular chord subtended at the reception point of the sunlight (your eye and retina), compared to the ARCLENGTH subtended or projected where the sun diretly overhead.

This so allows more red light frequencies to get through the atmosphere than the midday sun, which absorbs the red frequencies by gas particles and scatters only the blue frequencies (red light is less energetic than blue light and defined by frequencies).

The MOON reflects the sunlight and so describes the same atmospheric physics and optics as a Mirror.

The closeness of the Moon so becomes the 'greater arclength' projection in addition to 'optical illusions' like Oculomotor micropsia and macropsia . Here is a reference:

For a more technical description of the Moon's ACTUAL apogee-perigee sizes consult the link:

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