Saturday, October 7, 2006

harvest moon

tonight's full moon is dubbed the "harvest moon" and is the full moon that occurs nearest to the autumnal equinox.

image above from astronomy picture of the day

this moon signifies the beginning of the harvest season for many cultures in the northern hemishpere.

you may have noticed at some point that when the moon is close to the horizon, just after sunset, it appears larger than it usually looks when it's high in the sky. a common misconception is that this is mostly because we view the moon near familiar objects like trees or houses, etc... this is not the case as explained by Donald E. Simanek, here.

i also remember thinking when i was a kid that the harvest moon was my favorite because it appeared to have an orange tint. it turns out that this is true for the same reason that the sky is blue! you can follow that link for a full description (or this one by the bad astronomer. briefly, it is because the light reflected off the moon travels thru more of the earth's atmosphere to reach us when the moon is on the horizon. the particles in the atmosphere scatter the photons of light as they travel, preferentially scattering the higher frequency photons (blue, green and yellow), leaving the photons with frequencies corresponding to orange and red to meet our eyes. this effect become more apparent when there is more pollution or other particles in the atmosphere, so the degree of orange-ness differs depending on where on earth you are!

here is some other intersting stuff about the full moon.

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