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A Lazy Sun and a Harvest Moon

What one notices about this particular dawn is both the gentleness of its breakage -- the way it's taking its jolly time to get light outside (which we can interpret as a sign that we're getting into the months where the sun just kind of angles up over the horizon like it wants to get away with something without anyone noticing) -- and the crickets. Lots of crickets. The crickets are much louder than the birds. The birds are worrying about this and that, and hectoring one another, but the crickets are almost cicada-like in their intensity. This is possibly because they are, indeed, cicadas. But I think they are crickets, plotting to invade my basement as temperatures drop.

[Pause while leaving computer to check on sky again.]

OK, not much happening there. It's not a crisp fall morning. No autumnal clouds high in the sky. There is no opportunity to show off by using the word "lenticular." There is discernible humidity, but nothing unpleasant. There are a few cloudlike structures in the distance but they might simply be smoke from explosions. Though it is now light outside, the sun still hasn't made an appearance, and I'll be danged if I'm going to wait around for it. Let's move onward.

[Checks sky again.]

Oh, there it is. Good. Was worried that it'd be another sun-won't-rise morning.

[Let's just hope the news is better today than it has been in recent days.]

Curmudgeon passed along a document the other day about the upcoming Harvest Moon, which will rise on the evening of Oct. 6 unless something really goes bollywackers in the night sky. [Via Google is appears the author is a certain Dr. Tony Phillips.]

'Not so long ago, before electric lights, farmers relied on moonlight to harvest autumn crops. With everything ripening at once, there was too much work to to do to stop at sundown. A bright full moon--a "Harvest Moon"--allowed work to continue into the night.

'The moonlight was welcome, but as any farmer could tell you, it was strange stuff. How so? See for yourself. The Harvest Moon of 2006 rises on October 6th, and if you pay attention, you may notice a few puzzling things:

'1. Moonlight steals color from whatever it touches. Regard a rose. In full moonlight, the flower is brightly lit and even casts a shadow, but the red is gone, replaced by shades of gray. In fact, the whole landscape is that way. It's a bit like seeing the world through an old black and white TV set.
"Moon gardens" turn this 1950s-quality of moonlight to advantage. White or silver flowers that bloom at night are both fragrant and vivid beneath a full moon. Favorites include Four-O'clocks, Moonflower Vines, Angel's Trumpets--but seldom red roses.

'2. If you stare at the gray landscape long enough, it turns blue. The best place to see this effect, called the "blueshift" or "Purkinje shift" after the 19th century scientist Johannes Purkinje who first described it, is in the countryside far from artificial lights. As your eyes become maximally dark adapted, the blue appears. Film producers often put a blue filter over the lens when filming night scenes to create a more natural feel, and artists add blue to paintings of nightscapes for the same reason. Yet if you look up at the full moon, it is certainly not blue. (Note: Fine ash from volcanoes or forest fires can turn moons blue, but that's another story.)

'3. Moonlight won't let you read. Open a book beneath the full moon. At first glance, the page seems bright enough. Yet when you try to make out the words, you can't. Moreover, if you stare too long at a word it might fade away. Moonlight not only blurs your vision but also makes a little blind spot. (Another note: As with all things human, there are exceptions. Some people have extra-sensitive cones or an extra helping of rods that do allow them to read in the brightest moonlight.)'

There's more, about rods and cones, the fovea, the blueshift, but that's probably enough lunacy for this particular item.

From ScienceTim we received this annotation:

"As it gets around to mentioning at the end, our color vision is not as sensitive as our contrast vision, which would be the main reason that flowers lose color in moonlight. That, and I think that flowers also have a significant fluorescent component in their pigments. Since moonlight is reflected light, and UV light has very poor reflectivity from most surfaces, there wouldn't be any UV light to drive the fluorescence. Amateur astronomers use 'averted vision' to locate faint big things like comets and distant star clusters -- the light can be detected with peripheral vision, whereas it just disappears when you look right at it."

By Joel Achenbach  |  October 4, 2006; 6:02 AM ET
 
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