Once in a Blue Moon

Well, it is TUSAL time again  - the second time this month.  Two full moons in a month is called a Blue Moon.  I did a bit of research and while we all know that the moon is not really blue but "Once upon a time....."

There was a time, not long ago, when people saw blue moons almost every night. Full moons, half moons, crescent moons--they were all blue, except some nights when they were green.

The time was 1883, the year an Indonesian volcano named Krakatoa exploded. Scientists liken the blast to a 100-megaton nuclear bomb. Fully 600 km away, people heard the noise as loud as a cannon shot. Plumes of ash rose to the very top of Earth's atmosphere. And the moon turned blue.

Krakatoa's ash is the reason. Some of the ash-clouds were filled with particles about 1 micron (one millionth of a meter) wide--the right size to strongly scatter red light, while allowing other colors to pass. White moonbeams shining through the clouds emerged blue, and sometimes green.

Blue moons persisted for years after the eruption. People also saw lavender suns and, for the first time, noctilucent clouds. The ash caused "such vivid red sunsets that fire engines were called out in New York, Poughkeepsie, and New Haven to quench the apparent conflagration," according to volcanologist Scott Rowland at the University of Hawaii.

Above: Still smoldering after all these years: a recent picture of Krakatoa. Credit: Robert W. Decker of Volcano World. [More]

Other less potent volcanos have turned the moon blue, too. People saw blue moons in 1983, for instance, after the eruption of the El Chichon volcano in Mexico. And there are reports of blue moons caused by Mt. St. Helens in 1980 and Mount Pinatubo in 1991.

The key to a blue moon is having in the air lots of particles slightly wider than the wavelength of red light (0.7 micron)--and no other sizes present. This is rare, but volcanoes sometimes spit out such clouds, as do forest fires:

"On September 23, 1950, several muskeg fires that had been quietly smoldering for several years in Alberta suddenly blew up into major--and very smoky--fires," writes physics professor Sue Ann Bowling of the University of Alaska. "Winds carried the smoke eastward and southward with unusual speed, and the conditions of the fire produced large quantities of oily droplets of just the right size (about 1 micron in diameter) to scatter red and yellow light. Wherever the smoke cleared enough so that the sun was visible, it was lavender or blue. Ontario and much of the east coast of the U.S. were affected by the following day, but the smoke kept going. Two days later, observers in England reported an indigo sun in smoke-dimmed skies, followed by an equally blue moon that evening."

Right: Smoke from forest fires can cause blue moons, too. Photo credit: John McColgan of the Bureau of Land Management, Alaska Fire Service.

But I digress, you really just want to see my TUSAL report, don't you? lol!

Well, here it is:

Home orts on the left and train orts on the right.

... and here is all of this year's orts inside my coffee pot - don't you just love the translucence of the porcelain?

Well, that is all for me today - off to the travel agent shortly to book train tickets from Milan to Lake Como for our trip - doesn't that sound exciting?  But then it will be the supermarket for me (less exciting), some stitching and then some water aerobics.

hugs,

P.S. Now, don't forget to join in my Grow Your Party Giveaway fun on this post here or visit all of the other partygoers via Vicki's blog here.