Thursday, December 31, 2009

Once in a Blue Moon

Four hundred years ago, in Galileo’s time, a once-in-a-blue-moon event would occur, well, never, as the phrase referred to something so absurd as to be nonexistent. It would occur with the same frequency as, for example, hell freezing over.

In the 20th century, the expression came to mean a very rare event that, nonetheless, could actually happen. Astronomically speaking, Blue Moon came to refer to the second Full Moon in a calendar month, which typically occurs every two and a half years.

The Full Moon, with a few drops of artificial color

Tonight, on New Year’s Eve, as we leave behind the “oughts” of our brave new century and enter the “tens,” we can enjoy a view of a Blue Moon: the second Full Moon this month and the first Blue Moon to occur on New Year’s Eve since the close of 1990, nearly twenty years ago. Tonight the brilliant Moon waxes poetic, in what seems a perfect close to 2009, the International Year of Astronomy.


Once in a blue moon, those of us who evangelize for astronomy get an opportunity to wear our hearts on our sleeves and have it fully sanctioned by such august bodies as the International Astronomical Union and the United Nations. The International Year of Astronomy, the quadricentennial of Galileo’s achievement, was certainly such an opportunity--if you seized it.

As I take stock of this past year, I feel gratitude for having been able to participate in communicating astronomy to the public during IYA--for having had the time, the resources, and the invaluable support of others in order to do so. It was an unforgettable adventure.

With a little help from my friends, I co-instructed weekend workshops in astronomy at a National Wildlife Refuge; gave slide show presentations at libraries; taught astronomy to gun-slinging women at an NRA facility; gave people views through my telescope at museums and public spaces; co-organized a free public astronomy event for girls; conceptualized a nonprofit science education organization which will launch next year; and began writing a second astronomy-related book (because working on one wasn’t challenging enough?!) I indulged myself in paying my passion forward, for whatever it may be worth.

Thank you to all who patronize my blog, especially those gracious individuals who leave comments. Thank you to my fellow astronomy enthusiasts who generously offered topic suggestions for this year’s “Astronomy Essentials” feature: Aileen O’Catherine, Barry Spletzer, Bob Havlen, David Nelson Blair, and Linda Hixon.

And thank you to everyone who this year said to me, “This is the first time I’ve looked through a telescope!” or “I never understood before what the Moon’s phases were!” or “Wow, look at those craters!”

Once in a blue moon, your heart is full.

Astronomy Essential: The Moon is visible during the day, nearly every day.

We tend to think of the Moon as a nighttime object, probably because its brightness is amplified against the dark backdrop of the night sky.

But, if you remember to look for it, you can find the Moon in the daytime sky. It’s visible with the naked eye for part of each day, nearly every day. The only times during its month-long cycle that the Moon doesn’t grace the daytime sky are: 1) Full Moon, when the Moon rises at sunset and sets at sunrise, and 2) a day or two surrounding New Moon, when it’s too close to the Sun in the daytime sky and is masked by the Sun’s glare. (Never ever look directly at the Sun!)

We see the Moon during the day both because it is so bright and close, and because it is in orbit around us and its “window of visibility” is always shifting relative to Earth’s day/night cycle.