Cumberland Times-News

Bob Doyle - Astronomy

August 25, 2012

The ‘Blue Moon’ and other lunar fantasies

This Friday, Aug. 31, will feature August’s second full moon. (The moon will look very full on Thursday night as the actual time of full moon is 9:57 a.m. on Friday.)

This second full moon is called a “Blue Moon.” Two full moons tend to occur in the longer months of 31 days. The moon’s phase cycle (from full moon to full moon) is 29.5 days.

We had a full moon on Aug. 1, making the second full moon possible. We have a “Blue Moon” about every three years. Next month’s full moon will occur on very late in the evening of Sept. 29. This is the “Harvest Moon.”

There’s a fascinating book about the Moon by Bernd Brunner, covering both science and myth. “Moon – A Brief History” was published by Yale University Press in 2010 with ISBN 978-0-300-17769-5 (paperback).

Can the moon actually appear blue? As Brunner relates, after a volcanic eruption, there may be a large amount of tiny particles about one micron wide (millionth of a meter or 0.0000004 inches) injected into the stratosphere.

Since this particle size is close to the wavelength of red light (0.7 microns), more of the longer waves of moonlight (red, orange and yellow) are scattered away.

This would make the moonlight we see mostly the shorter color waves (green, blue). Such “blue moons” were seen for several years following the 1883 eruption of Krakatoa on an island of Southeast Asia.

The Chuckchee Shamans (medicine men) from northeast Siberia purposely exposed themselves to full moon, instilling them with magical powers. Some African tribes dance by the light of the full moon.

The Aztecs were fearful when the crescent moon disappeared in the glare of the sunrise, prompting them to pray for its return. So a few days later, when a narrow crescent moon was again seen in the western dusk, the Aztecs celebrated.

Eclipses by the moon (solar) and of the sun (lunar) were feared by ancient people. The Maasai of East Africa throw sand into the air during a solar eclipse. Some Native Americans shoot flaming arrows at the darkened moon during a lunar eclipse.

There is a charming story about the man in the moon. (When full, the light and dark areas of the moon form a crude pattern of a human face. Others claim to see a lady in the moon, while many see a rabbit on the moon.)

In a German myth, a man went to gather wood on Sunday, the biblical day of rest. The man never came back. His worried family saw his face, peering at them from the moon.

   Photometric (light sensing) measurements reveal that the full moon shines with only 1/400,000 of the intensity of the sun. The full moon is 25 times as bright as the half full moon (the evening moon that resembles a letter D).

At full moon, the sun is shining straight down on the moon and there are few shadows. At half full, there are a lot of shadows on the moon and the illuminated part of the moon we see is receiving sunlight at a low angle to the vertical.

EVENING SIGHTS THIS WEEK: Since moonlight dominates this week’s evening sky, it is best to focus on the brighter stars.

Nearly overhead is the bright white-blue star Vega. Vega is 25 light years away, meaning that its light we see tonight left that star twenty five years ago (in 1987).

The second brightest star is Arcturus, a bright golden star in the west. Follow the curve of the Big Dipper’s handle outward and in one Dipper’s length, you will come to Arcturus.

The light of this star has taken 36 years to reach us. So we see Arcturus as it was in 1976, our bicentennial year (200 years since the Declaration of Independence).

Bob Doyle invites any readers comments and questions. E-mail him at rdoyle@frostburg.edu . He is available as a speaker on his column topics.

1
Text Only
Bob Doyle - Astronomy
  • FSU Planetarium has new outreach program

    Several years ago, the FSU planetarium acquired an iPad. Months later, we purchased an iPad projector with necessary cables. I purchased a number of astronomical apps this year for the iPad. So I’m interested in visiting schools in this county to teach the stars and planets to classes. The astronomical apps allow you to survey the current evening night sky and show the planets, bright stars and star groups. One of the apps shows the planets close up with wonderful surface detail (as if you were cruising by in a spaceship). The apps I’ll be using can be purchased from the iTunes app store for a few dollars.

    July 27, 2014

  • It’s hotter here than in D.C. or Baltimore

    At this time of the year, the weather is a frequent subject of conversation, particularly the temperatures. We are now in the “Dog Days,” usually the hottest days of the year. The term comes from our sun appearing to be near the “Dog Star” (Sirius) and the “Little Dog Star” (Procyon). In reality, the sun is now about 94.5 million miles away while Sirius is 8.6 light years away with Procyon at 11 light years distance. Sunlight takes only 507 seconds to reach us, while the two dog stars’ light takes about a decade to travel to our eyes. So our sun is in the same direction (but not distance) as these two bright winter evening stars.

    July 20, 2014

  • Fronts, highs, lows determine weather

    Weather news on television and internet focus on violent weather, extreme temperatures and flooding.

    July 13, 2014

  • A long and winding road faces our food

    Last week’s column dealt with organs you can do without, our DNA (molecular blueprint for our bodies) and hair. My reference is “Body: Discover What’s Beneath Your Skin,” a Miles Kelly Book, written by John Farndon and Nicki Lampon and published in 2010. This column will consider finger and toe nails, breathing and coughing, saliva, mucus and your food’s long and torturous journey. Most cities and mid sized towns have nail shops where you can have your finger nails and toe nails adorned. Nail painting can be traced back 5,000 years.

    July 6, 2014

  • Here’s a look at what goes on inside you

    In high school, my favorite science course was biology. I can remember Mr. Munley in his wheelchair. Our class went on a field trip to the University of Miami Medical School where we saw the cadavers used by the medical students.

    June 28, 2014

  • Moon-watching easy when you know how

    Long before the first writing (scratches on clay tablets) appeared, our early ancestors noticed that the moon went through a regular cycle of shapes in about 30 days.

    June 21, 2014

  • Here’s how you can tell the stars, planets

    How can one tell one star from another at night? It’s a matter of knowing the sky areas (constellations).

    June 15, 2014

  • Smithsonian guide to stars is a good one

    At a local book store, I yielded to temptation and bought “Stars and Planets,” a Smithsonian Nature Guide written by four authors. Dinwoodie, Gater, Sparrow and Stott. It’s another Dorling Kindersley product with ISBN 978-0-7566-9040-3 and a 2012 copyright. “Stars and Planets” is a trade size paperback that is beautifully illustrated with appealing diagrams. “Stars and Planets” begins with the biggest topic, the Universe. There is a striking visual showing the known universe on the hugest scale, a delicate lacework of superclusters of galaxies with large voids. It resembles a bubble bath!

    June 8, 2014

  • Think a little more and be less frazzled

    Last Sunday’s column dealt with using technology carefully in education. What about technology in everyday life? There is a marvelous book “The Thinking Life,” by P.M. Forni, of The Johns Hopkins University which addresses this issue as well as timeless suggestions for living by Greek and Roman thinkers. “The Thinking Life: How To Thrive in the Age of Distraction” was published by St. Martin’s Press in 2011 with ISBN 978-0-312-62571-9. Dr. Forni also wrote “Choosing Civility” and “The Civility Solution”.

    May 25, 2014

  • Technology helps with learning, but take care

    Since I have been involved in teaching, two different technologies have been applied to learning at the secondary and collegiate level. The first was video (from videocassettes to DVDs) where a student or class might watch a presentation of some historical event, or a set of scientific principles or even a simulated exploration of the human body.

    May 18, 2014

Latest news
Facebook
Must Read
House Ads