HoSV Astronomy:  Bad Moon Rising

I see the bad moon rising

    I see trouble on the way

I see earthquakes and lightnin’

    I see bad times today

Don’t go around tonight

    Well, it’s bound to take your life

There’s a bad moon on the rise

                               Creedence Clearwater Revival

For astronomy geeks the term “Bad Moon” is less dramatic and far less ominous than it might sound.  It refers not to a portent of destruction but rather to the moon depicted in an improper location or in an improper phase.   

***SPOILER ALERT***

In the movie Apocalypto our hero avoids execution and escapes his captors thanks to the distraction provided by a fortuitous total eclipse of the sun.  Later that night we see him under the light of a full moon.  Less that 24 hours after an solar eclipse the moon’s phase would be new not full.  Bad moon!  However a far more egregious error is that the movie portrays the collapse of the Mayan civilization and ends with the arrival of the conquistadors.  The collapse of Teotihuacan took place in the year 900.   Spanish explorers didn’t reach the New World until the late 1400s.  That’s an error of half a millennia no less. 

***END SPOILER ALERT***

Another example of a bad moon is the book Harold and the Purple Crayon.  Little Harold goes for an evening stroll under the crescent moon.   Since our young hero is a northern hemisphere boy the rising moon would appear in the southeast.  With the moon over his left shoulder Harold would be facing the southwest; the direction of the recently set sun.  Therefore the crescent moon should curve to the right and not to the left as shown in the drawing.  Bad moon!  

English is read from left to right and top to bottom unlike Hebrew that is read from right to left.  Without giving it any thought the illustrated action in our comic books and story books runs from left to right just as we read.  I happened across a Hebrew translation of Harold and noticed that the art work had been converted to mirror images to make the flow of action more natural for the reader.  With this adjustment the bad moon was transformed into a “good” moon.  But how can we be sure that Harold lives north of the equator?  By careful study of vintage funny pages we see that Harold is in reality Crockett Johnson’s Barnaby, a boy who lived in the US during World War 2. 

If there are bad moons are there also bad Earths?  Indeed there are.  The most famous example is the Apollo 11 mission patch.  If the Eagle was landing at Tranquility Base on July 20th 1969 the gibbous Earth would be orientated such that the greatest illumination was from above as opposed to from the right as shown.  Bad Earth!