Thursday, June 7, 2012


On the morning of June 4, 2012 there was a partial lunar eclipse only visible in the western United States.  As chance would happen, I was visiting Flagstaff, Arizona in route to see the Transit of Venus the very next day.  What an added bonus to be able to see a lunar eclipse followed by a Transit of Venus all within a 36-hour span!

I took some pictures of the eclipse and it got me thinking...  Whenever I teach students about the Moon phases I try to demonstrate that they are not caused by the shadow of the Earth.  The Earth casts a round shadow on the Moon so how could it make a gibbous Moon?  It's impossible - the dark part is curved the wrong way.  In fact when I ask students to draw a gibbous Moon and they give me an eclipsed Moon - ouch, I give them double-points off! 

Below I have a normal gibbous Moon on the left and the eclipsed Moon on the left.  Notice the difference?  Right click on the picture and open it in a new window for a close-up view.

Gibbous Moon                   and                   Partial Lunar Eclipse