(Image credit NASA)
On Sunday, feeling smug, and on the heels of my post here I called "Things Ultrarunners Know: Astronomy" I was commenting to the bride on how I think Ultrarunners are more aware of the phases of the moon, as compared to the populace at large.
Specifically I pointed out that the small sliver of the moon (the left side, in fact, from the observer's standpoint) was in fact dwindling as the lunar phase heads towards New Moon on Wednesday. I knew this since I'm always aware of the moon as I run, and knew it had been full moon a couple weeks ago.
So I asked whether she thought that most people even know whether the moon was waxing (getting bigger) or waning (getting smaller).
She quickly deflated me by saying that anybody can tell just by looking at it. When the moon is waning the illuminated part is on the left. When it is waxing, the illuminated part is on the right.
Somehow I missed that that little astronomical nugget. Of course, I will refer you to Bad Astronomy for the easy explanation. As usual, Phil Plait does not disappoint. Just in case, here's another moon phase schematic.