Moon Stuff

Tonight will be a Super Moon, a Blue Moon and a Blood Moon, and, for once, it should actually be visible here.

• A Super Moon because the full moon will be closest to Earth in its elliptical orbit.
• A Blue Moon because it is the second full moon of the calendar month.
• A Blood Moon because a partial eclipse will cause the moon to turn reddish-orange just before dawn.

That is a whole lot to be happening in one night, and, as if that wasn't enough, it got me thinking about the moon's orbit of the earth.

How long do you think it takes for the moon to circle the earth?

If your first response was 24 hours (or 25 if you account for the fact that the moon rises a little later each day) you would be spectacularly wrong, since most of what you think you are seeing is the result of the Earth rotating on its axis.  

If, on the other hand, you thought in terms of a 28 day lunar cycle, you would be a lot closer to right.  Actually the time required varies depending on your point of view.  If you're counting relative to the sun, it is more like 29 days and change; relative to the stars, it's just over 27.

If all that seems complicated and a little confusing, that's OK.  We could always go back to when the Earth was flat.