PDA

View Full Version : Moon phases



Snydley
2003-Oct-13, 11:07 PM
In the discussion about phases of the moon, the book says that the phases move the opposite direction in the southern hemisphere than in the northern hemisphere. Could someone explain that to me? At first glance it sounds ok, but upon further consideration I can't figure it out.

If that were true, then it would seem that the moon phases would necessarily move up and down (rather than left and right) when you're on the equator or the poles. You'd also be able to accurately estimate your latitude by observing the tilt of the phase. And I've never heard of either.

Thanks.

Pinemarten
2003-Oct-13, 11:37 PM
I think they are the same, but everyone in the SH is standing upside down.
If we stood on our heads in the NH we would see the same as them. :wink:

SeanF
2003-Oct-14, 02:38 PM
Welcome to the BABB, Snydley!

It would theoretically be possible to use the Moon's phases to figure your latitude, but it would be complicated by the fact that the Moon's orbit is not equatorial. Sometimes it's "above" the equator and sometimes it's "below." You would need to know at what point in its orbit the Moon is currently to convert its phase angle to your latitude.

The moon phases do generally move up and down when you're on the equator (and generally straight left and right at the poles), but (again because of the tilt of the Moon's orbit) they're not always the same.