Sun moon basic question

[Tinners]

Something that always bothered me but I could never figure it out

Why does it appear that the moons reflection doesn't line up with the suns postion.

For example at around 3.30pm the sun was close to the horizon but the reflection on the moon - drawing a line through the moon from the middle of the dark edge to the middle of the illuminated edge - "points" towards a light source much higher in the sky (well above 30')

[The Warthog]

It's a little bit difficult to visualize, but it's because the sun isn't illuminating the moon from the side, but from behind. Imagine, if you will, holding up a ball at arm's length towards a bright light source 700 feet away (roughly the relative distances of the earth and moon.) A small displacement in the position of the ball will make a big difference to what part of the ball is illuminated from your point of view. The position of the sun beside the moon is an illusion; the sun is illuminating the moon from a different direction than what appears to the eye.

[Tinners]

Not sure I follow that.

Surely the illuminated face "points" to the suns postion at least in one diamention irrespective of where

we view it from. For example drawing a line across the points of the teminator (Yellow) and using that

as a guide to the suns position (Red line) in the sky

[The Warthog]

As I said, it's hard to visualize.

[barkis]

Perhaps this simulation will help. You can control the speed by the slider top right.

It is easy to use and shows the the moons phase according to it's position of orbit around earth.

You need Java enabled to run it unfortunately.

Ron.

http://jove.geol.niu.edu/faculty/stoddard/JAVA/moonphase.html