"Marshall Dudley" wrote in message
...


Your are right. I had no idea that I was taught wrong in school about mercury
in the early 60's. But I checked and sure enough the textbooks back then do
not agree with what I find now.

I was also taught the moon is locked in it's rotation with one face toward the
earth at all times. That one I believe still stands.


Not exactly. Since the Moon's orbit is slightly elliptical,
and so speeds and slows slightly in its path as it does,
the face it presents oscillates slightly too. This effect
is called "libration". It allows us to view, over time,
slightly more than 50% of the Moon. Of course, there's
also the fact that the Moon's orbit is inclined to the
equator, so from our vantage point we can also see a bit
above and below its poles throughout a month.