Re: astronomy

[Jim Green <JMGreen@sisna.com>]

David Dockstatter muses -

> #14. If the Moon had oceans like the Earth's, what would the tidal 
> effect be like there?  How many high and low tides are there during 
> a "day?"  How would the variations in height compare to those on 
> the Earth?  I think Jim Green wants to answer this one.

I am overcoming my reluctance to enter this issue once more, but David
Bowman is anxious to hear what I have to say (:-), so...

This question seems to presuppose that Earth tides are "caused" by "tidal
bulges", they are NOT!  As I recall, David Boiwman thinks that there are
"small" "tidal bulges" "underneath" the real tides, but I have not been able
to verify this. (David if you have citations, I would be grateful.) There
ARE "tidal FORCES" which bulge a la Newton, but the water does not bulge.

See http://www.sisna.com/users/jmgreen (not JMGreen) for an unfinished
explanation.  I think that this URL still works. (?)

Now, on the Moon, are we going to assume oscillatory ocean basins as on the
Earth?  I think that the driving frequencies would be the same as for the
Earth/Moon, but the Sun/Moon frequencies would be different (and I am not
about to figure them out (:-))  The amplitude of most of the force
components would be different.

All in all there is no way to tell much about Moon tides, if there were Moon
continents.

If the Moon were uniformly aqueous, the explanation would be a bit simpler,
but still not easy.  We would need to know the Moon ocean depth to know how
fast a Moon ocean wave could travel (but surely Moon ocean waves could not
travel sufficiently fast to keep up with the driving forces).  If the Moon
were aqueous, we would need to figure out the resonant frequency of a
typical latitudinal path and then see what driving frequencies might match,
etc, etc, etc, just as needs be done on the Earth.

The Moon does not rotate with respect to the Earth, but it _does_ wobble and
periodically change distance to the Earth and other parameters fluctuate
periodically,  If these frequencies are close to the resonant frequencies of
the Moon ocean basins there could actually be rather high tides.  The Moon
_does_ rotate with respect to the Sun, however, so ....

And there is the damn oscillation of synchronicity we keep talking about,
which might well drive a tidal oscillation:

The Davids are getting uneasy by now. (:-) 

So my short answer: I don't know.

The answer the book expects, however,  is that there woun't be no tides on a
watery Moon, but we all know this, no?   Certainly during the current
synchronicity thread.

Jim Green
JMGreen@sisna.com