[extropy-chat] Astronomical question

[Mike Lorrey]

--- BillK <pharos at gmail.com> wrote:

> You have to add in the effect of the Sun tides (about half as strong
> as the Moon tides).
> See: <http://www.jal.cc.il.us/~mikolajsawicki/tides_new2.pdf>
> 
> Quote:
> This misalignment of the water spheroid causes the net gravitational
> pull exerted by the water bulges to have a small component along the
> direction of the Moon motion (i.e. a tangential component along the
> Moon's path). As a result, the Moon moves into a higher orbit and
> hence away from the Earth, at the rate of some 4 meters per 100
> years, and the orbital period of the Moon increases. However, since
> the orbital period of the Moon increases at smaller rate than the
> length of the day does, both periods will eventually match. The
> Earth will be then tidally locked with the Moon, and the length of
> the day and the month will both be equal to some 50 present days,
> with the same side of Earth always facing the Moon. Note that the
> same side of the Moon already always faces the Earth, as the tidal
> action of the Earth on the Moon caused the Moon's original spin to
> slow down, and Moon became
> tidally locked with the Earth a long time ago, in the sense that the
> Moon spins once on it's axis for each revolution around the Earth.

Since we are talking about sun-tide issues here, will the earth be
moving in or out from the sun in its orbit? Will the Sun cause the
Moon's orbit to become eccentric as it gets farther and farther from
the earth? Will the Moon eventually reach one of the Earth-Sun Lagrange
points?

> 
> Once the Earth becomes tidally locked with the Moon, the solar tides
> will tend to slow the Earth's rotation even more, so the day will be
> longer than the month and the Moon will rise
> in the West and set in the East. The water spheroid generated by the
> Sun will cause the high tide to appear earlier than the time of
> highest moon, a situation exactly opposite to that of Fig. 2. Then
> the tidal force of Earth on the Moon will pull the Moon into a lower
> orbit and eventually inside the Roche limit (18500 km), whereupon
> the Moon will disintegrate, producing a ring around the Earth.

Now I finally have an environmental group I can relate to: "Save the
Moon!" Given also the present environmental movement's obsession with
KEEPING THINGS AS THEY ARE, FOREVER, BECAUSE THAT IS NATURAL, Save The
Moon will be dedicated to keeping the moon in its present orbit and
will work with it's sister organization, the Association To Preserve
The Twenty Four Hour Day, in figuring out how to keep the Earth
spinning at the same rate, forever. We are obviously going to need a
LOT of federal funding and tax-deductible donations to solve these
problems, starting with the construction of a lunar base and massive
solar power farms on the moon to power gigantic mass drivers. We can
kick it off with a big telethon called "MoonAid".
Perhaps Earth's spin could be preserved with some Skyhooks anchored to
some asteroids....

=====
Mike Lorrey
Vice-Chair, 2nd District, Libertarian Party of NH
"Necessity is the plea for every infringement of human freedom.
It is the argument of tyrants; it is the creed of slaves."
                                      -William Pitt (1759-1806) 
Blog: http://www.xanga.com/home.aspx?user=Sadomikeyism

__________________________________________________
Do You Yahoo!?
Tired of spam?  Yahoo! Mail has the best spam protection around 
http://mail.yahoo.com