Hell David,

->> The length of the year (as measured against the atomic clock
->> that we use now is not affected. So if one measures age in
->> years, there is no effect.

The lenght of the year is not affected by tidal friction casued by the moon.

 > Actually, there *is* an effect.

Well you'r right of course in that the solar tides have a similar effect on
the earth orbit around the sun.

 > The sun raises tides on both the Earth

yes and although smaller (about 1/3) than the moon's tide, it is not
negligible. Wittness spring tide and neap tide.

 > and the Moon,

The moon has no oceans, so tidal friction has to come from the deformation
of the solid body. Plus that the moon has little angular momentum by
rotation anyway. i think we can safely label this as neglegible.

 > and the friction produced as they rotate transfers
 > angular momentum and energy from the rotations to the orbital
 > motion of the Earth-Moon system around the Sun. As a result,
 > the Earth and Moon are slowly moving outward from the Sun, and
 > the length of a year is increasing.

True. In theory....

 > It's a tiny effect, though, since the energy and angular
 > momentum that are involved in Earth's orbital motion are huge
 > compared with the amounts in its rotation.

Yep.

 > Let's see... The angular momentum in Earth's rotation is, in
 > units in which its mass is unity and the unit of time
 > is a day, mr^2w, or r^2, or about 2e7, with kilometres as the
[...]
 > Transferring the whole amount in the rotation to the orbital
 > motion would make hardly any difference. The length of the
 > year would be increased by only a few seconds.

So we will probably never be able to measure this effect as there are other
forces acting on the earth orbit that are much larger.

Cheers, Michiel

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