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but I've recently read (wish I remembered where) that it's no longer expected to work that way. Possibly because it takes so long for the outbound leg that the sun does its red giant bit in the meantime, which seems likely to throw a monkey wrench into the whole scenario... but I don't know if that's the right explanation.
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Well that's *certainly* true. I don't know if that's the explanation you were thinking of, but it's definitely true.
Don Smith
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Well if the Moon is in geosynch orbit at 432,000km (12 x 36,000km) for a 42 hour day and it takes more than 3 billion years to reach that point, it would likely be very near there when the Sun becomes a red giant. At that distance, the escape velocty from the Earth isn't terribly great, so I have little doubt that the Moon would be stripped from the Earth, even if the Earth manages to survive the Sun's red giant phase.
Of course, people living on the tropical moon Europa would not care much about such a lifeless world as the Earth by then, especially since the lifeless Mercury and Venus would have been consumed by the Sun long ago.