Tidal locking ?

[astromark]

It is with interest that I read of the Earth becomming tidal locked with the Moon. As it is to us. . . When will this happen ?
and how for away will the Moon need to be ?

[Kaptain K]

IIRC (it's been a long time and I might be mistaken)

How long?
2-3 billion years (just about the time the Sun goes red giant).

How far?
350-400 million miles (560-640 million Km).

The month and day will be about 55 (current) days long!

[astromark]

Thanks Kaptain K,. I didn't think I would be surprised. Wikipedia didn't have that bit of vital information. . . .

[korjik]

IIRC (it's been a long time and I might be mistaken)

How long?
2-3 billion years (just about the time the Sun goes red giant).

How far?
350-400 million miles (560-640 million Km).

The month and day will be about 55 (current) days long!

I think you are a couple of orders of magnitude high on the distance.

[cjl]

Yeah - I believe it would be on the order of 3.5-4 million miles away at that point

[Romanus]

Actually, the Moon wouldn't become tidally locked with the Earth until well after the Sun became a red giant and shrank to a white dwarf. In practice though, once the Sun swells to a red supergiant, drag with the (much) thicker interplanetary medium in Earth's vicinity will probably bring the Moon in closer until it collides with the Earth, or breaks up into a ring.

[Planetwatcher]

Or more likely when the Sun reaches that point it will simply consume both the Earth and Moon.

[Kaptain K]

I think you are a couple of orders of magnitude high on the distance.

Yeah, I meant 350-400 thousand miles, not 350-400 million miles!

[peter eldergill]

Perhaps I'm missing the point...I thought the moon already is locked, which is why it doesn't appear to rotate. Have I got the wrong definition?

Pete

[cjl]

The moons rotation is tidally locked with it's orbit - but the earth's rotation is not. This is talking about when the earth's rotation will be tidally locked with the moon.

[NEOWatcher]

Perhaps I'm missing the point...I thought the moon already is locked, which is why it doesn't appear to rotate. Have I got the wrong definition?

Pete

You're halfway to the discussion... (well actually it's a lot less, but I'm going to ignore mass).
The other half is when the Earth only rotates as fast as the moon is going around it. (or the Earth stops rotating from the Moon's point of view)

[peter eldergill]

I didn't know that the Earth appears to rotate if you're on the moon...never thought about it I suppose. Thanks

Pete

[astromark]

For many Melina, humanity had it wrong. Earth is not in the center of the solar system, or galaxy. We have no sensation of our movement. Thus understanding of planetary motion was difficult to sell to the masses.
From the Moon as a viewing platform the same rules apply. Earth would not move across your view. You might with magnification see that it is rotating about once a day., But not at the same speed we see from here. The Moons own motion ( orbit ) would distort the rotation period as viewed from the Moon. . . Whew! From here we see the moon gain about an hour a day across the sky. Have a look at a calender.