When will the moon finally pull out of the Earth's orbit?

Question

I read in a book that says the moon is moving away from our earth about 3 cm each year... So when will it finally "fly" away?

Answer 1

The Sun is expected to expand into a red giant in about 5 billion years. How far away will the Moon be when that happens? If we assume a constant rate of recession and multiply 3cm by 5 billion, we get 15 billion cm which is 150,000 km. The Moon is presently at 384,000 km so it's distance will only have increased by about 40% by the time the expansion of the Sun envelops the Earth - Moon system. This increased distance of the Moon is still well within the Earth's sphere of gravitational influence, so it won't fly away.

Answer 2

It won't.

The Moon's recession is an effect of tidal forces. The same forces are slowing down the Earth. It's an effect of the mutual gravitational atttraction between the two objects. The end point of that interaction is tidal locking of both bodies. The Earth will rotate at the same rate as the Moon orbits, so will present one face only to the Moon. When that happens the Moon will stop moving away and may start moving back in.

However, best estimates suggest that the Sun will burn out before that stage is reached anyway. Either way, we will not lose the Moon.

Answer 3

the moon moves away because it creates tides with gravity which are pulled ahead of the moon by earths spin on its axis and then the tides gravity pulls on the moon accelerating the moon to a higher orbit.

and it will be a long time till it 'flies off' probally 1million years or so

also the moon acts as a planetary gyro stabiliser for the earth stabilising its spin on its axis