Earth's gravity on the Moon

[Halmyre]

prand said:

FarmyardPants said:

But since the moon is “tidally locked”, it is permanently high tide, as it were, on the side facing the Earth (and also the opposite side). That said, the moon is not in a circular orbit so the effect of Earth’s gravity varies causing the bulging of the moon to vary slightly during the month (and also Earth’s tides to vary of course).

Ah I see, the moon isn't spinning any more which means the motion effect from tides is not really happening like it does on earth, so the effects are not so pronounced, not like that moon around Jupiter made up of a liquid interior that continually erupts through the moon's crust due to the combination of gravity and movement around the gas giant.

The moon *does* spin, once every 27 and a bit days, otherwise its entire surface would be observable from earth - although an observer in the UK would always see the same side, and an observer in Australia would always see the opposite side.

[Eric Mc]

prand said:

Ah I see, the moon isn't spinning any more which means the motion effect from tides is not really happening like it does on earth, so the effects are not so pronounced, not like that moon around Jupiter made up of a liquid interior that continually erupts through the moon's crust due to the combination of gravity and movement around the gas giant.

The moons around Jupiter are also tidally locked to their parent planets i.e. they keep the same face turned towards the planet. The mechanism that generates heat within these moons is the interaction between the gravity of Jupiter and the other moons the orbit inside and outside of each other. They are all yanking on each other to a greater or lesser extent which causes the moons to flex and create heat within their interiors.

[AshVX220]

Is the moon tidally locked because more of its mass is facing the earth or just because any spin it has is exactly the same speed it takes to orbit the earth?

[Eric Mc]

AshVX220 said:

Is the moon tidally locked because more of its mass is facing the earth or just because any spin it has is exactly the same speed it takes to orbit the earth?

The latter is the definition of tidally locked.

If you look throughout the solar system you will find many examples of bodies which have become tidally locked to their parent planet.

Some of the exo planets that have been discovered orbiting other stars are likely to be tidally locked to those stars.