The Moon's rotation is tidally locked relative to the Earth so that it always presents the same face towards us. This is due to the Earth's greater gravity pulling against the rotation of the Moon on its own axis.
The Moon does rotate on its own axis still, it makes one complete rotation for every orbit around the Earth, i.e. one day on the Moon is the same length of time it takes to make one orbit around the Earth (about one month). You can demonstrate this by drawing a dot on a ball and rotating it about an object so that the dot always faces the object. You will notice that the dot must make one rotation about the axis of the ball for this to occur.
This does mean of course that there is no 'dark side' of the Moon either. All parts of the Moon (apart from the bottoms of a few craters near the poles) see sunlight at some point during a lunar day. e.g. when the Moon is New (directly between us and the Sun) the side that we cannot see is fully sunlit, the side facing us is in darkness.
Because the Moon's orbit is not perfectly circular we can actually see 'around the corners' as the Moon orbits the Earth. These libration effects mean that the Moon presents a slightly different face to us at any given time. We are therefore able to see 59% of the Moon's total surface from the Earth.
The moon is tidally locked to the Earth. The forces between the Earth and the moon have gradually decelerated the moon until its rotation period is equal to its revolution period.
The Moon does rotate on its own axis still, it makes one complete rotation for every orbit around the Earth, i.e. one day on the Moon is the same length of time it takes to make one orbit around the Earth (about one month). You can demonstrate this by drawing a dot on a ball and rotating it about an object so that the dot always faces the object. You will notice that the dot must make one rotation about the axis of the ball for this to occur.
This does mean of course that there is no 'dark side' of the Moon either. All parts of the Moon (apart from the bottoms of a few craters near the poles) see sunlight at some point during a lunar day. e.g. when the Moon is New (directly between us and the Sun) the side that we cannot see is fully sunlit, the side facing us is in darkness.
Because the Moon's orbit is not perfectly circular we can actually see 'around the corners' as the Moon orbits the Earth. These libration effects mean that the Moon presents a slightly different face to us at any given time. We are therefore able to see 59% of the Moon's total surface from the Earth.
The moon is tidally locked to the Earth. The forces between the Earth and the moon have gradually decelerated the moon until its rotation period is equal to its revolution period.
No comments:
Post a Comment