Lecture Another practical function of the earth's atmosphere is to act as a giant, hemispherical, blue light bulb. This in turn means that its angular motion in the sky at apogee is slightly faster than its rotation motion, so we can see around one side, and the converse phenomenon happens at apogee.
Tidal force is the difference in the strength of ordinary gravitational force across a body .
Thus, there is a tendency for the difference in gravity, or tidal force, to stretch the earth along the earth-moon line. In this configuration, the gravitational attraction of the moon for the tidal bulges is unbalanced, and produces a braking action, slowing down the earth's rotation. In fact, the length of the day is increasing by .0016 seconds per century. At the same time, to conserve angular momentum, the size of the moon's orbit is increasing by about 4 cm per century, which is turn makes the month longer. After a few billion years, the month will be 47 days long, and so will the earth's day, and one side of the earth will face the moon forever.