Well, think about how the tides will be affected when the moon moves farther away. If the moon first started off very close the earth, we would have more tsunamis. (Scientists have found that the moon has possibly been closer to earth long ago.) While it moves away, soon there will no longer be many tides.
This is an example of state change from solid to liquid.
That creates a secondary color
Period = (1) / (frequency)
= (1) / (20/sec)
= 1/20 sec
