Blame it on the moon
This summer, when you are at the seashore and you have to move your beach blanket because the waves are getting closer, you can blame it on the moon, our nearest celestial neighbor. The regular daily and monthly rhythms of the moon affect our planet’s cycles, notably tides.
Tides occur because the moon’s gravitational force pulls on the water in the oceans, causing the oceans to bulge out in the direction of the moon. Another bulge occurs on the opposite side of Earth because Earth is also being pulled toward the moon and away from the water on the far side. Because Earth is rotating while this is happening and the moon is moving in its orbit around Earth, two nearly equal high and low tides occur each day.
During a new or full moon, when the moon is relatively close to Earth, the tidal effects of the sun and moon create especially high tides called spring tides (which comes from the German word “springen,” meaning to rise up). People who live near the ocean worry about storms that occur during this period because of the destruction the high waves can create. At the time of the first and last quarter moon, the effects of the sun and moon are not substantial, and we have neap tides, when high and low tides differ least.
Tidal forces also affect the solid Earth, although not as dramatically as the oceans. Recent satellite measurements of ocean tides allowed scientists to accurately measure the tidal bulge in Earth’s crust. They discovered a tidal bulge of almost 8 inches high existing in the solid Earth under and across from the moon.
Tidal forces are also important in understanding many astrophysical phenomena, including volcanism, planetary ring systems, accretion disks around neutron stars and black holes.