This is called a tidal effect, since it’s responsible for the … wait for it … tides. One side of the Earth is slightly closer to the Moon than everything else, so it gets an extra tug, the oceans lifting up trying vainly to reach the moon, and there you go, a tide on that side of the planet. At the exact same time, the ocean on the opposite end of the Earth from the moon gets feeling a little left behind, and tries to float away—a tide appears there, too.8
