Tides and the 2,000-Mile Man What causes the seas to rise…

““Tides and the 2,000-Mile Man What causes the seas to rise and fall as if they were breathing two big breaths every day? It’s the Moon, of course, but how does it do it, and why twice a day? I will explain, but first let me tell you about the fall of the 2,000-Mile Man. Imagine the 2,000-Mile Man—a giant who measures 2,000 miles from the tip of his head to the bottoms of his feet—as he falls, feet-first, from outer space toward the Earth. Far out in outer space, gravity is weak—so weak that he feels nothing. But as he gets closer to the Earth, strange sensations arise in his long body—sensations not of falling but of being stretched. The problem is not the giant’s overall acceleration toward the Earth. The cause of his discomfort is that gravity is not uniform throughout space. Far from the Earth, it is almost entirely absent. But as he draws closer, the pull of gravity increases. For the 2,000-Mile Man, this presents difficulties even while he is in free fall. The poor man is so tall that the pull on his feet is much stronger than the pull on his head. The net effect is an uncomfortable feeling that his head and feet are being pulled in opposite directions. Perhaps he can avoid being stretched by falling in a horizontal position, legs and head at the””

— Leonard Susskind