That's a great question. Things on the Earth's surface sink or falldue to the Earth's gravity, which pulls everything toward the centerof the planet. The entire Earth is balanced, however, so it isn'tbeing pulled one way or another. Instead, gravity is what holds theplanet together so it doesn't just fall apart. The Earth also feelsthe Sun's gravity and is pulled toward it--that's why the Earth orbitsthe Sun and doesn't just wander through space.