引力天文学

例句：

1. 1. Gravitational forces are responsible for the movement of objects in space.
   引力是物体在空间中运动的原因。
2. 2.The gravitational pull of the Earth is what keeps us on the surface of the planet.
   地球的引力作用使我们保持在星球表面。
3. 3. The moon's gravity is so strong that it can hold a manned spacecraft in orbit around the Earth.
   月球的引力非常强大，可以保持载人航天器围绕地球运行。