Q: Why do all celestial objects spin on their axes?
A: Imagine a cloud of dust in space that will eventually coalesce into an asteroid, a planet or a star. It is bound to rotate slowly because the forces of gravity operating on it from different directions are not equal. As gravity pulls the particles in the cloud toward a common center, many skim by it and spiral around the center. When each particle finally becomes part of the forming body, the particle adds its own angular momentum to the body’s, producing spin. The spin of celestial bodies is slowing as a result of friction, but the rate of slowing is too small to be observed directly.