Two Uranus moons can crash into each other
Robert Chancia at Idaho University, USA, and colleagues predict that Uranus's two moons, Cressida and Desdemona, will collide in the future.Why is there a tidal up and down phenomenon?
Seawater is retained on Earth by gravity, the Moon and the Sun also have gravity for the earth. In particular, the Moon absorbs a mass of water on the ocean surface.