He f ring of saturn, located just outside the a ring, is caused by two small one just inside and one just outside the f ring, that shepherd orbiting material into a narrow ring.

The F Ring is caused by two small Moons, that shepherd orbiting material into a narrow ring. NASA's Cassini mission helped to reveal hot Saturn's rings were formed, how the ring maintain their orbit and what these rings were at first (comets,asteroids or moons). Saturn's rings are the largest and the most spectacular.

It is the doctrine that the us had the right and duty to expand throughout north america. it just means they believed they had the right to expand westward and they did! they stated with the 13 colonies and then they kept moving gaining different territories throughout the years