The bouyant force upon an object is equal to the weight of the displaced fluid. Archimedes discovered that sitting in his bathtub. He was so pleased that he ran naked through the streets of Athens yelling, "Eureka!" An excellent way to publicise one's discoveries.
Speaking of displacement, the satellite Pan is seen here orbiting in the Encke Gap of Saturn's Rings. Mark Showalter discovered this moon by analysing wakes and ripples seen in Voyager photographs. Pan orbits within the Rings at only 85% of the Roche Limit, where it was thought that moons could not exist. Pan's influence keeps the Encke Gap open, and Saturn's Rings contain dozens of gaps. There could be many more objects plying through them.
Thank you, Paul and Michael, for additional information on Queen Mary 2. It is hard to describe how big the ship feels. There is that line from GLADIATOR: "I can't believe men can build something so big." The Cunard ships are true ocean liners, designed for long trips at sea. Here both Queen Marys are drawn alongside some buildings from your neighbourhoods. With a length of 1132 feet, QM2 is longer than the Chrysler building is tall. If she were set on the ground in London, her mast would be nearly as tall as St Paul's dome.
TOMORROW: More ships and moons