Sir Isaac Newton would be amazed by this awesome video, showing Saturn moons causing gravitational waves as they orbit near its F Ring. These images can only be taken every 15 years, during Saturn's equinox. Thankfully, Cassini is there now.
In the video you can see Prometheus (in the inner side) and Pandora (on the outer side), disturbing and smoothing the rings one after the other, which is why they are called shepherd moons. Things get even more spectacular in the Keeler gap, inside the A ring. There, Daphnis surfs the ring creating beautiful twirls.
These photos are very rare. You can only take them during the equinox, when the sunlight hits its rings at an angle that makes them look their best. That was one of the reasons that made NASA's Jet Propulsion Laboratory seek more funding to extend the mission. Here's where Cassini is today.
The Cassini Equinox Mission mission is going to last until September 2010. Hopefully, NASA will be able to secure more funds for the next mission extension, which will take Cassini closer and closer to the rings, crashing against Saturn on 2017. The technical term to describe that mission is: Fraking kick arse.