Science and Sensitivity Science & Computers PHY307/PHY607 Oct. 8, 2002

1. Science and SensitivityScience & ComputersPHY307/PHY607Oct. 8, 2002 Proposals due Thursday, beginning of class. PHY307, Fall 2002

6. 39 SATELLITES, NOW ID’ed

7. Regularities? • Orbital period • Time for satellite to orbit planet or planet or asteroid to orbit Sun. • Rotational period • Time to spin on its axis. PHY307, Fall 2002

8. Rotational period to orbital period Moon • Rotational period to orbital period Phobos • Rotational period to orbital period Deimos • Rotational period to orbital period Thebe • Rotational period to orbital period Io • Rotational period to orbital period Hyperion • Rotational period to orbital period Titania • Rotational period to orbital period Umbriel • Rotational period to orbital period Miranda • Rotational period to orbital period Tethys • Rotational period to orbital period Iapetus • Rotation period of Pluto to orbital period of Charon • Rotation period of Pluto to rotational period of Charon • Orbital period of Mimas to orbital period of Pandora • Orbital period of Mercury to rotational period of Mercury • Orbital period of Pluto to orbital period of Neptune • Orbital period of Cruithne to orbital period of Earth. • Orbital period of Hyperion to orbital period of Titan.

9. Mode locking • Requires friction • so can settle into stable situation • Requires “nonlinearity” • Response to perturbations or outside effects is not just the sum of the responses to individual perturbations or effects. • Kick twice as hard, doesn’t move twice as far. PHY307, Fall 2002

10. Examples • Moon. • Sun. • Walking. • Fireflies interested in reproducing. PHY307, Fall 2002

11. Stability of the Solar System • Some is quite regular. • Looks OK as far as anyone can tell. • BUT • There ARE chaotic elements. • Collisions of asteroids with one planet would be of interest. PHY307, Fall 2002