NAMEplanets - Gravitational simulation of planetary bodies
DESCRIPTIONPlanets is a simple interactive program for playing with simulations of planetary systems. It is great teaching tool for understanding how gravitation works on a planetary level.
The user interface is aimed at being simple enough for a fairly young kid can get some joy of it. There's also a special kid-mode aimed at very young children which grabs the focus and converts key banging into lots of random planets.
- Add Planet
- Place random orbital planet
- Place random planet
- Undo (undoes last planet insertion)
- Reset to empty universe
- Go Back (goes back to just after last planet insertion)
- Click on a planet to delete it
- Toggle bounce (experimental)
- Cursor keys
- c, Space
- Move display to center of mass
- Initiate center of mass tracking
- Zoom in
- Zoom out
- Toggle Pause
- Change all colors randomly
- Toggle Trace
- Double Trace Length
- Halve Trace Length
- Drag a box around a set of planets to follow the center of mass of those planets
- Display help dialog
- Display option dialog
- Toggle kid-mode. Kid mode locks the keyboard and mouse, so the only way to get out is to toggle kid-mode again to get out.
- Load Universe After pressing l, press any other character to load the universe with that name. Universes are stored in ~/.planets/ .
- Save Universe After pressing s, press any other character to save the universe with that name. Universes are saved in ~/.planets/ .
- q, Esc
TECHNICAL DETAILSPlanets uses a fourth-order runge-kutta approximation for the simulation itself. Planet bouncing is achieved by adding a repulsive force to planets at close quarters. Planets is fairly flexible: you can change the gravitational constant, the time-slice of the simulation, and even the exponent used in the gravitational law. Universes are saved in the ~/.planets directory, and are simple human readable and editable files.
BUGSCurrently bouncing doesn't work very well unless you make the time-slice quite small. Ideally, it would be nice to have a billiard-style bounce system, but it's not clear how to do this accurately in the presence of a strong gravitational field.
AUTHORPlanets was written by Yaron M. Minsky <firstname.lastname@example.org> as a gift for his nephew, Eyal Minsky-Fenick.
This manpage was contributed originally by Martin Pitt <email@example.com> for the Debian GNU/Linux system (but may be used by others).