Provided by: planets_0.1.13-19_amd64
planets - Gravitational simulation of planetary bodies
Planets 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.
Universe definition a Add Planet j Place random orbital planet r Place random planet u Undo (undoes last planet insertion) e Reset to empty universe g Go Back (goes back to just after last planet insertion) Mouse Click on a planet to delete it Physics b Toggle bounce (experimental) Display control Cursor keys Panning c, Space Move display to center of mass x Initiate center of mass tracking = Zoom in - Zoom out p Toggle Pause o Change all colors randomly t Toggle Trace d Double Trace Length h Halve Trace Length Mouse Drag a box around a set of planets to follow the center of mass of those planets Program control H Display help dialog k Display option dialog Ctrl-Shift-k 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. l Load Universe After pressing l, press any other character to load the universe with that name. Universes are stored in ~/.planets/ . s Save Universe After pressing s, press any other character to save the universe with that name. Universes are saved in ~/.planets/ . q, Esc Quit
Planets 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.
Currently 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.
Planets was written by Yaron M. Minsky <email@example.com> as a gift for his nephew, Eyal Minsky-Fenick. This manpage was contributed originally by Martin Pitt <firstname.lastname@example.org> for the Debian GNU/Linux system (but may be used by others). April 20, 2003 planets(1)