.TH planets 1 "April 20, 2003"
planets \- Gravitational simulation of planetary bodies
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
.SS Universe definition
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)
.SS Display control
Move display to center of mass
Initiate center of mass tracking
Change all colors randomly
Double Trace Length
Halve Trace Length
Drag a box around a set of planets to follow the center of mass of
.SS Program control
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.
After pressing l, press any other character to load the universe with
that name. Universes are stored in ~/.planets/ .
After pressing s, press any other character to save the universe with
that name. Universes are saved in ~/.planets/ .
.SH TECHNICAL DETAILS
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.
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.
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).