ORBIT.BAS 28 September 1997 by Marc Kummel aka Treebeard. Contact mkummel@rain.org, http://www.rain.org/~mkummel/ About ORBIT: -------------- Parable.-- Those thinkers in whom all stars move in cyclic orbits are not the most profound: whoever looks into himself as into vast space and carries galaxies in himself also knows how irregular all galaxies are; they lead into the chaos and labyrinth of existence. F. Nietzsche, The Gay Science ORBIT is an update of an old Hercules program from the Vault (1989) that demonstrates star cluster dynamics with a simple n-body gravity simulator. I rewrote this using NPF frame routines as an assignment for the Astronomy Acadamy at Dunn High School in 1995. It works, but the editor could use work. I hope to revise this someday. ORBIT shows how complex dynamics arise from simple interactions that are iterated over time. I find it fascinating how so much of modern Chaos and Complex Dynamics theory come right from the classic Newtonian models of pendulums and solar system dynamics. The long term stability of the solar system is *still* an open question! All units in this program are relative with no obvious physical meaning. The simulation slows down to deal with close encounters to avoid an exagerated slingshot effect, but this tack fails for *very* close encounters. A few lessons I've learned playing with this simulation: * Why binary and ternary stars are so common * How the "slingshot effect" breaks up stellar nurseries * Why collisions are so rare * Why it's hard to acheive orbits with long term stability * The butterfly effect: small differences in initial conditions make BIG differences later on Upzip the archive into a directory and type "ORBIT" to begin. Press to begin an animation. Press ile uit to exit the program. There are editing options in the menus so you can create and save/load your own clusters as TBO files. It's hard to achieve stable orbits! File List: ------------ The files below the dotted line are source files that can be deleted if you don't need then, but I won't do it for you. ORBIT.EXE DOS executable ORBIT.ICO an icon for Win31 VGAOEM.FON Win31 font in case it's not on your system *.TBO saved orbit data README.TXT this file TBVAULT.TXT about Treebeard's Basic Vault ------------ ORBIT08.MAK file list for PDS/QB ORBIT08.BAS source code: main module XQB.BAT batch file to start PDS with source code MAKE.BAT batch file to compile and link from DOS prompt ORBIT was written for MS Basic PDS 7.10. QB4.5 will probably need some changes. It won't work with QBasic. To use the source code, you will also need the following files from my NPF program archive, also available from Treebeard's Basic Vault at http://www.rain.org/~mkummel/basic. Copy the files to your CURVES directory. The code requires special library routines and EMS sharing, so start PDS with /L TBLIB and /ES options, or use the XQB.BAT batch file. The required files are: NPSUP.BI include file of global declarations and variables GFONT5.BAS code module to use Windows *.FON fonts EMS4.BAS code module to use expanded memory SBSUP16.BAS code module of support routines TBLIB.QLB Quick Library of misc assembler routines TBLIB.LIB Library files for compiling Sources: ---------- A.K. Dewdney, "A Cosmic Ballet" in _The Armchair Universe_, Freeman, 1988. Originally a Computer Recreations column in Scientific American. Explains the algorithms I use. (And the shortcomings.) Richard Feynman, _Lectures On Physics_ v.1, Adison-Wesley, 1963. Sec. 9-7. Classic account steps through the math of a solar system simulation. (Also available on audio CD?) Ivars Peterson, _Newton's Clock: Chaos in the Solar System_, Freeman, 1993. Recent book with general history. Conditions: ------------- This program and source code are yours to use and modify as you will, but they are offered as freeware with no warranty whatsoever. Give me credit, but do not distribute any changes under my name, or attribute such changes to me in any way. You're on your own! Send comments and fixes to: Marc Kummel aka Treebeard mkummel@rain.org http://www.rain.org/~mkummel/ For more interesting Basic software with source code, check out Treebeard's Basic Vault at http://www.rain.org/~mkummel/basic/