I'm still waiting for my supper to cook, so I've written a simple solar system simulator. Create any number of 'planets' and put them into random orbits around a star. Sure, some of the planets are going to be ejected into deep space, never to been seen again, but for the lucky few - you may see a stable orbit, and who knows, if the conditions are right maybe life will flourish?
Again, keen students will want to change a few parameters. The solar gravity is a good one to modify, as is the number of planets created. Have fun, and as always, this program will run under the free version of BB4Win, and Windows executables are available on demand.
Source code follows:
REM Solar System Simulator
REM T Street
REM 2014-11-25
MODE 10 : OFF
REM screen dimensions
SCREEN_WIDTH% = 1440
SCREEN_HEIGHT% = 1152
REM -------------------------------------------
REM STUFF TO MUCK AROUND WITH
REM -------------------------------------------
SUN_RADIUS% = 100 : REM pixels
SUN_MASS% = 100 : REM relative units
PLANETS% = 30
REM -------------------------------------------
BLACK% = 1 : COLOUR BLACK%, 0, 0, 0
SUN_COL% = 2 : COLOUR SUN_COL%, 255, 255, 0
PLANET_COL% = 3 : REM colour pot for planets
PLANET_MULT% = 4 : REM size of planet per unit of mass
REM create the planet structure
DIM planet{(PLANETS%-1) x, y, dx, dy, mass, green%, blue% }
REM randomly create planets
PROC_createPlanet( planet{()} )
REM MAIN LOOP
REPEAT
*refresh off
PROC_drawSun
PROC_drawPlanets( planet{()} )
*refresh
WAIT 5
*refresh off
PROC_removePlanets( planet{()} )
*refresh
PROC_move( planet{()} )
PROC_gravity( planet{()} )
UNTIL FALSE
DEFPROC_createPlanet( this{()} )
REM creates random planets
LOCAL i%
FOR i% = 0 TO PLANETS%-1
this{(i%)}.x = RND(SCREEN_WIDTH%)
this{(i%)}.y = RND(SCREEN_HEIGHT%)
this{(i%)}.dx = RND(10)+5
this{(i%)}.dy = RND(10)+5
this{(i%)}.green% = RND(256)-1
this{(i%)}.blue% = RND(256)-1
this{(i%)}.mass = RND(10)
NEXT
ENDPROC
DEFPROC_drawSun
REM draws the yellow star in center of screen
GCOL 0, SUN_COL%
CIRCLE FILLSCREEN_WIDTH% DIV 2, SCREEN_HEIGHT% DIV 2, SUN_RADIUS%
ENDPROC
DEFPROC_drawPlanets( this{()} )
REM draw each planet
LOCAL i%
FOR i% = 0 TO PLANETS% -1
COLOUR PLANET_COL%, 0, this{(i%)}.green%, this{(i%)}.blue%
GCOL 0, PLANET_COL%
CIRCLE FILL this{(i%)}.x, this{(i%)}.y, this{(i%)}.mass * PLANET_MULT%
NEXT
ENDPROC
DEFPROC_removePlanets( this{()} )
REM remove planets from the screen
LOCAL i%
GCOL 0, BLACK%
FOR i% = 0 TO PLANETS% -1
CIRCLE FILL this{(i%)}.x, this{(i%)}.y, this{(i%)}.mass * PLANET_MULT%
NEXT
ENDPROC
DEFPROC_move( this{()} )
REM move planet due to its own velocity
LOCAL i%
FOR i% = 0 TO PLANETS% -1
this{(i%)}.x += this{(i%)}.dx
this{(i%)}.y += this{(i%)}.dy
NEXT
ENDPROC
DEFPROC_gravity( this{()} )
REM apply gravity to each planet from the sun
LOCAL distance
LOCAL i% : REM iterator
FOR i% = 0 TO PLANETS% - 1
distance = SQR( (SCREEN_WIDTH% DIV 2 - this{(i%)}.x)^2 + (SCREEN_HEIGHT% DIV 2 - this{(i%)}.y)^2 )
IF distance<>0 THEN
this{(i%)}.dx += ( this{(i%)}.mass * SUN_MASS% * (SCREEN_WIDTH% DIV 2 - this{(i%)}.x) / distance^2 )
this{(i%)}.dy += ( this{(i%)}.mass * SUN_MASS% * (SCREEN_HEIGHT% DIV 2 - this{(i%)}.y) / distance^2 )
ENDIF
NEXT
ENDPROC
