home
***
CD-ROM
|
disk
|
FTP
|
other
***
search
/
AMOS PD CD
/
amospdcd.iso
/
sourcecode
/
various
/
galaxies.doc
< prev
next >
Wrap
Text File
|
1990-04-07
|
3KB
|
84 lines
Colliding Galaxies Simulation Amiga Version 1.0
Original program in BBC Basic by Andrew Rankin 1989
Amiga Version translated into AMOS Basic by Jeff Tullin 1991
If you are reading this Andrew - where are you now?
Overview (Hugely simplified for thickies like me!!)
The shape and form of most galaxies can be divided into 3 main
categories:
Elliptical - which have no evident internal structure.
Spiral - a central core surrounded by a thin disc of trailing
arms - like our own,
Irregular - those which do not fit into either of these groups.
There has been much conjecture about how these forms of galaxy
have arisen, and whether one form, through interaction with an
external mass, can change into another.
Now, Andrew's original article about the laws of physics, gravity
galactic structural change, and black holes is a very good read
if you are interested, and I recommend that you dig out a back
edition of Acorn User (July 1989) to examine it in more detail.
BUT, the fact is, most people just want to see what the program
does!
So-
INSTRUCTIONS:
The computer will simulate the collision of two galaxies, using a
very simplified map of their starfields, and a much simplified
view of Newtonian physics as an algorithm.
The mass of each galaxy is assumed to exist as a point at the
centre of the cluster.
The whole star field is represented by a number of rings of
stars.
You will be asked to enter how many rings of stars you wish to
use. Try a low number like 3 for your first attempts, as the time
factor for each calculation increases alarmingly for every added
star. The same logic applies to the next question, regarding how
many stars each ring contains. Try 10 or so until you know you
have an interesting pattern.
The next parameter is the mass of the intruder galaxy, as a % of
the target. So, 100 entered here would mean both galaxies had the
same mass. 10 would mean that the intruder was 1/10 of the mass.
The position of the intruder is entered in Cartesian form, and
is relative to the centre of the target galaxy.
So: X =20 Y=-10 Z=10 puts the intruder North, West, and above.
The velocity in each plane is expressed in the same terms.
Note, if the starting X position is , say, 20, then you will need
to use a negative velocity like -0.02 to ensure that the intruder
actually did some intruding. A positive value would have meant it
span off further away into space!
Some sample data for you to try:
MASS % Position Velocity
X Y Z X Y Z
100 7.5 0 35 0 0 -1
25 40 10 10 -1 0 0
25 -30 30 0 0 -0.34 -0.34
100 0 30 10 0 0 -0.35
While the program is running, it is possible to halt the flow
by pressing a key.
You get 3 options - continue from where you halted,
restart,
or save the screen as an IFF file, for later
manipulation/printing.
Th-th-th-thats all folks!
The original program was based on an article by
MC Schroeder and NF Cumins in the December 1988 ASTRONOMY mag.
Have fun.