XGrav
X-Grav is a simple physics simulation for a large number of
particles. It simulates the effect of gravity, collisions, heat
dissipation and a simple chemical reaction. The simulation is in no
way meant to be realistic but rather a toy with which you can create
stars, planets and even simple solar systems.
The best way to understand the behaviour of X-grav is by a demonstration. Start by compiling xgrav and then start it by doing:
xgrav -s example1.g
This will start a simulation containing 2000 particles which are all
cold from the begining. After a while these particles will have
collapsed into a few clouds which are warmed up by the friction of
the particles. When the temperature and density of these clouds have
raised enough some of the colliding particles will ignite in a burst
of fusion. This will lead to a chain reaction igniting a large number
of the combustible particles, raising the temperature of the cloud so
rapidly that the particles are blown appart from the increased
pressure. Under most circumstances this sudden reaction will blow out
the initial flames.
However if you wait a while and if the conditions are right you this
will not happen the second or third time the particles form dense
clouds again. The chain reaction will be a little calmer due to less
combustible material and will rather live on. You will now have a
small star which is fueled by continous reactions of colliding
particles.
If you let the simulation run for a while you will see that there are
less and less material left in the stars which can react. As the
stars are cooling down you can note
that they are shrinking until they are cold and dark dwarfs.
As the first clouds of interstellar dust is forming the friction is
slowly building up the heat.
During the simulation you can use the 'a' and 's' keys to zoom in
and out of the center
of the simulation. When you are satisfied with the demonstration you
can use the
escape key to quit the program.
Hopefully this small demonstration will have made you interested in
the simulation.
When we ran this simulation we only used 2000 interacting particles
in order to get
the results somewhat in real time. If you are a little more patient
you can instead run xgrav with the 'record' and the 'play'
settings. By doing 'xgrav -r foo.dat < example2.g' you instruct xgrav
to save all the simulated particles continously in the datafile
'foo.dat'. After quiting xgrav you can later playback and resume the
simulation with 'xgrav -p foo.dat'.
Last modified 03/13/12
As the first clouds of interstellar dust is forming the friction is
slowly building up the heat.
When the heat is high enough, the first chain reactions can
start. Finally leading to the creation of a stable star.