Studying
the process of planetary system evolution is not an easy task. Trying
to
figure out how just 3 mutually interacting objects will behave is more
than
paper and pencil methods can handle. Some of the greatest minds in
science
tried heroically but could make only limited progress with the
so-called
3-body problem because of the complexity of the motions. To really see
what
can happen when lots of planets interact you need a computer and that
is
what this Interactive is all about. The tool you are playing with here
would
have been considered state of the art science just decades ago when
computers
first became research tools.
Here
are the steps you need to follow to get started:
Notice the text on the screen that gives you information about size,
time
and mass "scales" used in the simulations. Notice on the lower left
hand
side there are labels that show the current position of the cursor on
the
screen.
1.
Press "presets". You will get a menu of possible systems to begin
with. You may start
with just the Sun, the Sun and Earth, the entire solar system out to
Saturn or
a random distribution of planets. There are 2000 random distributions
to choose from.
To change your random distribution change the number in the box labeled
"System #" and
hit Enter on your keyboard. Click the "Crowded" button to make random
systems with the planets packed together. These tend to get more
interesting behavior early on in their
evolution.
You can add a new planet to any of these preset systems. Just choose
the new planet's
mass by moving the MASS slider-bar. You can go all the way from
Mercury sized masses up
to "Hot Jupiter" mass bodies.
2.
Use the mouse to locate the position where you want to place the
planet.
Left-click on the mouse and a circle appears whose size is proportional
to the planet's mass. This planet will begin on a circular orbit. You
can
have up to 20 planets in a system at once. You can also
choose a planet's initial speed and direction by right-dragging on the
mouse
and "pulling" the velocity arrow outward from the planet.
****
Note: Preset planets always begin on circular orbits ****
3.
Press "Play" to begin watching the system evolve. Use the speed
slider-bar
to speed-up or slow-down the evolution (this is good for when you want
to
recreate a system and watch it evolve more slowly).
4.
You can hit "Pause" to stop the evolution at any time. You can add
planets
while the evolution is running or paused.