public CelestialObject clone() {
try {
CelestialObject obj = (CelestialObject) super.clone();
obj.position = new PVector(obj.position.x, obj.position.y);
obj.velocity = new PVector(obj.velocity.x, obj.velocity.y);
obj.acceleration = new PVector(obj.acceleration.x, obj.acceleration.y);
obj.alForces = cloneArrayList(obj.alForces);
return obj;
} catch (final CloneNotSupportedException ex) {
throw new AssertionError();
}
}