Tony

Gravity Simulator continuously shifts the entire system so that the first object in the simulation always sits at (0,0,0). If it drifts to (1,1,1) then all objects are shifted (1,1,1). This prevents the solar system from drifting light years away from the origin. Since it uses double precision variables, positions in the solar system can be specified to exact centimeters. But once it drifts far from the origin, it is only meteraccurate, then kmaccurate, then AUaccurate... etc... This causes some strange errors, such as square orbits. That is why Gravity Simulator continuously recenters. So when you output data, the Sun should always have a position of (0,0,0). So you'll have to compute the barycenter yourself in your spreadsheet.
