Standard model: Earth & Mars accelerations and retrograde, and question

Units: velocity was in AU / Day so acceleration is AU / Day^2

Question from laymen: why Mars acceleration isn’t symmetric?

Simple notebook to play around using Astropy library: colab notebook

Now fun.

I’ve run naive ~“Newtonian simulator” given initial standard system weights/position/velocities and recorded differences in position between positions in simulator and positions on simple ephemerides (orbit models delivered by agencies).

Simulation time: since yesterday till year 2350
X axis: sample number
Y axis: difference in positions, in AU units

What can be seen that there is a Sun’s drift not accounted for by agencies (stationary Sun religion? :wink: ).

If we subtract this drift from all objects it gives:

Now we see that Sun-Earth is described by Newtonian ephemerides (little drift from simulator) and rest of the system experience some additional motion (rotation, tilt?).

And that the Mercury is it its own category.

Sharing because I’ve found it quite funny.