Notes from Independent Study Meeting
                      Jan 27, 2022

Present: Richmond, Dayal

  - Dayal shows results of investigation of timestep

          if timestep too small,
                simulation takes a long time to run
                output file is too large

          if timestep too large,
                energy changes by a lot (more than a few percent)
                Earth leaves its orbit
                simulation is invalid


  - MWR suggests computing these quantities:

                                     current total energy - orig total energy
     fractional change in energy  =  ----------------------------------------
                                                orig total energy


     absolute value of (fractional change in energy)


  - Dayal shows graphs of 
             x pos vs. timestep
             y pos vs. timestep
             y pos vs. x pos      (shows circle of Earth around Sun)

  - goals for next meeting (Mon, Jan 31): 
   
        1)  figure out how to make graph have same scale on X and Y axes
                    so circular orbit looks like a circle

        2)  try running a 200-year simulation of Earth around Sun
                    what is a good range of timesteps?

        3)  create a copy of simulation code
                    replace Earth with "stupid sail"
                    do NOT include any pressure from sunlight
                    run for 2 years
                    what happens to sail?