discussion with teacher

Geostationary orbit
- please add a button to reveal & hide "gravitational force" acting on the satellite towards the centre of the Earth for all the modes.

done!

other changes

made to scale
R = 6.37E6 m = 0.637 in model
R geostationary = 4.23E7 m= 4.27 in model

i also added
circular motion r=Re, T = 1.4 hr
circular motion r=2*Re, T = 3.98 hr
circular motion r=3*Re, T =7.30 hr
circular motion r=10.5*Re, T = 48 hr
expanding on the non-geostationary due to speed.

remove simple 3D as EJS4.3.6 supports java 3D and also a bug toggling from simple to java 3d.
enjoy!