GlowScript 2.7 VPython

sphere(pos=vector(0,0,0),radius=1,color=color.yellow)
planet=sphere(pos=vector(10,0,0), radius=0.2,color=color.green, make_trail=True)
#scene.camera.follow(planet)
planet.v=vector(0,2.5,0)
m=1; G=1
M=100
dt=0.005

while True:
    rate(400)
    r=planet.pos
    F=-G*M*m*r.hat/(mag2(r))
    a=F/m
    planet.v=planet.v + a*dt
    planet.pos=planet.pos + planet.v*dt