from vpython import * scene.caption = """To rotate "camera", drag with right button orCtrl-drag. To zoom, drag with middle button or Alt/Option depressed, or use scroll wheel. On a two-button mouse, middle is left + right. To pan left/right and up/down, Shift-drag. Touch screen: pinch/extend to zoom, swipe or two-finger rotate.""" scene.forward = vector(0,-.3,-1) G = 6.7e-11 # Newton gravitational constant giant = sphere(pos=vector(-1e11,0,0), radius=2e10, color=color.red, make_trail=True, trail_type='points', interval=10, retain=50) giant.mass = 2e30 giant.p = vector(0, 0, -1e4) * giant.mass dwarf = sphere(pos=vector(1.5e11,0,0), radius=1e10, color=color.yellow, make_trail=True, interval=10, retain=50) dwarf.mass = 1e30 dwarf.p = -giant.p dt = 1e5 while True: rate(200) r = dwarf.pos - giant.pos F = G * giant.mass * dwarf.mass * r.hat / mag(r)**2 giant.p = giant.p + F*dt dwarf.p = dwarf.p - F*dt giant.pos = giant.pos + (giant.p/giant.mass) * dt dwarf.pos = dwarf.pos + (dwarf.p/dwarf.mass) * dt