# Aaron Titus
# High Point University
# Matter & Interactions, Problem 2.2
# Binary Stars

from visual import *
from __future__ import division

scene.range=7e11
scene.autoscale=0
scene.width=800
scene.height=800

s1=sphere(radius=7e9, color=color.yellow, pos=vector(1.5e11,0,0))
s2=sphere(radius=7e9, color=color.red, pos=vector(-1.5e11,0,0))

s1.m=2.0e30
s2.m=10.0e30

s1.p=s1.m*vector(0,5e4,0)
s2.p=-s1.p

G=6.7e-11

t=0
dt=1.0e5

trail1=curve(color=s1.color)
trail2=curve(color=s2.color)

s1.Fnet=vector(0,0,0)
s2.Fnet=vector(0,0,0)


Fscale=2e10/1e27
s1.FnetVector=arrow(pos=s1.pos, axis=s1.Fnet*Fscale, color=color.blue)
s2.FnetVector=arrow(pos=s2.pos, axis=s2.Fnet*Fscale, color=color.blue)

pScale=2e11/s1.p.mag
s1.pVector=arrow(pos=s1.pos, axis=s1.p*pScale, color=color.cyan)
s2.pVector=arrow(pos=s2.pos, axis=s2.p*pScale, color=color.cyan)


while 1:
	rate(100)
	
	rvec=s1.pos-s2.pos #vector from s2 to s1
	rmag=mag(rvec) #magnitude of r
	rdir=rvec/rmag #unit vector from s2 to s1
	
	Fgrav=G*s1.m*s2.m/rmag**2.0
#	Fgrav=0
	
	s2.Fnet=Fgrav*rdir
	s1.Fnet=-s2.Fnet
	
	s2.p=s2.p+s2.Fnet*dt
	s2.pos=s2.pos+s2.p/s2.m*dt
	
	s1.p=s1.p+s1.Fnet*dt
	s1.pos=s1.pos+s1.p/s1.m*dt
	
	trail1.append(pos=s1.pos)
	trail2.append(pos=s2.pos)
	
	s1.pVector.pos=s1.pos
	s1.pVector.axis=s1.p*pScale
	s2.pVector.pos=s2.pos
	s2.pVector.axis=s2.p*pScale
	
	s1.FnetVector.pos=s1.pos
	s1.FnetVector.axis=s1.Fnet*Fscale
	s2.FnetVector.pos=s2.pos
	s2.FnetVector.axis=s2.Fnet*Fscale
	
	t=t+dt
	
#	print Fgrav