dinky simulation of earth sun system, storing here

earthsun.js

#!/usr/local/bin/node

var simulateEarthSunSystem = function(){
	var G = 6.67e-11;

	var earth = {
		x: 150e9, // m
		y: 0,
		radius: 6371e3, // m
		m: 5.9e24, // kg
		vx : 0, // m/s
		vy : 30e3 // m/s
	};

	var sun = {
		x: 0,
		y: 0,
		radius: 696e6, // m
		m: 2.0e30, // kg
		vx: 0, // m/s
		vy: 0 // m/s
	};

	var gravity = function(obj1, obj2){
		dx = obj2.x - obj1.x;
		dy = obj2.y - obj1.y;

		var r = Math.sqrt(Math.pow(dx, 2) + Math.pow(dy, 2));
		var fMag = G * obj1.m * obj2.m / (r*r);
		var fx = fMag * dx / r;
		var fy = fMag * dy / r;
		return {
			fx: fx,
			fy: fy
		};
	}

	var log = function(d){console.log(d);}

	var objects = [earth, sun];
	var dt = 86400; // s
	var t = 0; var maxT = 32000000; // s

	var data = {}; // maps time in seconds to the positions and speeds of the sun and the earth 

	var updateData = function(t, earth, sun){
		data[t] = {
			earth: {
				x: earth.x, // m
				y: earth.y,
				radius: earth.radius, // m
				m: earth.m,
				vx : earth.vx,
				vy : earth.vy
			},
			sun: {
				x: sun.x,
				y: sun.y,
				radius: sun.radius,
				m: sun.m,
				vx: sun.vx,
				vy: sun.vy
			}
		};	
	}

	for(var t = 0; t < maxT; t += dt){
		updateData(t, earth, sun);
		for(var i = 0; i < objects.length; i++){
			var force = gravity(earth, sun);
			var ax = force.fx / objects[i].m;
			var ay = force.fy / objects[i].m; // (m/s)/s
			
			// integrate the changes in speed
			var dvx = ax * dt;
			var dvy = ay * dt;
			objects[i].vx += dvx;
			objects[i].vy += dvy;

			// integrate the changes in position
			var dx = objects[i].vx * dt;
			var dy = objects[i].vy * dt;
			objects[i].x += dx;
			objects[i].y += dy;
		}
		
		if(t+dt >= maxT){
			updateData(t, earth, sun);
		}
	}

	return data;
}


data = simulateEarthSunSystem();
console.log(data);