I have a very quick question, and I figured because this is an algorithmic question, perhaps someone would be able to answer this for me here.

I've done a small algorithm in c++ to calculate the coordinates of planets based on the force applied to them, which gives the acceleration, velocity, and finally position (all in components)

I'll explain my issue first and attach my code at the bottom.

I'm not sure if this is an issue or not, but the sun is moving (in meters) quite far away from the origin. I'm aware that the sun is supposed to move a small distance due to the pull of the larger planets, but the coordinates are reaching into the tens of thousands of meters - which does not seem to be logical to me.

The processing for my algorithm is as follows:

-Reset force to 0;

-Get the sum of all forces by F += GM(x[j]-x[i])/r^3

-calculate specific planet's acceleration by the equation a = F/m

-calculate specific planet's velocity by V = Vinitial + a*t

-calculate specific planet's position by X = Xinitial + v*t

-loop

To me, this sounds like this should make sense - and so I figured it was an algorithmic error.

Anyone who's good in physics or algorithm have any idea?

Below is the actual C++ code:

where objects is a struct:Code:double Fx[10], Fy[10], Fz[10]; // Array of force vectors float gravity_constant = 8.99E-9; // Kepler's gravity constant // Set the forces of all the planets to 0 for( int i = 0; i < 10 ; i++) { Fx[i] = 0; Fy[i] = 0; Fz[i] = 0; } for( int i = 0; i < 10 ; i++) { for( int j = 0; i < 10 ; i++) { if(j!=i) // if not itself (added to ensure no division by zero error) { // calculate the force at x Fx[i] += (objects[j].x - objects[i].x) / sqrt( pow((objects[j].x - objects[i].x),2) + pow((objects[j].y - objects[i].y),2) + pow((objects[j].z - objects[i].z),2)) * (gravity_constant * objects[i].mass * objects[j].mass) / ( pow((objects[j].x - objects[i].x),2) + pow((objects[j].y - objects[i].y),2) + pow((objects[j].z - objects[i].z),2)); // calculate the force at y Fy[i] += (objects[j].y - objects[i].y) / sqrt( pow((objects[j].x - objects[i].x),2) + pow((objects[j].y - objects[i].y),2) + pow((objects[j].z - objects[i].z),2)) * (gravity_constant * objects[i].mass * objects[j].mass) / ( pow((objects[j].x - objects[i].x),2) + pow((objects[j].y - objects[i].y),2) + pow((objects[j].z - objects[i].z),2)); // calculate the force at z Fz[i] += (objects[j].z - objects[i].z) / sqrt( pow((objects[j].x - objects[i].x),2) + pow((objects[j].y - objects[i].y),2) + pow((objects[j].z - objects[i].z),2)) * (gravity_constant * objects[i].mass * objects[j].mass) / ( pow((objects[j].x - objects[i].x),2) + pow((objects[j].y - objects[i].y),2) + pow((objects[j].z - objects[i].z),2)); } } } time += interval; // Increase time by the interval // Loop for calculating acceleration, velocity, and position for( int i = 0; i < 10 ; i++) { // calculate acceleration objects[i].ddx = Fx[i] / objects[i].mass; objects[i].ddy = Fy[i] / objects[i].mass; objects[i].ddz = Fz[i] / objects[i].mass; // calculate velocity objects[i].dx += objects[i].ddx * interval; objects[i].dy += objects[i].ddy * interval; objects[i].dz += objects[i].ddz * interval; // calculate position objects[i].x += objects[i].dx * interval; objects[i].y += objects[i].dy * interval; objects[i].z += objects[i].dz * interval; // Output the objects drawPlanet(i, objects[i].x, objects[i].y, objects[i].z); }

and initialized with starting positions/valuesCode:struct tagObjects { double x, dx, ddx; // x component of position, velocity, acceleration double y, dy, ddy; // y component of position, velocity, acceleration double z, dz, ddz; // z componont of position, velocity, acceleration double mass; // mass of the object (planet) double radius; // radius of the object (for deciding width of spheres) }objects[11];

Code:objects[0].mass = 1.99E+30; objects[0].radius = 109; objects[0].texture = NULL; objects[0].x = objects[0].y = objects[0].z = 0; objects[0].dx = 9.303626; objects[0].dy =-11.739118; objects[0].dz =-5.243946; // mercury objects[1].mass = 3.34E+23; objects[1].radius = 0.382512033; objects[1].texture = NULL; objects[1].x =-20665696392; objects[1].y =-59636889090; objects[1].z =-29712844059; objects[1].dx = 3.66E+04; objects[1].dy =-9.51E+03; objects[1].dz =-8.88E+03; // venus objects[2].mass = 4.87E+24; objects[2].radius = 0.948840564; objects[2].texture = NULL; objects[2].x =-1.07478E+11; objects[2].y =-6401037913; objects[2].z = 3920831085; objects[2].dx = 8.82E+02; objects[2].dy =-3.19E+04; objects[2].dz =-1.45E+04; // earth objects[3].mass = 5.98E+24; objects[3].radius = 1; objects[3].texture = NULL; objects[3].x =-26516914541; objects[3].y = 1.32754E+11; objects[3].z = 57555479554; objects[3].dx =-2.98E+04; objects[3].dy =-4.78E+03; objects[3].dz =-2.06E+03; // mars objects[4].mass = 6.40e23; objects[4].radius = 0.532603753; objects[4].texture = NULL; objects[4].x = 2.08092E+11; objects[4].y = 1150108018; objects[4].z =-5098849339; objects[4].dx = 1.30E+03; objects[4].dy = 2.39E+04; objects[4].dz = 1.09E+04; // jupiter objects[5].mass = 1.90E+27; objects[5].radius = 11.2089807; objects[5].texture = NULL; objects[5].x = 5.94749E+11; objects[5].y = 4.1426E+11; objects[5].z = 1.63068E+11; objects[5].dx =-7.89E+03; objects[5].dy = 1.02E+04; objects[5].dz = 4.54E+03; // saturn objects[6].mass = 5.69E+26; objects[6].radius = 9.44920901; objects[6].texture = NULL; objects[6].x = 9.48999E+11; objects[6].y = 9.31359E+11; objects[6].z = 3.4387E+11; objects[6].dx =-7.44E+03; objects[6].dy = 6.12E+03; objects[6].dz = 2.85E+03; // uranus objects[7].mass = 8.67E+25; objects[7].radius = 4.00730625; objects[7].texture = NULL; objects[7].x = 2.17596E+12; objects[7].y =-1.85516E+12; objects[7].z =-8.43327E+11; objects[7].dx = 4.66E+03; objects[7].dy = 4.29E+03; objects[7].dz = 1.81E+03; // neptune objects[8].mass = 1.03E+26; objects[8].radius = 3.88266098; objects[8].texture = NULL; objects[8].x = 2.5472E+12; objects[8].y =-3.41681E+12; objects[8].z =-1.46188E+12; objects[8].dx = 4.50E+03; objects[8].dy = 2.91E+03; objects[8].dz = 1.08E+03; // pluto objects[9].mass = 1.03E+26; objects[9].radius = 0.185008075; objects[9].texture = NULL; objects[9].x =-1.42071E+12; objects[9].y =-4.20637E+12; objects[9].z =-8.84208E+11; objects[9].dx = 5.28E+03; objects[9].dy =-1.96E+03; objects[9].dz =-2.19E+03;

Please, if anyone has any ideas of what I'm doing wrong - assuming these values are wrong as I think they are - please send reply and tell me what I am doing wrong