smoove

Hello, I have a different question than tonyza2006, but concerning Newton's law of gravitation, I hope I was right to post it here then. I am trying to create a program simulating the solar system's behaviour, using Newton's first and second law: F = G m1 m2 / r squared F = m a I understand that these two equations are precise enough approximations to explain and calculate our actual observation of the solar system's behaviour. Note that I already managed to create a stable system containing the Sun, Mercure, Earth and Jupiter. Now let us assume that we have the following static situation: (SUN) -------------------- (MOON) ---- (EARTH) If I apply "a = F / m" with the correct values (with the help of Wikipedia), I obtain the following results (you are welcome to re-calculate them to check): Sun radius: 695 * 10^6 meters Earth radius: 6 * 10^6 meters Moon radius: 1.7 * 10^6 meters Distance Earth to sun: 150 * 10^9 meters Distance Moon to earth: 400 * 10^6 meters Sun mass: 2 * 10^30 kg Earth mass: 6 * 10^24 kg Moon mass: 7.34 * 10^22 kg Acceleration from the earth to the sun : 0.0058776287291389753714553965137712 Acceleration from the moon to the earth: 0.0024092077399680867365033264189728 Acceleration from the moon to the sun : 0.00596459693833060296825931239269 Meaning that the Moon is more attracted by the Sun than the Earth actually is (I am not even sure it is logical...); but more important, that the Moon is two times more attracted by the Sun than by the Earth. My program then basically makes the Moon rotate around the Sun without maintaining an orbit around the Earth. What am I missing to find the appropriate balance of that system? Remark: we first assumed that the system was static, but the problem is even worse if we imagine that the Moon actually managed to rotate once around the Earth. It will then have a none null speed and will eventually be directed straight to the Sun, making it even more difficult for the Earth to maintain its satelit's orbit. --------| | (SUN) --------------------- (EARTH) | (MOON) | <--------| Thank you for your listening, Sorry about the last scheme: it was supposed to show the Moon starting to rotate from one side of the Earth, then finally poping out on the other side.