hai, now iam uder a deep problem. Be patient! if all the motion is relative, and so all rotation is relative.i am very much convienced with this.but the problem is that ......taking solar system as an example,who is rotating around whom. :rofl: indeed i dont understand why ptolamey's geocentric is abonded. who knows whether sun is rotating around earth? one may say......sun is so massive that it cann't be bounded by earths gravitational field............wait ..wait.....who knows whether gravitational theory is right? indeed my arguement may look stupid.but iam now in this position after a long thought process.see..... if there were a force called BRAVITATION (hee hee haa haa) and which might not be a central force.who knows? ok ok if ur not conveinced with my arguement....leave it.because it is not that easy to say such things. here is different doubt that i have to ask you can you please tell good mathematical method for calculate the trajectories of other planets using geocentric theory..actually i tried it for mercury and venus.its fine. but the problem is arising when i consider some other ones like jupiter. HOW DOES JUPITER'S ORBIT APPEAR TO US.I HAVE SEEN THE TRAJECTORY IFROM PTOLAMEY'S THEORY.BUT I AM NOT ABLE TO DERIVE IT MATHEMATICALLY. CAN ANY BODY HELP ME??