The orbits of planets in the once popular geocentric Ptolemaic system are epitrochoids.曾经盛行的托勒密地心说体系里的行星轨道就是外旋轮线.Mars and Earth have orbits which change with time...火星与地球的运行轨道随着时间而变化。Other enumeration problems lead us to...
The Earth orbits in an ellipse.地球轨道呈椭圆形。The man - made satellite orbits the earth every 48 hours.那颗人造卫星每48小时绕地球轨道运行一周.They knew each other by sight, but their orbits did not touch.他们见面认识, 但各自的生活圈子互不搭界....