当行星绕太阳运行时，其轨道椭圆的主轴每次都会改变。
The main axis of the planet's orbital ellipse shifts each time when it goes around the sun.
当地球的轨道更接近椭圆时，地球实际上在一年的一部分时间里更接近太阳。
When Earth's orbit is more elliptical, Earth is actually closer to the sun during part of the year.
地球轨道的一个特点是它的离心率，也就是轨道是椭圆而不是圆形的程度。
One characteristic of Earth's orbit is its eccentricity, the degree to which the orbit is an ellipse rather than a circle.
应用推荐