The Earth's axisof rotation is tilted in relation to the ecliptic plane, an imaginary surface through Earth's orbit around the sun.
地球的自转轴与黄道面呈一定角度。黄道面是地球公转轨道所在的一个假想平面。
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The angular difference between the astronomical axis and the axisof figure called a "nutation" causes an earth orbit al spirical oscillation known as the famous chandler "wobble".