The reason lies in its gravity.
其原因在于月球的重力。
新概念英語第四冊
Lesson 35 Space odyssey
?? 句中詞匯解析
從本句中提取的重要詞匯
n. 重力;萬有引力，地心引力;重要性，嚴重性;嚴肅，莊重;
?? grav重+ity名詞后綴 → 莊重；地心吸力
"Newton's law of gravity"
牛頓萬有引力定律
近義：ponderosity, seriousness, circumspection, gravitation, importance, severity
反義：skittishness, superficiality, trifling, triviality, lightness, flippancy
n. 理由;原因;理性;理智;
vt.& vi. 推理，思考;爭辯;辯論;向…解釋;
?? 再（re）生一個（a）兒子(son)， 理由是第一個兒子夭折了
"The reason for the flood was that heavy rain."
水災是那場大雨造成的.
近義：ratiocinate, think, conclude, deduce, deduct, motivation
反義：idiocy, applesauce, imbecility, inaccuracy, inanity, mistake