theory of expounding appearance in the night sky

例句：

1. 1.The professor expounded the principles of calculus in his lecture.
   教授在他的讲座中阐述了微积分的原理。
2. 2.The scientist expounded on the importance of environmental conservation.
   科学家阐述了环境保护的重要性。
3. 3. The book expounds on the history of ancient Egypt.
   这本书详细讲述了古埃及的历史。