“天底”的拼音为：tiān dǐ...

感觉上我们好像已从天底走到了天顶.It felt as if we had traveled from nadir to zenith.天底天球上,在观测者垂直向下的一点, 与天顶完全相对.A point on the celestial sphere directly below the observer, diametrically opposite the zenith....

“天底”的英语可以翻译为：nadir ...