Lǎoshī jiǎng dìqiú zìzhuàn, yǐnyòng le "zuò dì rì xíng bā wàn lǐ".
Explaining Earth's rotation, the teacher cited 'sitting still, one travels eighty thousand li a day.'
Tips
history
From 《七律二首·送瘟神》 by 毛泽东 (Mao Zedong, 1958), written after reading that schistosomiasis had been eliminated in Yujiang: '坐地日行八万里,巡天遥看一千河。' The 8万里 (40,000 km) is roughly Earth's circumference — 'you ride that distance daily without moving.'
usage
里 here is the Chinese li (~500m), so 八万里 ≈ 40,000 km — the poetic approximation of Earth's equator.