And that's really neat to think about, because photons, of course, are massless particles, they have no mass, so it's neat to think about something that has no mass, but that actually does have a momentum.

而且那真的不容易想明白，因为光子，当然是无质量的粒子，它们没有质量，所以这个真的不容易想明白,一些物体没有质量，但是它们事实上确实有动量。

麻省理工公开课 - 化学原理课程节选

Yes. A sperm. Did everyone get that? No. Okay.

对了　一个精子　大家都明白了吗　没有　好吧。

耶鲁公开课 - 1945年后的美国小说课程节选

they're not engaged in P-functioning. That's pretty clear.

他们没有人格功能性，这点很明白。

耶鲁公开课 - 死亡课程节选

So, for these reasons and probably for hundred more that I haven't thought of, we can understand why these people go against the natural instinct of staying put and go adventuring out, seeking a new home someplace in the Mediterranean.

那么综上所述,当然还有很多因素我们没有涉及到,我们能够明白为什么这些人,不顾人类本性,执意远征,在地中海寻找新的家园

耶鲁公开课 - 古希腊历史简介课程节选