黑洞是一颗恒星坍缩为所知的奇异点。

A black hole is a star that has collapsed into a tiny point known as a singularity.

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The time was in the early 70s, so factory farming was not well-known, was not as dominated as it is today, but it still existed.

那时是70年代早期，工厂化养殖并不为很多人所知,也不如今天这样占主导地位，但当时已经出现了这种方式。

普林斯顿公开课 - 人性课程节选

Roughly speaking, about 1200 B.C., we hear of general attacks that are going on around the Mediterranean against the various civilizations of which we know.

大致说来,大概在公元前一千二百年,爆发了以地中海周围,我们所知的各种文明为攻击对象的,全面战争

耶鲁公开课 - 古希腊历史简介课程节选

So, practitioners who understood what we would know to be chemistry were highly valued in that society. And then, you may expand it to other chemical processes, dyeing of cloth, glassmaking, and metals extraction.

所以，理解我们所知为化学的,先行者们，在那个社会是,非常宝贵的，当时，你可能将其扩展到另一个化学过程，如布料的染色，玻璃的制造，还有金属提取。

麻省理工公开课 - 固态化学导论课程节选