首先，他们必须搞清楚火星上是否曾经存在过生命。

To begin with, they will have to find out whether life has ever existed on the planet of Mars in the past.

youdao

由于自然选择，大多数曾经存在过的物种已经灭绝，所以这不是一个新现象。

Thanks to natural selection, most species that have ever lived has already gone extinct, so this is not a new phenomenon.

youdao

木星、土星、天王星和海王星。这些都是气体行星，是太阳系的四个重量级。但曾经存在第五个行星吗？

Jupiter, Saturn, Uranus, and Neptune. Those are the gas giants, the four heavyweights of the solar system. But was there once a fifth?

youdao

First, that everybody knows realities, people believe that because we all immersed in it, and that already defeats models that you might have.

第一条便是，每个人都知道现实，人们相信现实，因为我们都存在于现实中，现实可能摧毁了你曾经有过的世界观。

麻省理工公开课 - 电影哲学课程节选

Now, neurons are connected and they talk to one another and it used to be thought they were tied to one another like a computer, like you take wires and you connect wires to each other, you wrap them around and connect them.

神经元之间是相互联系的,它们彼此间存在信息的传递,人们曾经以为它们是被绑在一起的,就像计算机,就像是你要把所有的电线接在一起一样,你把电线缠起来,连在一起

耶鲁公开课 - 心理学导论课程节选