We don't understand quantum physics enough to know if these closed timelike curves could or couldn't exist.

我们对量子物理学的了解还不够，不知道这些封闭的曲线是否存在。

Without getting into too much detail, a time machine like a Tipler cylinder could create a closed timelike curve.

简单来，像提普勒柱体这样的机器可出一个封闭的曲线。

In a closed timelike curve, when you travel to the past, you've always been a part of that past.

在一个封闭的曲线中，当你回到过去，你就一直是过去的一部分。

They also have regions inside them where it  would be possible to travel to your own past along closed timelike curves which creates one  of those time-travel grandfather paradoxes.

它们内部还存在一些区域，人们可沿着封闭的类曲线回到自己的过去，这就产生了旅行祖父悖论之一。