1. Helium is the by product of millennia of radioactive decay from the elements thorium and uranium. 氦是钍和铀元素数千年放射性衰变的副产品。
2. For millennia the average person's stance toward providing for himself had been, ultimately I'm on my own. 几千年来，一般人对于养活自己的立场是，最终我要靠自己。
3. Once the soil has been removed by erosion, only the passage of centuries or millennia will enable new soil to form. 一旦土壤被侵蚀，新的土壤只有经过几个世纪或几千年才能形成。
4. We know that over the past millennia the climate has undergone major changes without any significant human intervention. 我们知道，在过去的几千年里，气候在没有任何大型的人为干预之下发生了剧大变化。
5. While it is unknown just how much of this is true, it is certainly known that silk cultivation has existed in China for several millennia. 虽然我们不知道这其中有多少是真实的，但可以肯定的是，丝绸栽培在中国已经存在了几千年。
