20 quadrillion sounds like a lot of ants, and it is. To give you an idea, that's two and a half million ants for every human on Earth. 

20千万亿听起来像是很多只蚂蚁，事实也确实如此。这就相当于地球上每一个人对应250万只蚂蚁。 

To count them at one a second would take 634 million years. So, no one's tried that. 

以每秒数一只蚂蚁的速度，要6.34亿年才能数完。所以，没有人尝试过。

But the scientists involved in this report have made their estimate by consulting hundreds of studies from different habitats around the world. 

然而参与这项研究的科学家们通过查阅世界各地不同蚂蚁栖息地的数百项研究做出了估算。 

The study warns that the staggering figure may be an underestimate because of the lack of data from regions including Central Africa and Asia. 

该研究提醒，由于缺少包括中非和亚洲等地区的数据，所以尽管这个数字惊人，但可能仍低估了蚂蚁的实际数量。

词汇表

quadrillion 一千万亿
give someone an idea 让某人大致了解情况
estimate 估算，估计
consulting 查阅
staggering 惊人的
underestimate 低估