Lesson 17
第17课
Television Day:Computers
电视日:计算机
"...the astronauts are returning to earth at exactly 5.24."
...宇航员将于5:24整回到地球,
Splash-down will be in the Pacific,427 miles west of Hawaii.
"并将在位于夏威夷西部427英里的太平洋海面上溅落."
You have often heard announcements like this on television.
你常会从电视听到上述的预告.
Scientists can tell us exactly
举例说,科学家能准确地告诉我们
when a space-capsule will arrive on the moon for instance,
宇宙密封小舱何时抵达月球
and exactly when it will return.
和何时返回.
They can calculate things like this to the nearest second.
对这类事情,他们的计算可精确至秒.
How do they do it?
他们是如何做的呢?
Well,of course,they use mathematics.
当然他们运用了数学.
We can all do simple sums on paper,
我们都能在纸上做简单的算术题,
but we must use computers for extremely difficult calculations.
但必须用计算机进行复杂的运算.
Perhaps you have seen mechanical calculating-machines in banks and offices.
你也许在银行和办公室见过机械计算机.
They can work very quickly,but nothing like computers.
尽管它们运算迅速,但与电子计算机截然不同.
Computers aren't mechanical.
电子计算机不是机械的.
They don't have wheels and gears in them.
它们没有转轮和齿轮.
Instead,they work on electrical circuits
而是通过电路工作的,
and can do difficult calculations at tremendous speed.
可以迅速进行复杂的运算
They can work 100 million times faster than the human mind!
它们运算速度要比人脑快上一亿倍.