Give this memory test a try. Mix up 52 playing cards. Now look at the top seven for a second. Can you remember them in order?
Players at the World Memory Championships can. In fact, the 2002 champion (冠军), Andi, memorized the order of 1196 cards after looking at them for only an hour! And a German girl, Lara, only ten years old, memorized 75 faces and names in fifteen minutes!
In 1987, a Japanese man, Mr. Tomoyori, wanted to prove that his memory was the best in the world by remembering by heart pi (π), a number in math which starts 3.14159…This number never repeats itself or ends. He recited pi to 40,000 decimal places (小数位). It took the fifty-five-year-old man more than twelve hours to say the numbers, but he did it without making a mistake!
To remember pi, Mr. Tomoyori connected each number with a sound. He then made up stories to help him remember the words he made from the sounds. In an interview after his achievement, he said, “I decided to go ahead and memorize the value of pi up to one thousand places. But it wasn't easy – in fact, it took me three years. To get to 40,000 decimal places it took me about ten years.”
Unluckily for Mr. Tomoyori, his record was broken in 1995, when another Japanese man, Mr. Goto, memorized pi to 42,195 places.
在定义域内零点的个数为
