最好的答案不一定最标准，考试如此，人生也常常如此。

One day I received a call from a colleague. He was about to give a student a zero for his answer to a physics question, while the student claimed a perfect score. The instructor and the student agreed to an impartial arbiter, and I was selected.2 I read the examination question: "Show how it is possible to determine the height of a tall building with the aid of a barometer3." The student had answered: "Take the barometer to the top of the building, attach a long rope to it, lower it to the street, and then bring it up, measuring the length of the rope. The length of the rope is the height of the building."

The student really had a strong case for full credit since he had really answered the question completely and correctly!4 On the other hand, if full credit were given, it could well contribute to a high grade in his physics course and certify competence in physics, but the answer did not confirm this.5 I suggested that the student have another try. I gave the student six minutes to answer the question with the warning that the answer should show some knowledge of physics. At the end of five minutes, he hadn't written anything. I asked if he wished to give up, but he said he had many answers to this problem; he was just thinking of the best one. I excused myself for interrupting him and asked him to please go on. In the next minute, he dashed off6 his answer, which read: "Take the barometer to the top of the building and lean over the edge of the roof. Drop the barometer, timing its fall with a stopwatch7. Then, using the formula x=0.5×a×t2, 8 calculate the height of the building."

At this point, I asked my colleague if he would give up. He conceded, and gave the student almost full credit. While leaving my colleague's office, I recalled that the student had said that he had other answers to the problem, so I asked him what they were. "Well," said the student, "there are many ways of getting the height of a tall building with the aid of a barometer. For example, you could take the barometer out on a sunny day and measure the height of the barometer, the length of its shadow, and the length of the shadow of the building, and by the use of simple proportion9, determine the height of the building."

"Fine," I said, "and others?"

"Yes," said the student, "there is a very basic measurement method you will like. In this method, you take the barometer and begin to walk up the stairs. As you climb the stairs, you mark off the length of the barometer along the wall.10 You then count the number of marks, and this will give you the height of the building in barometer units."

"A very direct method."

"Of course. If you want a more sophisticated method, you can tie the barometer to the end of a string, swing it as a pendulum, and determine the value of g [gravity] at the street level and at the top of the building. From the difference between the two values of g, the height of the building, in principle, can be calculated.11

"On this same tack,12 you could take the barometer to the top of the building, attach a long rope to it, lower it to just above the street, and then swing it as a pendulum. You could then calculate the height of the building by the period of the precession13.

"Finally," he concluded, "there are many other ways of solving the problem."

"Probably the best," he said, "is to take the barometer to the basement and knock on the superintendent's14 door. When the superintendent answers, you speak to him as follows: 'Mr. Superintendent, here is a fine barometer. If you tell me the height of the building, I will give you this barometer."

At this point, I asked the student if he really did not know the conventional answer to this question. He admitted that he did, but said that he was fed up with high school and college instructors trying to teach him how to think.15 The name of the student was Niels Bohr16.

1. 卢瑟福（1871－1937），英国物理学家，生于新西兰， 因对元素衰变的研究获1908年诺贝尔化学奖。

2. 师生俩决定找一位不偏不倚的裁判，于是选中了我。arbiter：裁决人，决定者。

3. barometer：气压计。

4. 这位学生的确有充分的理由得满分，因为他的回答严丝合缝准确无误。

5. 但从另一方面看，如果给满分，无疑会令他的物理课成绩优异从而表明他在物理学方面能力突出，但这个答案并不能证实这一点。

6. dash off：迅速写（或画），迅速完成。

7. 用秒表记录它下落的时间。

8. 自由落体公式：高度＝0.5×重力加速度×时间的平方。

9. 通过运用简单的比例法。

10. 你在墙上依次标出气压计的长度。 这种方法简言之就是用气压计当尺子去量大楼的高度。

11. 还有一种更复杂的方法，你可以把气压计系在绳子的一端，让它像摆锤一样摆动，分别测算出在地面和楼顶上的重力加速度g。理论上，根据这两个g的差值就可以计算出建筑物的高度。

12. 根据同样方法。

13. period of the precession: 摆动周期。

14. superintendent：<美>管房人，看门人。

15. 他说从中学到大学， 老师们总是试图教他怎样去思考，对此他实在感到很腻烦。

16. Niels Bohr: 玻尔（1885－1962），丹麦物理学家，因对原子结构的研究获1922年诺贝尔物理学奖。