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Question: How will you determine the height of a building with the aid of a barometer?

Student's Answer: Tie a long rope to the neck of the barometer and lower it to the street from the top of the building. The length of the rope used added to the height of the barometer gives the height of the building.

While the student claimed full marks for this answer, the examiner had his own doubts. The matter was raised with the University and an independent arbiter was appointed to judge the case. The arbiter realised that though the student had a fair case, the answer he had given didn't establish his competence in Physics. He therefore suggested giving the student six minutes to come up with an answer, making it clear that the answer should reflect his knowledge in Physics. Five minutes into the allotted time and the student still hadn't written anything.

"Would you like to give up?" asked the arbiter. "No. I have many answers to this problem. I was just wondering which one would be the best," the student replied. In the last minute, he seemed to make up his mind and wrote down an answer. It read: "Take the barometer to the top of the building, drop it over the edge, measuring the time it takes to reach the ground. The height can now be found using the formula h = 1/2 g (t)^2."

The arbiter asked the examiner if he was satisfied with this answer and he conceded. Just as the arbiter was about to leave, he remembered that the student had said he had many answers to the same problem. He asked the student what they were. "On a sunny day you could measure the height of the barometer, the length of its shadow and the length of the shadow of the building. Using simple proportion, the building's height can be determined."

"Fine," said the arbiter, "and the others?"

"Yes," said the student, "there is a basic measurement method which is very direct. You would have to take to the staircase, marking off the height of the building in barometer lengths and adding them in the end."

"But if you wanted to be highly scientific about it," continued the student, "you could tie the barometer to the end of a string, swing it as a pendulum, and determine the value of g (gravity) at the ground level and at the top. Using the difference in the value of g, the height of the building, in principle, can be calculated."

"There are many other ways to solve this problem. Probably the best way," he said with a gleam in his eye, "would be to knock on the caretaker's door and tell him 'If you would like a fine new barometer, I will give you this one if you tell me the height of this building."

"Do you really not know the conventional answer to this question?" asked the arbiter at this point.

"If you merely wanted to be boring and orthodox about it, of course, you could use the barometer to measure the air pressure at the top and ground level, and convert the difference in millibars into feet to give the height of the building," completed the student. He admitted to having known this answer and that he was fed up with instructors trying to teach him how to think.

The arbiter in this incident is Ernest Rutherford, who went on to play an influential role in the student's life. The student in question is none other than Niels Bohr, who improved upon Rutherford's atomic model. Bohr, who won the Nobel Prize in Physics in 1922, is known best for his contributions in understanding quantum mechanics and atomic structure. Did this really happen? Or is it merely a figment of imagination that has gone on to become an urban legend? Without the right facts, these things are certainly debatable.

What we do know is that a conventional answer need not always be the only correct answer. A little bit of thought might give us a solution which is simpler and more elegant. Are there more ways to determine the height of a building using a barometer? You know better!