Sir Ernest Rutherford, President of the Royal Academy, and
recipient of the Nobel Prize in Physics, related the following
story:
Some time ago 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.
I read the examination question: "Show how it is possible
to determine the height of a tall building with the aid of a
barometer."
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!
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.
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
off 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 stopwatch. Then, using the formula x=0.5*a*t^2, 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 proportion, 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. 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."
"On this same tack, 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
precession."
"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's door. When the superintendent answers, you speak
to him as follows: 'Mr. Superintendent, here is a fine barometer.
If you will 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.
The name of the student was Niels Bohr." (1885-1962) Danish
Physicist; Nobel Prize 1922; best known for proposing the first
'model' of the atom with protons & neutrons, and various
energy state of the surrounding electrons -- the familiar icon
of the small nucleus circled by three elliptical orbits ... but
more significantly, an innovator in Quantum Theory.
Is
this true?
