The following concerns a question in a physics degree exam at the
University of Copenhagen:
"Describe how to determine the height of a skyscraper with a barometer."
One student replied: "You tie a long piece of string to the neck of the
barometer, then lower the barometer from the roof of the skyscraper to the
ground. The length of the string plus the length of the barometer will
equal the height of the building."
This answer so incensed the examiner that the student was failed
immediately. The student appealed on the grounds that his answer was
indisputably correct, and the university appointed an independent arbiter
to decide the case. The arbiter judged that the answer was indeed correct,
but did not display any noticeable knowledge of physics. To resolve the
problem, it was decided to call the student in and allow him six minutes in
which to provide a verbal answer, which showed at least a minimal
familiarity with the basic principles of physics.
For 5 minutes, the student sat in silence, forehead creased in thought.
The arbiter reminded him that time was running out, to which the student
replied that he had several extremely relevant answers, but couldn't make
up his mind which to use. On being advised to hurry up, the student
replied as follows:
"Firstly, you could take the barometer up to the roof of the skyscraper,
drop it over the edge, and measure the time it takes to reach the ground.
The height of the building can then be worked out from the formula H= 0.5g
x t squared. But bad luck on the barometer.
"Or, if the sun is shining you could measure the height of the barometer,
then set it on end and measure the length of the shadow. Then you measure
the length of the skyscraper's shadow, and thereafter it is a simple matter
of proportional arithmetic to work out the height of the skyscraper.
"But, if you wanted to be highly scientific about it, you could tie a short
piece of string to the barometer and swing it like a pendulum, first as
ground level and then on the roof of the skyscraper. The height is worked
out by the difference in the gravitational restoring force T = 2 pi sq root
"Or if the skyscraper has an outside emergency staircase, it would be
easier to walk up it and mark off the height of the skyscraper in barometer
lengths, then add them up.
"If you merely wanted to be orthodox and boring about it, of course, you
could use the barometer to measure the air pressure on the roof of the
skyscraper and on the ground, and convert the difference in millibars to
feet to give the height of the building.
"But since we are constantly being exhorted to exercise independence of
mind and apply scientific methods, undoubtedly the best way would be to
knock on the janitor's door and say to him, 'If you would like a nice new
barometer, I will give you this one if you tell me the height of this
The student was Niels Bohr, the only Dane to win the Nobel Prize for
Physics. (In 1922, "for his services in the investigation of the structure of atoms and of the radiation emanating from them")
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