A teacher asks a student how he would measure the height of a very tall
building using a barometer, evidently expecting to hear about the
reduced air pressure being proportionate to the elevation ….

The student replies: Tie the barometer to a long string, lower the
string till the barometer touches the ground, measure the length of the
string !

However, what follows is much more interesting: This highly original
answer so incensed the examiner that the student was failed.

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 five 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 its 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 at 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 square root (l/g).” ” 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 boring and orthodox 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
into 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 skyscraper’ .”

The student was Niels Bohr, the only person from Denmark to win the
Nobel Prize for Physics.