There is a theory which states that if anyone ever discovers
exactly what the Universe is for and why it is here, it will
instantly disappear and be replaced by something even more
bizarre and inexplicable. There is another theory which
states that this has already happened.

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This legend, the truth of which is not necessarily related to
its value, 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: "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 highly original answer so incensed the examiner that the
student was failed immediately.

He 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 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 sq 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 pres-
sure 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 inde-
pendence 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 building'."

The student was Niels Bohr, the only Dane to win the Nobel
prize for Physics.