Inge Frette wrote:
>
> Hello folks,
> anyone out there that knows whether this is a true story or
> an "urban legend" ?
>
> Inge
>
> >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.
Inge - I've seen this story about "a student" more than once in the past but this is the
first time I can recall that it's been connected with a famous physicist.
The last paragraph shows a limited knowledge of physics history. It was
Rutherford himself who established (on the basis of the experiments of his students
Geiger & Marsden) the planetary model of the atom. (& I don't know where the number 3
of the orbits comes from.) What Bohr did was to quantize the orbits for hydrogen (which
were circular - Sommerfeld treated the more general elliptical ones). & the neutron
didn't come along till ~20 years later after the work of Chadwick, another of
Rutherford's students.
I suspect that someone has taken what used to be a joke among physics teachers
and tried to turn it into an inspirational story.
Shalom,
George
George L. Murphy
gmurphy@raex.com
http://web.raex.com/~gmurphy/
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