The Barometer

[DbPhoenix 42]

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 and neutrons, and

various energy states of the surrounding electrons -- the familiar icon of the small nucleus

circled by three elliptical orbits... but more significantly, an innovator in Quantum Theory.

[Tams 20]

... now can you tell me how to use volume in trading?

[DbPhoenix 42]

  Tams said:

... now can you tell me how to use volume in trading?

 

http://www.traderslaboratory.com/forums/f131/volume-observation-5266.html

[boru 10]

  DbPhoenix said:

http://www.traderslaboratory.com/forums/f131/volume-observation-5266.html

 

pretty good, DbPhoenix I want to thank you and all the others for all your posts on this and all the other threads(especially wickoff) I have been reading as many threads as I can for the last month and I am struggling with this price/volume analysis. There are times when a bulb will light up (faintly) but just as soon I feel lost again.It seems the clearest indications are on retests of s/r at least that is when it seems the clearest to me.matinthehats thread is good maybe I'll just go read it again and hopefully something will break loose.Any suggestions would be appreciatted thanks

[boru 10]

sorry this probably wasn't the right place for this

[zdo 20]

Bohr makes a pretty case for indicators

[firewalker 10]

Thanks for the story.

 

But I think the Bohr part is turning out to be an "urban legend"...

Niels Bohr / On Being a Student

snopes.com: The Barometer Problem

 

Take nothing for granted, even if it comes from dbphoenix

 

fire-"pedantic"-walker

[DbPhoenix 42]

It may be. But I got this years ago and didn't particularly care who the student was. Or wasn't. I just thought it was very clever.

[Kiwi 16]

Yes, although Bohr worked with Rutherford to form their joint Bohr-Rutherford model of the atom this story placed them in contact while Bohr was still firmly at home. Their meeting late while Bohr was still a student was far to late in his training for such a simple question.

 

I was wondering (my first degree was in Physics and Rutherford was by far our most famous physicist) so did some googling. One of the best pages I found was a discussion on the problem itself:

 

Measuring height of building with barometer Text - Physics Forums Library

 

 

This apparently may have been the origin of the story (Dr Alexander Calandra):

ALEXANDER CALANDRA

 

I liked the "original"(?) last paragraph and its indication of the time of the stories origin. Actually it is a much more satisfying final paragraph.

 

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, to use the "scientific method", and to explore the deep inner logic of the subject in a pedantic way, as is often done in the new mathematics, rather than teaching him the structure of the subject. With this in mind, he decided to revive scholasticism as an academic lark to challenge the Sputnik-panicked classrooms of America.