# I think I found a hoax

#### ZapperZ

Staff Emeritus
2018 Award
This is supposedly a "message" from a physics professor. Read it and then read the rest of this post.

http://www.centralchronicle.com/20061213/1312302.htm [Broken]

I believe that this is a hoax and something someone made up. This is because this was the same thing that Martin Gardner had asked a long time ago. In his book "Mathematical Magic Show" (Mathematical Association of America, 1989), he asked this exact question. On page 141, Question 23 asked "Give at least three ways a barometer can be used to determine the height of a tall building." In his answer, he gave 5:

1. Lower the barometer using a string from the roof and then measure the length of the string (this, btw, happens to correspond to the FIRST answer given by the "student" in that article).

2. Same as #1, but let it swing like a pendulum and measure the frequency or period.

3. Drop the barometer from the roof and measure the time taken.

4. On a sunny day, find the ratio of the height of the barometer to the height of the building

5. Find superitendent of the building, give him the barometer if he tells you the height of the building (this last answer happens to also correspond to the student's last answer. Coincidence? I don't think so.).

My conclusion: whoever wrote the article made up this story and that this scenario never happened. I'm waiting for enough people to read this as witnesses before I write an e-mail to whoever runs this thing.

Zz.

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#### chroot

Staff Emeritus
Gold Member
It's one of the oldest physics jokes around, man. I don't think anyone actually believes it happened. Besides, most versions of this joke attribute the antics to Heisenberg or Planck or some other luminary.

- Warren

#### dontdisturbmycircles

I have heard this one too. Although I only heard the drop the barometer and trade the barometer to the super intendant solution.

#### BobG

Homework Helper
I think the story was first told by Alexander Colandra in 1958. It was 'a physics student', not anyone famous (many versions identify a famous scientist, such as Neils Bohr, as the student). Whether the incident actually happened, or at least something close (class's smart-alec comments to a tolerant professor during class vs. on a test, for example), is unknown.

#### russ_watters

Mentor
Yeah, not a hoax, just a joke.

edit: well, if the columnist is claiming it happened to him, then that makes it a hoax.

#### ZapperZ

Staff Emeritus
2018 Award
Oh, I would HOPE people here have heard of it. However, this site seems to indicate as if this actually happened based on some real-life event, with no disclaimer of any kind to indicate that it's fiction. If this is a "news" publication, that is unethical.

Zz.

#### Danger

Gold Member
I too have heard some parts of that.
There is, however, one other possibility that you guys haven't mentioned. It's conceivable (however unlikely) that neither of those professors had ever heard it, but that a real student had and decided to act it out.

#### ZapperZ

Staff Emeritus
2018 Award
I too have heard some parts of that.
There is, however, one other possibility that you guys haven't mentioned. It's conceivable (however unlikely) that neither of those professors had ever heard it, but that a real student had and decided to act it out.
I don't believe so. How was the student to know in the very beginning that he would be given the opportunity to spew out all the different answers. He is also taking a very high risk of getting a zero for that question simply to act out something he read that was part of a "puzzle".

Zz.

#### berkeman

Mentor
4. On a sunny day, find the ratio of the height of the barometer to the height of the building
This can be done on a cloudy day as well. How many other ways can we think up?

6. Rappel down the side of the building, marking off increments of the barometer length.

#### Chi Meson

Homework Helper
I think the story was first told by Alexander Colandra in 1958. It was 'a physics student', not anyone famous (many versions identify a famous scientist, such as Neils Bohr, as the student). Whether the incident actually happened, or at least something close (class's smart-alec comments to a tolerant professor during class vs. on a test, for example), is unknown.
Their was a big discussion of the "Caladra Event" in a magazine ("The Physics Teacher" I think) a few years back. Calandra himself says that it happened with one of his students (in a less embelished form that the story has grown to). Evidently it can't be verified, so it remains in an unproven limbo. Having seen a lot of students making "clever-clever" answers (because they can't really solve the problem as expected) I fully believe that the original "Calandra" event did happen.

#### Danger

Gold Member
Maybe this is why I never finished high-school, but I would have done it just for the sake of controversy. In fact, I did do things like that in school (and never lost a dispute over it).

#### moose

When my english teacher asked me what the author of some book was thinking when she wrote the book, I replied "Probably that she was hungry and needed money, so she wrote a book".... Yeah, my teacher didn't like that very much for some reason...

R

#### Rach3

This can be done on a cloudy day as well. How many other ways can we think up?

6. Rappel down the side of the building, marking off increments of the barometer length.
7. Seal off the building's ventilation ducts, and put on your hazmat suit. Now, carefully shatter your barometer and collect the liquid mercury in a glass beaker. Weigh, and let it stand indoors for a few hours; weigh again. The difference in mass, multiplied by the vapor pressure of mercury at your building's temperature at atmospheric pressure, gives the interior volume of your building. You can thus determine the height by measuring the interior base dimensions, which can readily be done with a yardstick.

This experiment would benefit from strategically placing fans throughout the building, to help the mercury vapors diffuse.

#### ZapperZ

Staff Emeritus
2018 Award
Well, I think the issue here is slightly lost. WE here all know about this and have read it elsewhere. However, the "author" of this article didn't attribute it to anything, thus making it as if it is an original story or, worse still, that the scenario that was described actually happened. I'm not sure what kind of website this is (it appears to be a news article and that this was a contributed piece). Considering that most people that read it would not be proficient in physics and probably have not heard of this puzzle, they would be inclined to think that this actually happened.

Again, my original complaint was that this was rather an unethical thing to do.

Zz.

#### Evo

Mentor
Again, my original complaint was that this was rather an unethical thing to do.

Zz.
Yep, they took credit for it by not posting a source.

R

#### Rach3

8. Hurl the barometer from the top of the tall building, aiming for a large standing crowd. As the ambulance approaches, measure the doppler shift of the frequency of the sirens at several positions, while simultaneously recording the angle between the LOS (line of sight) to the ambulance and the vertical. Have a collaborator on the ground measure the speed of the ambulance with a police radar. The height of the building follows from simple trigonometry.

#### berkeman

Mentor
7. Seal off the building's ventilation ducts, and put on your hazmat suit. Now, carefully shatter your barometer and collect the liquid mercury in a glass beaker. Weigh, and let it stand indoors for a few hours; weigh again. The difference in mass, multiplied by the vapor pressure of mercury at your building's temperature at atmospheric pressure, gives the interior volume of your building.
Dang that's a good one. (Sorry for the parallel hijack, ZapperZ.)

But an improvement would be

7a. Begin by measuring the barometric pressure on each floor. Then perform Rach3's experiment, and use the pressure by floor to increase the accuracy of the height calculation.

R

#### Rach3

9. Set off a calibrated bomb at the base of the building, and use your barometer to measure the overpressure of the blast wave at the summit. Refer to the bomb calibration tables to get your building's height (the manufacturers did all the work for you!)

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R

#### Rach3

Dang that's a good one. (Sorry for the parallel hijack, ZapperZ.)

But an improvement would be

7a. Begin by measuring the barometric pressure on each floor. Then perform Rach3's experiment, and use the pressure by floor to increase the accuracy of the height calculation.
I imagine there are much bigger sources of error - bottlenecks in vapor diffusion, vapor condensation, vapor leaks to the outside, and departures from ideal building geometry (including the volume of interior walls...).

"I think I found a hoax"

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