Is This Barometer Height Question a Hoax?

[ZapperZ]

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

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.

 

[chroot]

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]

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]

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]

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]

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]

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]

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]

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]

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).

 

[Evo]

Here's a popular version

http://www.squ.edu.om/Sci/Phys/general/tempnews/story1b.html

tons of versions on google http://www.google.com/search?hl=en&...ith+the+aid+of+a+barometer&btnG=Google+Search

 

[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...

 

[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]

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]

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.

 

[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]

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.

 

[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!)

 

[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...).

 

[moose]

10. Give the barometer to someone and instruct them to stand at the bottom. Have the shout a quick "HEY!" (or whatever) and wave the barometer at the same time. Measure to time from the wave until you hear their shout.

 

[Rach3]

11. Melt the barometer, and draw the hot metal into a long, thin steel wire. Attaching the remainder of the barometer metal as a weight, lower the wire over the edge of the top of the building. When the barometer hits the ground, mark off a point on the wire, then draw it back up and measure the length.

 

[Rach3]

12. Look at the barometer. Is it intelligently designed? Yes, it is! Therefore, at least one omnipresent god exists; invoke this deity with prayers and offers of barometers, until the dimensions of the building are revealed to you in a dream. (7 cubits x 14 cubits x 70 cubits, as it were.)

 

[Rach3]

13. Shatter your barometer with a hammer. Pick out the longest, sturdiest pieces of steel, and using them as traction spikes, climb up the side of the building, while drawing out a long tape measure.

 

[Danger]

You could attach a variable resistor to the dial and measure the voltage difference between the top and bottom of the building.

 

[dontdisturbmycircles]

Camp out until the window cleaners come, weeks if necessary. Ask if you may borrow their seat/rope for a while, carefully remove one side of the barometer to make markings with. As you go down the building, tick off lengths of the barometer until you are at the bottom. Upon reaching the bottom you can say "The building is X barometers tall."

 

[nannoh]

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.

I hear the Physics Forums is owned by the Scientologists now!

 

[dontdisturbmycircles]

lol woops berkeman already came up with my idea. doh.

 

[Severian]

If I had been marking that he would have gotten zero marks right at the start, and no opportunity to resit. He was asked to use a barometer to measure the height, when in fact he used a piece of string. So the first answer is just plain wrong.

 

[-Job-]

12. Look at the barometer. Is it intelligently designed? Yes, it is! Therefore, at least one omnipresent god exists; invoke this deity with prayers and offers of barometers, until the dimensions of the building are revealed to you in a dream. (7 cubits x 14 cubits x 70 cubits, as it were.)

Yes, but that would only work x% of the time, and i think the problem asks for a definite solution.

 

[Delzac]

But anyway, if a student were to really write such interesting answer, will he be awarded full credit?

 

[Danger]

Yes, but the marks will be hidden and he'll be required to discern their location using a bowling ball and an eyedropper.

 

[Aether]

This is supposedly a "message" from a physics professor...I believe that this is a hoax and something someone made up...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.

The author of the article doesn't claim to be a physics professor, but rather he appears to identify himself as "A Washington-based Economist". The entire column is in quotations and it is presented as "A message from a Physics Prof". The author may have actually received this from a "Physics Prof", or he may have some other good faith basis to believe that this is a message from a person of this description. I would ask for a clarification of exactly what the author is claiming before making an accusation that he could easily explain away in any number of ways.