## 27 Ways to Use a Barometer to Find the Height of a Building by Douglas Grimm

1. Tie a long piece of string to the barometer. Hold one end of the string from the top of the building, so that the end of the barometer barely clears the ground. Give the barometer a small displacement and time its period as a compound pendulum.
2. Smash the barometer on the roof of the building and time how long it takes for the mercury to drip down the wall of the building to the ground. Use the known viscosity of mercury to find the velocity.
3. Throw the barometer horizontally off the building with a known velocity (calibrate your throwing ability by timing and measuring barometer throws on the ground). Use projectile motion to find the height of the building once the distance the barometer lands from the building is found.
4. Find a small, very efficient, very light electric motor. Weigh the barometer. Use the motor to carry the barometer up the building. Using a voltmeter and ammeter, calculate the work done by the motor, and thus the gravitational potential difference between the top and bottom of the building. Knowing g, find the height.
5. Go to the basement. Find a part of the basement such that directly above you is solid brick until you reach the roof. Throw the barometer at the ceiling of the basement, which is the floor of the building. The barometer will most likely bounce off the floor. Repeat n times, where n is a very large number. In a few trials, the barometer will tunnel through the potential field of the bricks, and appear on the top of the building. Calculate the percentage of trials for which the barometer tunnels. Use the quantum tunneling equation to calculate the length of the barrier, and thus the height of the building. Note: this effect can be calibrated properly by finding the likelyhood of the barometer tunneling through one brick.
6. Attach a copper wire to the top of the building, and attach the other end to the ground. Smash the barometer and use one of the shards of glass to cut the wire halfway up the building and place an ammeter in series with the wire. Knowing the current through the wire and the resistivity of copper, the potential difference between the top of the building and the bottom of the building can be found. This will be a gravitational potential difference, not an electrical one, but the electrons don't know that. Thus, since g is known, the height of the building can be found.
7. Find a large wooden rod a bit longer than the building is high. Wrap an insulated copper wire around this rod at a uniform turn density. Make the coil stop at the top and bottom of the building. Run alternating current through the coil, measure current and voltage, and determine the inductance of the coil. Place the barometer in series with the coil so the resistance of the circuit is enough to stop the wires from melting. With the inductance of the coil and its turns per unit length and radius, the length of the coil, and thus the height of the building, can be found.
8. Drop the barometer off the top of the building and measure the radius of the resulting puddle of mercury.
9. Using a device that can propel an object at a known velocity (such as a baseball pitching machine or a rail gun), find the escape velocity of the barometer from the ground, after first having tied a string to the barometer so it can be retrieved from deep space. Repeat on the top of the building. The difference in escape velocity energies gives the gravitational potential difference between the ground and the roof, thus yielding the height.
10. Using the aforementioned pitching machine or rail gun, find the velocity at which the barometer needs to be projected to reach the roof from the ground.
11. Make a small hole in the barometer through which mercury drips at a constant rate. Time this rate at the ground. Place the barometer on the roof and observe the drip rate from the ground with binoculars. The drip rate will be dilated, by general relativity, by a factor which will give the difference in the curvature of space at the bottom and top of the building. Knowing the mass and radius of the earth and so on, the height of the building can be found.
12. THIS METHOD USES MORE THAN ONE BAROMETER: Pack as many barometers as possible into the building until it undergoes gravitational collapse and becomes a black hole. Knowing the number of barometers used, the mass of this hole can be calculated, and the Schwarzchild radius of the hole is thus half the height of the building.
13. Find a barometer that uses a liquid with no surface tension whatsoever (superfluid helium?). Break the barometer and spread the liquid evenly over the surface of the building. Measure the depth of the resulting liquid film. Knowing the volume of the barometer, this gives the surface area of the building, which will give its height, if its width and depth are known.
14. Stand on the roof of the building. Throw the barometer to a point exactly on the horizon. Measure the distance from the bottom of the building to the barometer. This gives the horizon distance at the top of the building, thus giving its height above the ground.
15. Make a small hole in the barometer so mercury drips out at a constant rate. Place the barometer so that it is dripping off the roof onto the ground. Measure the time between a drop being released from the barometer and the drop hitting the ground. Repeat the measurement when moving towards the ground at a known velocity. The time between a drop being released and a drop hitting the ground will change. Using the Lorentz transformation equations and taking the top of the tower as x = 0, the position of the ground can be found. This will yield the height of the tower.
16. Find a steel cable. Attach it to the barometer and use the barometer as a physical pendulum to measure g. Then attach the building to the cable (after having remove it from its foundations and attaching the cable to a crane of some sort), and using the building as a physical pendulum, and knowing g, measure its moment of inertia. This will give the dimensions of the building and so on.
17. Use a barometer containing sulfuric acid. Break the barometer on the roof of the building and time how long it takes the acid to eat its way down to the ground.
18. Measure the volume of the barometer at the bottom and top of the building. By knowing the coefficient of thermal expansion of glass, the temperature difference between the top and bottom can be calculated. Refer this to known data of atmospheric temperature as a function of height.
19. Every time somebody walks into or out of the building, stab them with the sharpened end of the barometer (after having sharpened it, of course). Word of the 'Barometer Murderer' will eventually reach the building's owner, who will of course be forced to sell the building. The real estate advertisement should give the height of the building.
20. Knowing the density, width and length of the building, rip the building from its foundations and place it on top of the barometer, giving it a pressure equal to the building's weight divided by the measurement area of the barometer. Thus the weight, and so the height, of the building can be found.
21. Find the architect who designed the building, crack the (mercury) barometer over his coffee, watch him die when he drinks it, then steal the building's specifications, including height.
22. THIS ALSO REQUIRES MORE THAN ONE BAROMETER: knowing Young's Modulus for brick, place barometers on the roof until the roof is lowered by one barometer length. This change in the height of the building under a known stress and Young's Modulus will give the height of the building.
23. Place a cat on top of the building. Prod it with the barometer so that it falls off the roof. See whether the cat dies when it hits the ground. Repeat n times, where n>>{a large number}. Refer to Dr Karl Kruszelnicki's paper on the probability of a cat dying when falling from a certain height.
24. AGAIN, MORE THAN ONE BAROMETER: place as many barometers in the building as will fit. This gives the volume, thus the height, if other dimensions are known.
25. Use a machine (such as the aforementioned baseball pitching machine or rail gun) that can hurl the barometer down from the ground into a hole in the ground at a velocity that is only known to within a certain tolerance. Find the smallest uncertainty in velocity, and thus momentum, such that the barometer appears on top of the building. Use Heisenburg's position-momentum uncertainty relationship to find the height of the building.
26. Tie a string to the barometer and hang it as a plumb bob. The string will be slightly deflected from the vertical by the gravitational effect of the building. This gives the mass of the building, etc.
27. Find at what velocity you must move upwards or downwards past the building such that the building is contracted to the same length as the barometer. Find gamma for this velocity, multiply by the length of the barometer.

Sent by: posted on 16 February 2007