Using a barometer, how high is this tower?

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Using a barometer, how high is this tower? #1588501 13/11/2016 12:00 13/11/2016 12:00
Joined: Dec 2005 Posts: 33,556 Berlin barnacle OP Club Member 18 - ex-Minister without Portfolio
barnacle OP Club Member 18 - ex-Minister without Portfolio Forum Demigod Joined: Dec 2005 Posts: 33,556 Berlin	Let's see some suggestions - I'll start with some obvious ones: 1) find the architect and say 'Tell me how high the tower is and I'll give you this fine barometer' 2) use the barometer as a measuring stick 3) stand the barometer in the shadow of the tower and use the principle of equal triangles 4) make the barometer the bob of a pendulum and calculate the height from the period of the pendulum Last edited by barnacle; 13/11/2016 12:01. Reason: I have of course ignored the most obvious! Don't get no respect! Coupe Fiat 1994-2000 - an owner's guide <-- clicky!

Re: Using a barometer, how high is this tower? [Re: barnacle] #1588503 13/11/2016 12:31 13/11/2016 12:31
Joined: Dec 2005 Posts: 17,367 Staffordshire Nigel Forum veteran
Nigel Forum veteran Joined: Dec 2005 Posts: 17,367 Staffordshire	5) drop the barometer from the top of the tower and count (followed by a lengthy period of barometer parts retrieval) 6) put the barometer on ebay and buy a tape measure

Re: Using a barometer, how high is this tower? [Re: barnacle] #1588507 13/11/2016 13:18 13/11/2016 13:18
Joined: Mar 2007 Posts: 16,792 Auld Reekie Edinburgh Club President, member225
Edinburgh Club President, member225 Forum veteran Joined: Mar 2007 Posts: 16,792 Auld Reekie	I think you've raised the bar on this occasion Neil. Where's the bar? Judging by the December Saturday nights I've seen in Carlisle over the years most folk would fail a barometer test. BumbleBee carer

Re: Using a barometer, how high is this tower? [Re: barnacle] #1588528 13/11/2016 18:49 13/11/2016 18:49
Joined: Aug 2011 Posts: 2,595 angus, scotland jimbob13 I need some sleep
jimbob13 I need some sleep Joined: Aug 2011 Posts: 2,595 angus, scotland	Aren't a barometer and a pressure altimeter the same thing?

Re: Using a barometer, how high is this tower? [Re: barnacle] #1588532 13/11/2016 19:22 13/11/2016 19:22
Joined: Dec 2005 Posts: 9,706 Gone J Jimbo Je suis un Coupé
Jimbo Je suis un Coupé J Joined: Dec 2005 Posts: 9,706 Gone	What's the barometer measuring in, inHg? You could always subtract the pressure readings from top and bottom of the tower but I guess you'll need temperature too to be anywhere near mildly accurate.

Re: Using a barometer, how high is this tower? [Re: barnacle] #1588534 13/11/2016 19:22 13/11/2016 19:22
Joined: Dec 2005 Posts: 21,513 Aldershot PeteP Hon Club Member 005, Membership Secretary
PeteP Hon Club Member 005, Membership Secretary Forum Fossil Joined: Dec 2005 Posts: 21,513 Aldershot	Originally Posted By: jimbob13 Aren't a barometer and a pressure altimeter the same thing? Yes, just different dials but they work on the same principle, measuring atmospheric pressure. Last edited by PeteP; 13/11/2016 19:23. 16VT and X1/9 1500 We must all do our part for the planet. I unplugged a row of electric cars that nobody was using.

Re: Using a barometer, how high is this tower? [Re: barnacle] #1588563 13/11/2016 23:56 13/11/2016 23:56
F FreakinFreak Unregistered
FreakinFreak Unregistered F	Commission the the largest barometer ever built - the size of the tower, and get them to send over the specs. Lunch.

Re: Using a barometer, how high is this tower? [Re: barnacle] #1588607 14/11/2016 18:18 14/11/2016 18:18
Joined: Dec 2005 Posts: 754 The South of the West JonH Enjoying the ride
JonH Enjoying the ride Joined: Dec 2005 Posts: 754 The South of the West	Unfortunately by the time you've ascended the tower to take reading number two (assuming reading number one at the base) odds are that atmospheric pressure will have varied naturally anyway, introducing error on the comparative result. Whilst recognising Ignoring the issues of gravity You'd need two barometers to relate to each other, leave one at the tower base and take one up with you, and take readings at specific identical times before doing the appropriate calculations. And you'll need two watches or other timing devices as well !!! Last edited by JonH; 14/11/2016 18:51. No.199

Re: Using a barometer, how high is this tower? [Re: barnacle] #1588617 14/11/2016 20:03 14/11/2016 20:03
Joined: Dec 2005 Posts: 33,556 Berlin barnacle OP Club Member 18 - ex-Minister without Portfolio
barnacle OP Club Member 18 - ex-Minister without Portfolio Forum Demigod Joined: Dec 2005 Posts: 33,556 Berlin	Here's two: weigh the barometer at ground level, and weigh it again at the top of the tower; use the change in weight to calculate the gravity and therefore the distance from the centre of the earth. Or, in a similar vein, use the barometer as a pendulum, measure the period, take it to the top and observe the difference in period; again, this tells you the gravity at the top and the bottom. JohH, if you choose a calm sunny high-pressure day, you'll find that the pressure is likely to change by only fractions of a millibar over the course of the day. The rate of change of pressure with altitude is much greater. (For what it's worth, I have an aneroid barometer on the wall which was made in 1917 and is quite capable of noting the pressure difference between the floor and the ceiling. According to it, Hemel moves up and down by several hundred feet from time to time!) Last edited by barnacle; 14/11/2016 20:04. Don't get no respect! Coupe Fiat 1994-2000 - an owner's guide <-- clicky!

Re: Using a barometer, how high is this tower? [Re: barnacle] #1588618 14/11/2016 20:11 14/11/2016 20:11
Joined: Mar 2007 Posts: 16,792 Auld Reekie Edinburgh Club President, member225
Edinburgh Club President, member225 Forum veteran Joined: Mar 2007 Posts: 16,792 Auld Reekie	Are you re-measuring St Mary's spire Neil? BumbleBee carer

Re: Using a barometer, how high is this tower? [Re: barnacle] #1588619 14/11/2016 20:19 14/11/2016 20:19
Joined: Dec 2006 Posts: 3,927 The Faringdon Folly O oxfordSteve Forum is my job
oxfordSteve Forum is my job O Joined: Dec 2006 Posts: 3,927 The Faringdon Folly	Ah, but if all you have is a barometer and the tower, how do you propose measuring the period of the pendulum.....or indeed tie it to anything?

Re: Using a barometer, how high is this tower? [Re: barnacle] #1588620 14/11/2016 20:23 14/11/2016 20:23
Joined: Dec 2005 Posts: 754 The South of the West JonH Enjoying the ride
JonH Enjoying the ride Joined: Dec 2005 Posts: 754 The South of the West	Originally Posted By: barnacle Here's two: weigh the barometer at ground level, and weigh it again at the top of the tower; use the change in weight to calculate the gravity and therefore the distance from the centre of the earth. Or, in a similar vein, use the barometer as a pendulum, measure the period, take it to the top and observe the difference in period; again, this tells you the gravity at the top and the bottom. JohH, if you choose a calm sunny high-pressure day, you'll find that the pressure is likely to change by only fractions of a millibar over the course of the day. The rate of change of pressure with altitude is much greater. (For what it's worth, I have an aneroid barometer on the wall which was made in 1917 and is quite capable of noting the pressure difference between the floor and the ceiling. According to it, Hemel moves up and down by several hundred feet from time to time!) Agreed the differance in fractions of millibars is small but it depends how accurate you a want the height to be determined. And gravity is affected by earth tides so again time differances in measurements can make a differance to the final calculated figures. It sucks ! No.199

Re: Using a barometer, how high is this tower? [Re: barnacle] #1588626 14/11/2016 21:46 14/11/2016 21:46
Joined: Dec 2005 Posts: 33,556 Berlin barnacle OP Club Member 18 - ex-Minister without Portfolio
barnacle OP Club Member 18 - ex-Minister without Portfolio Forum Demigod Joined: Dec 2005 Posts: 33,556 Berlin	Well, I guess we'd better hope that it's a mercury barometer from which we can McGyver a laser rangefinder... The change of pressure with height, close to sea level, is around 27mmHg/1000ft - call it 0.1mBar/meter. It slows down as you get higher; there's less air sitting on top. Last edited by barnacle; 14/11/2016 21:46. Don't get no respect! Coupe Fiat 1994-2000 - an owner's guide <-- clicky!

Re: Using a barometer, how high is this tower? [Re: barnacle] #1588881 18/11/2016 00:52 18/11/2016 00:52
N NuIotaChi Unregistered
NuIotaChi Unregistered N	Go up the tower with the barometer and a high speed camera. Wait till some smartarse yells "What's the weather like up there?". Record the whole thing on the camera and then analyse the time delay between the audio and video.

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