Jonathan Hare's Bugs and Barometers diary, from the BBC/OU series Rough Science 2
Day 1
The w(h)eather or not challenge
Felt disappointed and even slightly confused about the challenge from the start. Even if we can make the equipment in 1-2 days what good are only 1-2 days of observations? This needed some talking about and I don't think it ever happened properly - it's probably the only challenge where I felt things were not feasible from the start. So what did they actually want?
Mike B and I started to design and make up some of the various bits and pieces that a weather station might use. Barometer, hydrometer, wind speed device, rain gauge, thermometer etc.
I started on the barometer. Made up a U tube with water and used it to show Kate that the air pressure is due to the weight of air above our heads pressing down. So we go to the top of the lime factory and set the barometer and then go down to the sea and notice that the water level in the device has changed.
Now the density of air is about 1000 times less than water. So we need 1000 times less water height to balance the same mass of air. So by going 10m up (or down) in height the water barometer should change by 10m / 1000 = 0.01m = about 1cm, which it did - lovely piece of science. Can use this to measure the rough height of mountains etc.
Start on the wind speed / direction device. I spend too long trying to get the first design to work. The design works like this:
There is a flap that is attached to a wind vane. The vane makes sure the flap is always pointing into the wind. As the wind blows, it pushes the flap which by a string and lever mechanism moves a pointer fixed on the support pole. The problem which I wasted so much time on was how to get the pointer mechanism to move around with the rest of the gear and still work OK.
After several hours I drop this design for the more usual spinning half ball design. This worked very well (although the wind was sporadic and not good for testing it!) but how to get a scale or metre set up on it?
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Content last updated: 26/07/2006
