Day 15: Seismograph

Bright, cold, gorgeous day again. Around a fire - Kate tells us challenges. Mike B and Mike L to spend night in a tent - to seek gold in rock in mountains. Ellen to help make a waterproof tent... and it's got so cold now! Rather them than me!

Jonathan and I are making a seismograph. We made amazing progress in a day. It's built. But whether it will measure any tremor (or even a full blown mother of an earthquake) - we have NO idea. It's all relying on trying to get something to move a different way - to something that's jiggling in the moving earth. So a suspended bit of metal — with a huge weight attached. SHOULD move differently from the jiggling earth. But - if the earth only moves a few mm that's about the distance we'll have to detect... and 3 mm is a pretty big move, for something as heavy as the earth to make. Thankfully - Kate tells us - we'll test the seismometer with dynamite... but even THEN I suspect we won't do that much. Usually, for these challenges, someone somewhere has tested it out just to be sure it's fair and feasible... but not this one. It's possible dynamite moves rock very differently from the way an earthquake does. Quite likely really! Our seismograph reading detects motion in one plane - so we're assuming there will be some motion in that plate!

To test it out - we're "taking it to the bridge" tomorrow. The bridge is the jiggliest thing around.... When trucks go over it moves quite a bit. If we can get some reading tomorrow we can test out the sensitivity of our seismographs - and try to tweak it to improve it. But we may get no reading at all from the bridge, after all - it tends to move vertically up and down when cars go over - and we're looking at a sideways move. But I'm worried our reading from the dynamite will be spectacularly underwhelming. So - actually - our bridge measurements - IF we get any! - may be the most spectacular we get!

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