Day 15: Seismograph
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!
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!