Day 15: Seismograph
Cold start with the challenges
a terrible thing when the Earth rocks and rolls,
Earthquakes spread out and chaos unfolds
All things are impermanent that much can be seen
From atoms to mountains just part of the shifting scene
A bridge swing motion is not difficult to detect
But shifting granite and bedrock even explosives neglect.
gives us our challenges for the third program of the series. Kathy and
I have a seismograph challenge and they tell us that on day 3 we can test
it in a quarry with explosives!!
Kathy and I make up
a basic "pendulum" machine/instrument. This is basically a
heavy weight suspended and able to move from side to side. In actual fact,
if the Earth moves the idea is that the weight doesn't move and so there
is a relative motion between them that can be measured. We are not sure,
however, if it will be sensitive enough to pick-up an explosion in the
quarry. After all it can only measure the amount by which the Earth moves,
and this is a lot for an earthquake proper but won't be much for a few
sticks of dynamite however loud the explosion.
To make a record of
the results we take a clock apart and attach a paper disc to the minute
hand. In principle then this should turn the paper 360 degrees in 1 hour.
This records nicely, but there is a problem sometimes getting the paper
to be level and this leads to the chart recording dropping off the paper/not
Tomorrow we are going
to put the prototype onto the Franz Josef Bridge and record the movement
due to the traffic going across. Also think about an electronic circuit
to boost the sensitivity.
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