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On Monday, January 5, 2004, at 05:49 PM, Murray Campbell wrote:

> harmonic resonance and amplify the tides considerably

Another off-topic story... about constructive interference of harmonic
motion.

I was in High School in California in the mid 1970s where our physics
teacher Mr. McCartney, at the end of the school year told us to meet
for physics class at the Olympic swimming pool at our High School.  We
were to come in our swimming suits.  We thought that this would be a
fun last day of school, an easy day.

When we arrived we learned it was to be a physics experiment.  Our
teacher had half of the class stand at one end of the Olympic pool, and
the other half of the class stood 50 yards away at the other end of the
pool.  The pool was about 5-6 feet deep, constant depth from end to end.

He had half of our class jump in at one end of the pool, everybody all
at once.  It created a wave that slowly moved down the pool to the
other end.  When it reached the end and crested against the opposite
end of the pool, the people at that end jumped in on top of the wave,
and simultaneously the people at the other end got out.

The result was a slightly bigger wave heading back to the start again.
We did this four or five times and got a pretty nice wave going.  By
this time class was over, and we had all learned about constructive
interference of waves.  Class dismissed.

It turns out that many of us had Physical Education (PE) class right
afterwards, and this being the end of the year (June), PE was swimming
once again.  (The girls would sunbathe around the Olympic pool while
most of the guys would jump off of the diving boards in the large
diving pool next to the Olympic pool.  Homestead High School in
Sunnyvale California was a great school.  This is where Steve Jobs and
Steve Wozniak went to High school just a few years earlier.  These
founders of Apple had a history of pranks which we had inherited, but I
am getting ahead of the story...)

The physics teacher and part of the class left to get changed and head
to their next period.  A bunch of us who had PE next just stayed and
continued the project.  As our fellow PE students arrived, we educated
them about constructive interference and they joined our new physics
project.

The time between when the physics teacher left and the PE teacher
arrived was sufficiently long that we got a very large wave going
without any teachers around.  The waves began breaking out of the pool
and huge quantities of water began flooding the pool area.  In 20
minutes of unsupervised time, we knocked two-thirds of the water out of
the pool, which for a 50 yard by 25 yard by 2 yard pool is
approximately 335,000 gallons of water!!

The experiment was never allowed to take place again and we all got in
trouble of course, but I bet none of us ever forgot the power of
constructive interference of harmonic waves over time.  It was the best
physics experiment I ever got to participate in.

Thank you Mr. McCartney!

Dan

   

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