Rod Engelsman wrote:
In addition, the metric system derives some units from more basic ones. A
second is the period of a pendulum that is one metre long.
Are you sure about that? I know that originally the metre was defined as 1
millionth (or ten millionth?) of the distance from the equator to the north
pole running through Paris. The definition of the second wasn't changed
AFAIK. The have both subsequently been redefined more accurately and to make
them more convenient to measure in a laboratory.
But if, as you say, a second and a metre are related that way it would have
to be an incredible coincidence.
I've tried to double-check, but I can't find a source. I calculated the
period of a 1-metre pendulum and I got 2.0064 seconds. So a single swing
of the pendulum would be 1.0032 seconds. That error, while small, seems
hard to explain by anything other than assuming that the definition of a
second was never a metre and that this is all one big coincidence.
Very interesting indeed.
So, maybe I was taught years ago that a second is a sing if a 1-metre
pendulum and I mistook this to be an original definition.
Daniel.
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