Francis Berthomieu

EAAE Summer School Working Group (France)


For millenniums, units of time were defined in astronomical terms, using the daily or annual movements of Sun or Earth. Hours were known since the antic Egyptians, minutes and seconds became necessary when the measurements got more and more


Length and distance units were more difficult to define in a universal way. In the eighteenth century, there were two favourite approaches to the definition of the standard unit of length. One of them suggested the use of a pendulum with a half-period of one second. The other defined the metre as one ten-millionth of the distance from the Equator to the North Pole… Astronomic and terrestrial measurements were done for this purpose.

This workshop aims to present some simple experiments, easy to do in the classroom and appointing some of the difficulties about the measurements:

We shall discover some historical documents and experiments related to time and distance measurements, showing the obvious relation between both physical quantities.

We shall do practical experiments about triangulation (How could be measured the size of the Earth?), about pendulum (Which is the length of the pendulum with a half-period of one second?), and we shall construct an original correspondence table between time and (light-) distances using the speed of light as connection.

Full version (PDF).


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