From: hal@finney.org
Date: Mon Dec 20 1999 - 16:38:14 MST
Dan Fabulich asks:
> Say, does anybody here know how to demonstrate to a layman that the earth
> revolves around the sun rather than vice versa? I realized the other day
> that I didn't know how, and that this was arguably the sort of experiment
> which everybody ought to do/see/be aware of at some point in their lives.
I believe that historically this fact was established by observing that
planetary motions could be better explained by assuming that they go
around the sun rather than around the earth. Detailed observations then
let Kepler derive his three laws which established that the planets had
eliptical orbits with certain shapes and speeds. Given all this it is
simplest to assume that earth, like the other planets, orbits the sun.
The best way to get this raw data is to plot the position of a bright
planet over a period of time. Mars is a good example as it tends to show
the retrograde motion which was so puzzling to the ancients - forward,
then backward, then forward again.
Hal
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