On Saturday, February 9, 2019 at 3:29:55 AM UTC-7, Gerald Kelleher wrote:

In more technical language, this low grade insight which can't be used for the inner planets, is expressed like so -

"The proportion existing between the periodic times of any two planets
is exactly the sesquiplicate proportion of the mean distances of the
orbits, or as generally given,the squares of the periodic times are
proportional to the cubes of the mean distances." Kepler

It applies just fine to the time the inner planets take to orbit the Sun. From
the viewpoint of the Earth, maybe the "periodic times" of all the inner planets
are one Earth year, but that's just an illusion.

I shouldn't have to tell you to be Copernican and not geocentric!

John Savard