Dne 22/01/2018 v 02:22 Peter Riedt napsal(a):


The signficance of me Fc comparing to Fg is that Huygens in 1659
was able to already calculate the gravitationl force without knowing G or M.

He did not need to need G nor M.
It was enough to know their product G.M.

For the centripetal formula and ellipses near to circle,
he can approximate an ellipse as a circle,
setting the radius as the mean distance to Sun,
speed as the mean speed to keep the period,
and than to calculate the centripetal force
as the mean gravitational force.

But it is all just an approximation.

Exact calculation for ellipses by centripetal formula
is possible indirectly, but is MUCH more complex
than a simple calculation from the inverse square law.

BTW, according to Huygens centripetal force formula,
if trajectory is straight, the force is zero,
what is not true.

--
Poutnik ( The Pilgrim, Der Wanderer )

A wise man guards words he says,
as they say about him more,
than he says about the subject.