Re: inertial forces (definition)

[brian whatcott <inet@INTELLISYS.NET>]

At 20:18 10/19/99 -0400, Bob Sciamanda wrote:
> Proposition VII, Theorem VII of Isaac's Principia is entitled:
> "That there is a power of gravity tending to all bodies, proportional to
> the several quantities of matter which they contain"
>
> He thus perceived both the "force of inactivity" (below) and the force of
> gravitation to be each proportional to the same property of an object: the
> "quantity of matter".  I don't think he saw anything striking in this; he
> knew of no other force laws with which to see a contrast....

> Bob Sciamanda

I am not quite sure of the sense in which Newton may be said to be
unaware of other force laws: in the lines immediately preceding
those you quote above, Newton remarks,
" The power of gravity is of a different nature from the power of
 magnetism; for the magnetic attraction is not
as the matter attracted..." [i.e proportional to mass]

Elswhere he mentions an inverse square law of magnetism
(though here he suggests it may diminish as much as by an
inverse cube of distance "by rude observations")

brian whatcott <inet@intellisys.net>
Altus OK