An introduction to mathematics, by A. N. Whitehead.

DYNAMICS 45
at the same rate and in the same direction
there is no need to invoke the aid of any
forces.
The difference between the two points of
view is well seen by reference to the theory
of the motion of the planets. Copernicus, a
Pole, born at Thorn in West Prussia (born
1473, died 1543), showed how much simpler
Force (onfalse hypothesis)
Sun
Fig. 4.
it was to conceive the planets, including the
earth, as revolving round the sun in orbits
which are nearly circular; and later, Kepler,
a German mathematician, in the year 1609
proved that, in fact, the orbits are practically
ellipses, that is, a special sort of oval curves
which we will consider later in more detail.
Immediately the question arose as to what
are the forces which preserve the planets in
this motion. According to the old false view,