eption for the first time of Kepler's Laws, and
shall see that the first of Kepler's Laws is solved simply by giving an
orbital velocity to any central body, the result of which will be that
the circular form of any planet's orbit will be changed from the
circular into one of elliptic form.

Let me ask the reader to perform a very simple experiment to confirm
this fact. Take a piece of string and a lead pencil, and start to draw a
circle on a piece of paper (Fig. 24). When, however, one quarter of the
circle has been drawn, viz. _D_ _F_, move the end of the piece of string
representing the centre of the circle along the paper, as represented in
the diagram, from _A_ to _B_. The result will be that the pencil will
now travel parallel with the moving centre for a time from _F_ to _G_,
and then, when the centre is brought to rest again, the other part of
the half ellipse _G_ _H_ may be completed. In the same way, by reversing
the motion, the other half of the ellipse may be completed. So that it
is possible for an ellipse to be formed simply by moving the central
point of a circle, and the motion of that central point will change the
form of a circle into an ellipse. It is something like this that takes
place in the planetary world, with this difference, that the central
point which represents the sun does not return from one focus to
another, but continues to journey on through space, with the result that
the orbit of any planet is not strictly an ellipse, as we shall see
later on. We have, then, the sun occupying the centre of the solar
system, with all the planets revolving round it. We will take the sun
and the Earth as examples. Let _S_ in the diagram represent the sun, and
_E_ the Earth at its mean distance of 92,000,000 miles away (Fig. 25).

[Illustration: Fig: 25.]

The Earth we know is moving with a velocity of about 64,800 miles per
hour around the sun, or an average velocity of 18 miles per second, so
that while the Earth is moving 64,800 miles through space to perform the
half-circle, _E_ _D_ _C_, the sun is also travelling 18,000 miles
towards the point _D_.

What, therefore, is the effect of this onward movement of the sun
towards the Earth as it tries to complete the half-circle _E_ _D_ _C_?
We have seen that the centrifugal force due to the pressure of the
electro-magnetic Aether waves is exactly equal to the centripetal force
exerted by the sun on any planet, and if that be so, it can be readily
seen