Page:A short history of astronomy(1898).djvu/166

120 from the sun), the motion of the earth itself being directly to or from Jupiter produces no effect on the apparent motion of Jupiter (since any displacement directly to or from the observer makes no difference in the object's place on the celestial sphere); but Jupiter itself is actually moving towards the left, and therefore the motion of

Jupiter appears to be also from right to left, or from west to east. Hence, as before, between 1 and and between  and 2 there must be points j1, j2 (Jan. 24 and May 27, in fig. 6) at which Jupiter appears for the moment to be stationary.

The actual discussion of the stationary points given by Coppernicus is a good deal more elaborate and more technical than the outline given here, as he not only shews