From the properties of the ellipse, A is the pericentre or nearest point of the orbit to the centre of attraction and B the **apocentre** or most distant point.

To do this the actual speed in the orbit, and in a yet higher degree the angular speed around F, must be greatest at pericentre, and continually diminish till the **apocentre** is reached.

From the law of angular motion of the latter its radius vector will run ahead of PQ near A, PQ will overtake and pass it at **apocentre**, and the two will again coincide at pericentre when the revolution is completed.

It arises from the ellipticity of the orbit, is zero at pericentre and **apocentre**, and reaches its greatest amount nearly midway between these points.