Now such a constellation as the following must sometimes exist: the earth is in perihelion; the line of nodes coincides with the line of apsides and both lie in the line joining earth and sun.
The line of nodes rotates in a period of 18.612 years and the line of apsides in a period of 8.84 years.
Tisserand in 1895.1 It involved the action of no third mass, but depended solely upon the progression of the line of apsides in a moderately elliptical orbit due to the spheroidal shape of the globes traversing it.
They are called the lower or nearer, and the higher or more distant apsides respectively.
The "line of apsides" is that which joins them, forming the major axis of the orbit.
How would you define apsides? Add your definition here.