# Intro - NASA and the Layman # Apogee and Perigee Some things are harder to grasp than others, one topic being celestial coordinates. While our minds are attuned to thinking on two-dimensional pieces of paper, three-dimensional thought is often another question, with many textbooks even leaving out knowledge of Strictly speaking, the aphelion refers to the region of an orbit where the body is furthest away from the centre of mass. Now that we've brushed the 'layman' out of the way, let's go look at some of the maths - starting