Concept

Nadir

The point directly below your feet.

The point on the celestial sphere directly beneath the observer, opposite the zenith.

Overview

The point on the celestial sphere directly beneath the observer, opposite the zenith.

See also

Zenith

The point directly overhead.

Perihelion

The closest point in an orbit to the Sun.

Aphelion

The farthest point in an orbit from the Sun.

Perigee

The closest point in an Earth-centred orbit.

Apogee

The farthest point in an Earth-centred orbit.

Event Horizon

The point of no return around a black hole.