Aphelion and Perihelion, Apogee and Perigee

Aphelion and Perihelion

The terms Aphelion and Perihelion are used to refer to the furthest and closest points respectively, in a planet’s orbit around the Sun.
The term Aphelion is derived from the Greek words ‘apo-‘ meaning away and ‘Helios’ meaning Sun. It denotes the point in an orbit where the celestial body is furthest from the Sun.
Conversely, Perihelion comes from the Greek ‘peri-‘ meaning near, and ‘Helios’ meaning Sun. It denotes the point in an orbit where the celestial body is nearest to the Sun.
The speed of planetary motion is not constant, but varies dependent on the distance from the Sun. The planet moves slower at its Aphelion and faster at its Perihelion.
Aphelion and Perihelion do not only refer to Earth’s orbit, but can be applied to any celestial body orbiting the Sun.

The terms Apogee and Perigee refer to similar concepts as Aphelion and Perihelion, but related to an object’s orbit around the Earth rather than the Sun.
Apogee is the point in an orbit around the Earth where the celestial body is furthest from the Earth. It comes from the Greek words ‘apo-‘ meaning away, and ‘ge’ meaning Earth.
Perigee is the point where the celestial body is closest to Earth. The term stems from ‘peri-‘ meaning near, and ‘ge’ meaning Earth.
Similar to planetary motion around the Sun, the speed of motion is not constant when an object is orbiting Earth. The object moves slower at its Apogee and faster at its Perigee.
Apogee and Perigee are terms specifically used for objects orbiting Earth, such as the Moon or artificial satellites.

Aphelion and Perihelion refer to the furthest and closest points in a planet’s orbit around the Sun, respectively.
The speed of a celestial body varies in its orbit, moving slower at Aphelion and faster at Perihelion.
Apogee and Perigee are equivalent terms to Aphelion and Perihelion but relate to an object’s orbit around the Earth.
An object in Earth’s orbit moves slower at its Apogee and faster at its Perigee.
The terms are applicable universally and can describe the orbit of any celestial body around the Sun (Aphelion and Perihelion) or the Earth (Apogee and Perigee).