what is a planets backward motion in the sky called
Apparent retrograde motion
title: Apparent retrograde motion text: verb meaning to become, to appear, to behave—or appear to move—in a retrograde fashion. Although planets can sometimes be mistaken for stars as one observes the night sky, the planets actually change position from night to night in relation to the stars. Retrograde (backward) and prograde (forward) are observed as though the stars revolve around the Earth. Ancient Greek astronomer Ptolemy in 150 AD believed that the Earth was the center of the Solar System and therefore used the terms "retrograde" and "prograde" to describe the movement of the planets in relation to the stars. Although it is known today title: Apparent retrograde motion text: Apparent retrograde motion Apparent retrograde motion is the apparent motion of a planet in a direction opposite to that of other bodies within its system, as observed from a particular vantage point. Direct motion or prograde motion is motion in the same direction as other bodies. While the terms "direct" and "prograde" are equivalent in this context, the former is the traditional term in astronomy. The earliest recorded use of "prograde" was in the early 18th century, although the term is now less common. The term "retrograde" is from the Latin word "retrogradus" – "backward-step", the affix "retro-" meaning "backwards" title: Apparent retrograde motion text: and "gradus" "step". "Retrograde" is most commonly an adjective used to describe the path of a planet as it travels through the night sky, with respect to the zodiac, stars, and other bodies of the celestial canopy. In this context, the term refers to planets, as they appear from Earth, to stop briefly and reverse direction at certain times though in reality, of course, we now understand that they perpetually orbit in the same uniform direction. "Mercury in retrograde" is an example of the term used as a noun for retrograde "motion". "Retrograde" is also sometimes used as an intransitive title: Astrological transit text: apparent backward motion through the sky caused by the Earth travelling past a slower-moving outer planet, or when the Earth is itself passed by a faster-moving inner planet. The outer planets are retrograde for over 40% of the time. In astrology, this backward movement was traditionally thought to be unlucky or inauspicious, as it went against the 'natural' order of movement (or 'direct movement' as it is known). Most modern astrologers consider the retrograde movement of a planet to be malefic, indicative of stress or difficulty. For example, the retrograde movement of Mercury is commonly thought to signify difficulties in title: Apparent retrograde motion text: switch direction as they cross Earth's sky. Though all stars and planets appear to move from east to west on a nightly basis in response to the rotation of Earth, the outer planets generally drift slowly eastward relative to the stars. Asteroids and Kuiper Belt objects (including Pluto) exhibit apparent retrogradation. This motion is normal for the planets, and so is considered direct motion. However, since Earth completes its orbit in a shorter period of time than the planets outside its orbit, it periodically overtakes them, like a faster car on a multi-lane highway. When this occurs, the planet being