January threw February
An example of retrograde motion is when Mars appears to temporarily move backward in its orbit as seen from Earth. This is an optical illusion caused by the difference in speeds between Earth and Mars as they revolve around the Sun.
From an observer on Earth, Mars appears to move eastward against the background stars during January through August. This apparent motion is due to both Mars orbiting the Sun and Earth's own orbit around the Sun. However, Mars may also exhibit retrograde motion for a period, where it appears to move westward against the stars, particularly when Earth overtakes it in their respective orbits. Overall, the general trend is eastward, with brief periods of retrograde motion.
The retrograde motion of the planets is well modelled by both the Ptolemaic system and the Copernican system, and by the other models. But the Copernican system explains it more simply because, for example, Mars's retrograde motion is caused simply when Mars is overtaken by the Earth, which goes more quickly round the Sun. Thus an observer on the Earth sees Mars appearing to go 'backwards' on the ecliptic around the time of closest approach (opposition). This can be easily demonstrated by assuming simple circular orbits.
Phobos, one of Mars' moons, orbits in a prograde motion around Mars, meaning it follows the same direction as the planet's rotation.
because Earth, Mars, and the other planets all orbit around the Sun in roughly the same plane. As Earth moves faster in its orbit, it overtakes Mars, causing Mars to appear to move backwards relative to the fixed stars in the sky, creating the illusion of retrograde motion.
When Mars is in retrograde motion, it does not affect its brightness. Mars will continue to appear at its usual brightness in the night sky regardless of its retrograde motion. Retrograde motion refers to how the planet appears to move in the sky, not its actual brightness.
Retrograde
The motion in which Mars appears to reverse its normal direction of motion in the sky is called retrograde motion. This phenomenon occurs when Earth, which moves faster in its orbit, overtakes Mars and creates the illusion that Mars is moving backwards in the sky for a brief period of time.
The heliocentric model explains the retrograde motion of Mars as an optical illusion caused by the relative speeds and orbits of Earth and Mars around the Sun. When Earth overtakes Mars in its orbit, Mars appears to move backward in the sky before resuming its normal forward motion.
Earths faster motion makes Mars appear to be going backwards, the backwards motion, in fact, is what caused retrograde motion. --Ptloemy used Epicycles to explain how geocentrical models worked.
An example of retrograde motion is when Mars appears to temporarily move backward in its orbit as seen from Earth. This is an optical illusion caused by the difference in speeds between Earth and Mars as they revolve around the Sun.
From an observer on Earth, Mars appears to move eastward against the background stars during January through August. This apparent motion is due to both Mars orbiting the Sun and Earth's own orbit around the Sun. However, Mars may also exhibit retrograde motion for a period, where it appears to move westward against the stars, particularly when Earth overtakes it in their respective orbits. Overall, the general trend is eastward, with brief periods of retrograde motion.
From the Earth, the planet Mars appears to backtrack across the sky, against the background stars, over several nights (10 weeks or so) before resuming its normal direction. This apparent retrograde motion is caused by the positioning of the planets Mars and Earth, as Earth passes by Mars (travelling more quickly than Mars due to its closer proximity to the sun). Mars does not actually back track, its orbit remains constant and in the same direction, as with the earth. It only appears to backtrack from observations on Earth as the point of view changes.
Mars experiences an elliptical orbit around the Sun, causing it to move at varying speeds throughout the year. From January through August, Mars moves in its orbit, gradually changing its position relative to Earth and the rest of the solar system. During this time, its apparent motion in the night sky may appear to be retrograde (moving backward) for a period due to the differing speeds and distances between Mars and Earth.
The retrograde motion of the planets is well modelled by both the Ptolemaic system and the Copernican system, and by the other models. But the Copernican system explains it more simply because, for example, Mars's retrograde motion is caused simply when Mars is overtaken by the Earth, which goes more quickly round the Sun. Thus an observer on the Earth sees Mars appearing to go 'backwards' on the ecliptic around the time of closest approach (opposition). This can be easily demonstrated by assuming simple circular orbits.
Phobos, one of Mars' moons, orbits in a prograde motion around Mars, meaning it follows the same direction as the planet's rotation.
because Earth, Mars, and the other planets all orbit around the Sun in roughly the same plane. As Earth moves faster in its orbit, it overtakes Mars, causing Mars to appear to move backwards relative to the fixed stars in the sky, creating the illusion of retrograde motion.