![]() ![]() Starting tonight, the Red Planet will resume its usual eastward, or. This demonstration can be done without the camera and just with two student volunteers. On Thursday (Jan.12), Mars will end its retrograde motion which has seen it moving westward through the night sky. As the camera person keeps the camera on Mars, it appears to move backwards as its orbit is overtaken. The camera is pushed in a "circular" orbit by an assistant while the Mars apparatus is also pushed in a circular orbit, at a slower speed. Astrology aside, Mars in retrogradewhich only occurs once every two years or sois a great time to view the fourth planet and to appreciate an intriguing aspect of how our solar system works. ![]() ![]() Mars is represented by a styrofoam ball hanging from a stand on wheels. 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. In this demonstration, Earth is represented by a camera on a rolling chair. As Earth (E) passes a superior planet such as Mars (M), the superior planet (M') will temporarily appear to reverse its motion across the sky. A schematic of the motion is shown in Figure 1:įigure 1: Apparent retrograde motion of Mars The apparent retrograde part of Mars's orbit occurs for a few months before it returns to motion in the eastward direction. Jupiter moves across the sky in a very predictable pattern, but every now and then it reverses direction in the sky, making a tiny loop against the background stars this is Jupiter in retrograde. With respect to the background stars, the motion of Mars will then appear to slow down and reverse direction as the Earth comes to the point in its orbit where it is closest to Mars. Just as the movement of Mars appears to change between retrograde and prograde, so does that of Jupiter. Both planets move eastward, but since the Earth moves faster than Mars in its orbit, Mars will be overtaken by the faster-moving Earth. This is known as the retrograde motion of Mars Near the end of January, it reverses direction. 2 Mars was portrayed on the ceiling of the tomb of Seti I, on the Ramesseum ceiling, 3 and in the Senenmut star map. Mars has a larger orbit than Earth, and therefore it moves more slowly in its orbit. Over the next three months, from November to late January, Mars moves toward the west each night. By the 2nd millennium BCE they were familiar with the apparent retrograde motion of the planet, in which it appears to move in the opposite direction across the sky from its normal progression. Note that Earth passes between Mars and the Sun at roughly 780 day intervals this interval is known as the Synodic Period of Mars. Mars actually doesn't change its motion at all - retrograde motion is an illusion caused by Earth's motion. The most common example of retrograde motion within the solar system is the apparent westward motion of Mars. Retrograde motion occurs while Earth passes between Mars and the Sun moving faster than Mars. When an object in the sky appears to move backwards with respect to the common motion of the system, it is said to be in retrograde motion. ![]()
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