Reference no: EM133417971

Question: Let's try to understand this odd retrograde motion by seeing what's happening from high above the Solar System. Make sure the Ground and Atmosphere are off. Use the Search Window to find and center Solar System Observer. Then press CTRL-G to go there. Then Find and center the Sun. Open the View window (use the menu or press F4) and, in the Sky sub-menu, put check marks next to Show Solar System Objects, Show Planet Markers and Show Planet Orbits. Also put a check in the box next to Labels and Markers and drag the slider next to it all the way to the right. Close the View window.

Change the Date & Time back to October 1, 2007 (the time doesn't matter). Now zoom in or out until the orbit of Mars just fills the screen. The Field Of View (FOV) should be roughly about 0.4°.

You are looking down at the orbits of most of the Solar System on October 1, 2007 - the same day you started looking at Mars for the previous section. The positions of Mercury, Venus, Earth and Mars are labeled.

Tape a blank piece of thin tracing paper over your computer screen. Hold a ruler up to the screen and use it to gently draw a straight line from Earth, through Mars and down to the edge of the screen. Make sure the ruler extends all the way to the edge of the paper. Label this line with the date (10/1).

Press the "]" (right square bracket) button to let one week pass. The right square bracket button should be two keys to the right of the letter P on your keyboard. Use the ruler again to make to make a second line from Earth to Mars and down to the edge of the screen. Label this one with new date (10/7). Press the right square bracket button again to let another week pass and repeat the procedure. Continue making lines on the paper once a week until February 21, 2008.

When you are done, examine the lines you printed on the paper, with the dates marked. Remember, the spot where each line hits the edge of the paper indicates where Mars would appear that day against the distant stars from our point of view here on Earth. Call that spot "Mars' apparent position." Look at the spot carefully from day to day to determine how it moves from our point of view here on Earth. Compare the pattern of dots to the dates when Retrograde Motion began and ended, that you measured earlier. This should help you understand why retrograde motion occurs.