PART III: THE RELATIVE MOTIONS OF THE PLANETS
This part of the lab will allow you to examine the location of the planets relative to echother as well as the Sun and the background sky. You will see a display that shows the location of the Sun, the Earth and the planets under study. In this model we are only dealing with the visible planets (Mercury, Venus, Mars, Jupiter and Saturn). The outer circle indicates the constellations. You can use the buttons to move the model forwards and backwards in time.
The constellations are far enough away that they appear stationary as the planets move in their orbits. By changing your point of view above, you can be an observer on any of the planets or the sun. When you are identifying the constellation a planet will be seen in, be sure to center the display on the location of the observer (usually the Earth).
The elongation angle of a planet is the difference between its heliocentric (relative to the Sun) and geocentric (relative to the Earth) longitudes. The applet will give you the longitude for any of the bodies above. Set your point of view to the body you want to observe from (usually the Earth or the Sun), and check off the Show Longitude box for the planet you're interested in. The longitude will appear in the text box to the right.
Notice that 0 degrees longitude is horizontal and toward the right side of the screen.
Answer questions 3.1 - 3.18 on the worksheet.
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