Hobbies And Interests
Things You'll Need
Instructions
Draw a diagram of the moon orbiting the earth. Do this by drawing one circle that represents the earth, a larger circle around the earth that represents the moon's orbit and then a smaller circle on the orbital path that represents the moon.
Draw a straight line from the center of the earth to the center of the moon in your diagram.
Consider the time for which you wish to calculate the moon's displacement along its trajectory. For instance, you might want to calculate how far the moon will travel on its orbit in one week, or seven days.
Divide the number of days you are calculating by 27.3--the period of time it takes the moon to complete a revolution.
Example: 7/27.3 = 0.256
Multiply your previous result by 360 degrees--the angular distance of a complete orbit.
Example = 0.256 x 360 degrees = 92 degrees
This calculation tells you that in seven days, the moon will travel through 92 degrees of its orbit.
Put the straight edge of your protractor along the line in your diagram that connects the moon to the earth. Align the center of the straight edge with the center of the earth.
Find the 92 degree measurement on your protractor and make a mark at that point on the circle representing your moon's orbit. Note that it does not matter whether you choose a clockwise or counter-clockwise direction for your angle, because that would vary depending on your vantage point looking at the moon's orbit from space.
Draw another moon at that 92 degree mark on your diagram and connect it to the earth with a straight line. By comparing the two moons in your diagram, you can now see the moon's displacement through its trajectory over seven days.