Unit 1: The Precession of the Earth


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  • Figure 1
    precess.gif - 2.1 K
    In our discussion of the seasons, it was assumed that the orientation of the Earth's axis remained constant. We assumed that the northern axis of rotation was pointing toward Polaris (def.). In fact, the Earth's axis is "wobbling", meaning that the axis changes its orientation with respect to celestial objects (figure 1). This wobbling motion is referred to as "precession". Precessions is similar to the wobbling motion of a top as it spins.

    Proof:You are not responsible for this proof.

    Period: 26,000 years

    Observed Effects:

    Self-check Questions:

    1. In 13,000 years, what season will people living in the southern hemisphere experience on June 21? (ans.)
    2. In 13,000 years, what season will people living in the southern hemisphere experience on March 21? The people living in the northern hemisphere? (ans.)

    Homework Questions: (To submit your answers to the homework questions, first copy the questions from this page and paste them into the homework form. Insert your answers below the questions. Fill in the remaining form elements and submit. Your homework will be e-mailed to me. I will return your graded homework to you in the private e-mail of the comm center).

    1. If the Earth were untilted, would we experience precession of the Seasons? Explain (1 point)

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