Skip to main content
Physics LibreTexts

9: Orbital Dynamics- Planets and Moons in Motion

  1. Last updated
  2. Save as PDF
  • Page ID
    25250

    • \( \newcommand{\vecs}[1]{\overset { \scriptstyle \rightharpoonup} {\mathbf{#1}} } \) \( \newcommand{\vecd}[1]{\overset{-\!-\!\rightharpoonup}{\vphantom{a}\smash {#1}}} \)\(\newcommand{\id}{\mathrm{id}}\) \( \newcommand{\Span}{\mathrm{span}}\) \( \newcommand{\kernel}{\mathrm{null}\,}\) \( \newcommand{\range}{\mathrm{range}\,}\) \( \newcommand{\RealPart}{\mathrm{Re}}\) \( \newcommand{\ImaginaryPart}{\mathrm{Im}}\) \( \newcommand{\Argument}{\mathrm{Arg}}\) \( \newcommand{\norm}[1]{\| #1 \|}\) \( \newcommand{\inner}[2]{\langle #1, #2 \rangle}\) \( \newcommand{\Span}{\mathrm{span}}\) \(\newcommand{\id}{\mathrm{id}}\) \( \newcommand{\Span}{\mathrm{span}}\) \( \newcommand{\kernel}{\mathrm{null}\,}\) \( \newcommand{\range}{\mathrm{range}\,}\) \( \newcommand{\RealPart}{\mathrm{Re}}\) \( \newcommand{\ImaginaryPart}{\mathrm{Im}}\) \( \newcommand{\Argument}{\mathrm{Arg}}\) \( \newcommand{\norm}[1]{\| #1 \|}\) \( \newcommand{\inner}[2]{\langle #1, #2 \rangle}\) \( \newcommand{\Span}{\mathrm{span}}\)\(\newcommand{\AA}{\unicode[.8,0]{x212B}}\)

    It is perhaps odd, but quite true that when you ask most people to picture a planet, a moon, or the entire solar system, they tend to visualize a series of bodies frozen in place in a neat line as you might see on a classroom poster or a textbook illustration. Almost no one pictures moons and planets racing around in orbit, moving like horses careening around a track.

    Even so, motion is one of the most fundamental qualities of our successful models of the solar system. Motion involves distance, time, velocity, and acceleration; it may be linear, circular, or even elliptical in nature. We’re going to skirt around all the math and physics that are implied in this and focus on one thing – movement! Our goal will be to get your students to incorporate movement into their fundamental mental picture of the solar system.

    • 9.1: A Working Model of the Lunar Phases
      The lunar phases are obviously a play of sunlight and shadow, so we will include the light from the Sun in our new model as well. It might seem at first glance that adding shape, motion, and the effects of a distant light source into our model would make it far too complex to understand easily – not so! The power of a good scientific model to explain and simplify is often greatly underestimated – as your students will soon show you!
    • 9.2: Aristotle’s Flat Moon
      The most common misconception among adults about the lunar phases is that they believe that the Earth’s shadow falling on the Moon somehow causes or creates the lunar phases! Maybe that Aristotle fellow wasn’t as silly as he appears at first glance! In any case, let’s test Aristotle’s theory as Galileo did and see what happens.

    This page titled 9: Orbital Dynamics- Planets and Moons in Motion is shared under a CC BY-NC-SA 4.0 license and was authored, remixed, and/or curated by Daniel E. Barth via source content that was edited to the style and standards of the LibreTexts platform; a detailed edit history is available upon request.