• Click several combinations of the top six buttons to see how they control the animation.
• Click and drag the yellow triangle (time slider) to display conditions at different times.
• If you need definitions for any of the labels that appear in the animation, enter the words in an Internet search engine.

1. Eccentricity
• Select Top View and Orbit.
• From Orbital Parameters, click Eccentricity (only).
• Drag the time slider up and down to see the shape of Earth's orbit at different times. Eccentricity is a measure of how circular an orbit is
• The magenta line in the graph shows how global temperature would change if eccentricity were the only orbital parameter that changed.
2. Precession
   • Select Oblique View, Rotation, and Orbit.
   • From Orbital Parameters, click Precession (only).
   • Drag the yellow slider up and down fairly slowly to see the motion of precession. Have you seen that motion before? Some people recognize it as the wobble of a spinning top.
   • To see the effect precession has on Earth, go to Top View, set the animation to your favorite season, click season lock, and move the time slider up and down again.
   • The result of precession is that solstices and equinoxes occur at different locations in the orbit, and this changes the season that is occurring when Earth is closest to and farthest from to the Sun.
   • The magenta line shows how global temperature would change over time if precession were the only orbital parameter that changed.
3. Tilt
   • Select Oblique View. Use Faster Orbit to move Earth directly to the right or left of the Sun, then click Orbit.
   • From Orbital Parameters, click Tilt (only).
   • Drag the time slider up and down to see how the angle Earth's axis makes with its orbital plane changes over time.
   • The magenta line shows how global temperature would change over time if the tilt of Earth's axis were the only orbital parameter that changed.

• Click Vostok Ice Core.
• The green line in the graph shows scientific estimates of global temperature for the last 400,000 years. Temperatures are based on the ratio of light and heavy oxygen atoms in layers of ice in a core drilled from Vostok Station in Antarctica.
• Click various combinations of Eccentricity, Precession, and Tilt to see how global temperature is affected by these orbital parameters.
• Which combination of orbital parameters do you think produces the best match with temperatures derived from the Vostok Ice Core?
• If global temperature were only controlled by orbital parameters, how would you expect global temperature to change in the future?

Orbital information obtained from various sources.

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