1. “Tilt” of the Earth “How inappropriate to call this planet Earth, when it is clearly Ocean.” Arthur C. Clarke Earth….spit and sand. Maya Angelou

2. The axis of rotation (spin) is contained within the body. The Earth axis runs roughly through the poles. The axis of revolution (orbit) is contained outside the body. These axes are imaginary. The Earth and the sun are not to scale.

3. Since these axes only exist in our minds’ space, mentally we can transport the sun’s axis of orbit over to our planet. 90° away from our axis of orbit is the orbital plane of our planet. This is known as the ecliptic. This is also the path where the sun can be found on our star charts.

4. Celestial equator Axis of orbit Celestial poles Solstice Sun Ecliptic The Solstices are defined by the sun being above or below the celestial equator by an angle of 23°. Ninety degrees from the celestial equator are the celestial poles.

5. Celestial equator Axis of orbit Ecliptic The north celestial pole is found near Polaris, the North Star. This celestial axis is the axis of our rotation (spin). North celestial pole South celestial pole

6. Astronomically the “tilt” of the earth is now defined as the axis of spin (rotation) inclined at an angle of 23 ½ ° to the axis of orbit (revolution). Calculating the angles reveals this relationship. The axis of spin (rotation) is inclined at an angle of 23 ½ ° to the axis of orbit.

7. Credits Intellectual property and scientific knowledge – Larry Mascotti Intellectual property and scientific knowledge – Larry Mascotti Visualizations and presentation development – Bob Snyder Visualizations and presentation development – Bob Snyder