The Earth's axis is tilted 23.5 degrees in relationship to its orbit around the Sun, causing the different seasons in temperate climates. During summer in the Northern hemisphere the tilt is toward the Sun, causing a more direct striking of the Sun's rays. Just the opposite happens in the Southern hemisphere, they have winter while the Northerners are in summer. Although the tilt remains at 23.5 degrees, it tends to wobble as the years go by. What we mean by this is that the gravitational pull of the Moon and Sun causes Earth's axis to slowly move through the sky in a motion similar to a gyroscope. One complete wobble takes 26,000 years to complete in which time different stars take over the title of "North Star".

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