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Science Class lesson About 9 minutes

Seasons and Earth's Tilt

    Why Earth has seasons

    Earth has seasons because Earth's axis tilts 23.5 degrees.

    23.5° Straight up North Pole Northern Hemisphere Equator Southern Hemisphere Axis
    Axis: an imaginary line through Earth from the North Pole to the South Pole. Earth spins around the axis.

    Watch Earth go around the Sun

    Sun Northern Hemisphere The 4 axis lines are parallel.
    Orbit: the path of Earth around the Sun. Earth's orbit is almost a circle. Northern Hemisphere: the half of Earth north of the equator.

    CAUTION: Do not say that the distance from the Sun causes seasons. Use the tilt of Earth's axis to explain seasons.

    Fact: Earth is closest to the Sun in early January. The Northern Hemisphere has winter in January.

    Try it

    Move Earth through 1 year

    1. Move the slider to pick a date.
    2. Or drag Earth around the orbit.
    3. Pick a hemisphere.
    4. Compare the Sun angle, the daylight, and the distance.
    Season
    Noon Sun angle
    Daylight
    Distance from the SunSame for both hemispheres

    The sunlight panel shows noon at a place 40 degrees from the equator.

    Quick check

    Answer 5 questions. You see your score at the end.