Earth's Orbit and Seasons

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orbit

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Path Earth follows as it revolves around the sun. Earth's orbit around the sun is a slightly elongated circle.

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revolution of Earth

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Earth revolves around the sun in its orbit. Takes 365 1/4 days for Earth to make 1 full revolution around the sun. 1 revolution = 1 year.

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rotation of Earth

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Turning/spinning of Earth on its axis. Takes 24 hours to complete 1 full rotation. 1 rotation = 1 day.

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solstice

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When the sun reaches its greatest distance, North or South of the equator. Occurs twice a year.

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summer solstice

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When the sun is the farthest north of the equator. 1st day of summer in Northern Hemisphere. Occurs around June 21st. The longest day of the year in Northern Hemisphere (most hours of sunlight).

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autumnal equinox

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When neither Hemisphere is tilted toward or away from the sun. Occurs around September 22nd. 1st day of fall in Northern Hemisphere.

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axis

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Imaginary line through Earth's center from North Pole to South Pole. Earth spins on this axis. Tilted at a 23.5 degree angle.

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cause of seasons

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Tilt of Earth's axis and revolution around the sun. Least drastic at equator because the sun's rays hit this area at about the same angle all year.

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equinox

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Equal day and night everywhere on Earth, 12 hours of sunlight (day) and 12 hours of darkness (night). Occurs when the noon sun is directly over the equator. 2 equinoxes each year.

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leap year

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Occurs every 4 years. 1 extra day is added to February every 4 years to even out the calendar since it takes 365 1/4 days to make a complete revolution around the sun (4 1/4's = 1).