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The Reason For the Seasons

The Reason For the Seasons. Vocabulary. Axis of Rotation – an imaginary line running from the north pole to the south pole Revolution – the time it takes to go around something once It takes one day or 24 hours for the earth to revolve on its axis once

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The Reason For the Seasons

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  1. The Reason For the Seasons

  2. Vocabulary Axis of Rotation – an imaginary line running from the north pole to the south pole Revolution – the time it takes to go around something once • It takes one day or 24hours for the earth to revolve on its axis once • It takes one year for the earth to revolve around the sun

  3. Why Do We Have Different Seasons? • The Sun stays in its position at the center of the solar systemand the Earth revolves around the Sun. • Seasons occur because the Earth is tilted on its axis. • If the Earth were not tilted on its axis, we would not have seasons.

  4. Why Do We Have Different Seasons? • The Earth is tilted on a 23.5°angle. • The Earth’s axis at the North Poleis always pointed towards Polaris, also called the North Star.

  5. Why Do We Have Different Seasons? • The tilt causes sunlight to strike the Earth for different lengths of time at different times of the year.

  6. Spring

  7. Spring • The axis is not tilted toward or away from the Sun. • The Sun’s rays are shining directly on the Equator. • Two days per year all places on earth have daylight for equal lengths of time. In the spring, this is called the Spring (Vernal) Equinox, which occurs on March 20th.

  8. Spring

  9. Summer

  10. Summer • The Earth’s axis is tilted toward the Sun. • The Sun’s rays are shining directly on the Tropic of Cancer,23.5° north of the Equator. • In the Northern Hemisphere, the day with the longest photoperiod (amount of sunlight) is called the Summer Solstice, which occurs this year on June 21st.

  11. Summer

  12. Autumn

  13. Autumn • The axis is not tilted toward or away from the Sun. • The Sun’s rays are shining directly on the Equator. • Two days per year all places on earth have daylight for equal lengths of time. In the fall, this is called the Autumnal (Fall) Equinox, which occurs this year on September 22nd.

  14. Autumn

  15. Winter

  16. Winter • The Earth’s axis is tilted away from the Sun. • The Sun’s rays are shining directly on the Tropic of Capricorn, 23.5° south of the Equator. • In the Northern Hemisphere, the day with the shortest photoperiod (amount of sunlight) is called the Winter Solstice, which occurs this year on December 21st.

  17. Winter

  18. Question: • During what season is the Earth closest to the Sun?

  19. Question: • Most people think it is summer because it is hottest in the summer and here in the Northern Hemisphere, we are facing the Sun.

  20. Question: • The Earth is actually closest to the Sun during the Winter!

  21. How Is Longitude Related to the Seasons? Comparing both images, notice how much earlier sunrise occurred in the Southern Hemisphere on the Winter Solstice. This is because the Northern Hemisphere was tilted away from the Sun! On the Spring Equinox, locations at the same longitude experience sunrise at the same time. On the Winter Solstice, locations at the same longitude do not have sunrise at the same time.

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