Why do we have seasons?

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Across
  1. 3. The Earth does what about its axis?
  2. 5. There are 365.25 days in what?
  3. 6. When a given amount of heat shines on a bigger surface, each point on the surface receives a lower ______ of heat.
  4. 8. The are four of them on Earth
  5. 11. It's warm all year round at the _________
  6. 12. An imaginary line that extends from the North to the South Pole.
  7. 13. The shape of a planetary orbit
  8. 15. The approximate shape of the Earth is a _______
Down
  1. 1. In which seasons are the days the shortest?
  2. 2. Half of the globe
  3. 4. The source of all energy on Earth
  4. 7. The winter ______ is the shortest day of the year.
  5. 9. The two days in the year when day and night are the same length.
  6. 10. Where the Sun rises
  7. 14. The 21st June is the _________ solstice and the longest day.