1. The 4 Seasons Many of the graphics came from Gary Becker in Allentown, PA

2. What causes the seasons on Planet Earth? Winter – Spring – Summer – Fall – What causes the seasons on Planet Earth? Winter – Spring – Summer – Fall – Galileos image of the Earth and Moon

3. Are the Seasons caused by the Earths orbit? Maybe the Earth is closer to the sun in the summer, and farther away in the winter??? Maybe the Earth is closer to the sun in the summer, and farther away in the winter??? Well, its true if you live in Chile, Argentina, Australia and other places in the southern hemisphere… Well, its true if you live in Chile, Argentina, Australia and other places in the southern hemisphere…

5. June/July December / January March September

6. So the Earth is actually closer to the sun in December/January. This makes the southern hemispheres summer potentially hotter than the northern hemispheres. So the Earth is actually closer to the sun in December/January. This makes the southern hemispheres summer potentially hotter than the northern hemispheres. Of course, overall climate and other factors affect the real winter weather. Of course, overall climate and other factors affect the real winter weather.

7. The Solution!!! The Earth is tilted 23.5° What do you mean tilted – compared to what? OK, compared to the plane it makes in orbit around the sun – it is 23.5 degrees off straight up and down.

8. From a Northern Hemisphere perspective

9. Whats this Northern Hemisphere Perspective all about? Whats this Northern Hemisphere Perspective all about? The seasons are opposite in the Southern Hemisphere – Winter is in June-July-August and Summer is in December-January The seasons are opposite in the Southern Hemisphere – Winter is in June-July-August and Summer is in December-January Look at the image again, and notice the people in the south are opposite Look at the image again, and notice the people in the south are opposite You wont see snow for Christmas in Australia You wont see snow for Christmas in Australia

10. Southern Perspective Winter Summer Vernal Autumnal

11. The Suns motion during a year Northern Hemisphere Northern Hemisphere

14. Hawaii is special Hawaii is special Since Hawaii is just south of the Tropic of Cancer – there are two days in the year when the sun is directly overhead. Since Hawaii is just south of the Tropic of Cancer – there are two days in the year when the sun is directly overhead. In addition, there are a number of weeks when the sun is to the north of us. In addition, there are a number of weeks when the sun is to the north of us. Anyone living in the Tropics (between 23.5° N and 23.5° S) has one or two days with the sun directly overhead. Anyone living in the Tropics (between 23.5° N and 23.5° S) has one or two days with the sun directly overhead.

15. Intensity of Sunlight depends on Angle Warmer Cooler

16. Shadows

17. Latitude, Shadows and Intensity At the Equinox At the Equinox

18. An Example from North America June December South Pole Winter South Pole Summer

20. Special Latitudes North Pole90° N North Pole90° N Arctic Circle66.5° N Arctic Circle66.5° N Tropic of Cancer23.5° N Tropic of Cancer23.5° N Equator 0° Equator 0° Tropic of Capricorn23.5° S Tropic of Capricorn23.5° S Antarctic Circle66.5° S Antarctic Circle66.5° S South Pole90° S South Pole90° S

21. Special Days North PoleMidsummer – June 21 North PoleMidsummer – June 21 Arctic CircleJune 21 Arctic CircleJune 21 Tropic of CancerJune 21 Tropic of CancerJune 21 EquatorMarch 21 & September 21 EquatorMarch 21 & September 21 Tropic of CapricornDecember 21 Tropic of CapricornDecember 21 Antarctic CircleDecember 21 Antarctic CircleDecember 21 South PoleMidsummer – December 21 South PoleMidsummer – December 21 Note – Ive said the 21 st, but there is some variation – sometimes 22 nd or even 23 rd - it has to do with leap years and the fact that a year is actually 365.25 days long

22. The view to the North - Polaris

23. The view to the South – No south polar star

24. Disclaimer Aloha I put together these power points for use in my science classes. You may use them in your classes. Some images are public domain, some are used under the fair-use provisions of the copyright law, some are mine. Copyright is retained by the owners! Ted Brattstrom