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Lesson H


October 2, 2007

The Seasons

Review of the tilt of the earth, rotation and orbit was brainstormed.  Students were provided with information on how the tilt, rotation and orbit of the earth effects the seasons.  Equinox and Solstice were introduced to the students through internet images and information.

Notes taken from : http://www.wxdude.com/basics.html

Student Notes:
The earth is slightly tilted on its axis.  As the sun shines on the earth, it shines more directly on the northern hemisphere in June, and more directly on the southern hemisphere in December.  That's why the seasons are different  in each hemisphere.  In the spring and fall, the sun shines fairly straight on the equator, giving both hemispheres equal warming. 


 
 Spring

The first day of spring is around March 20 or 21, depending on what day the vernal equinox occurs. This is when the sun sits directly above the equator on its apparent trip northward.  Of course this sun isn’t moving; Earth is. As Earth revolves around the sun, the top half, called the Northern Hemisphere, becomes tilted more toward the sun as winter turns to spring. The word “equinox? comes from Latin and means “equal nights.?   Around March 20, sunrise and sunset are about twelve hours apart everywhere on Earth. 

 

Summer

The summer solstice in the Northern Hemisphere, or top half of Earth, is around June 21.  That's when the sun reaches its most northern point over our planet.  The days around June 20 are the longest of the year, and the rays from the sun beat almost directly down on use and warm us up. Solstice: This comes from two words, sol, meaning “sun,? and sistere, meaning “to stand.? It is not the heat but the humidity.  Humidity is the amount of moisture in the air.  When the air has so much moisture in it, our bodies don’t do a good job of cooling us down because sweat doesn’t evaporate as quickly from our skin.  That is why we feel so hot on a humid day. 

 

Autumn

The changes start with the sun and the earth’s orbit around it.  Often people think that our temperatures get cooler in autumn because the earth moves farther from the sun.  But this is not true. What actually changes is not the distance of the earth to the sun, but the angle of the sun’s rays on the earth. With less and less direct sunlight on the top half, the days here get shorter and temperatures get colder as winter nears.  Those shorter days and cooler temperatures act as a signal to the trees and plants around us to get ready for winter.

 

Winter

Winter is when earth’s north pole is tilted farther away from the sun than at any other time of the year.  This is called the winter solstice, and the days just before Christmas are the shortest of all.

Click below to view the video presentation for this lesson.




Resources:
Weather Dude
ESL Seasons Video
Google Earth