How is Sunlight Changing? Mornings in North America (Back to Sunlight Observation) Shadows Change, Too! Are your students measuring the length of an object's shadow at the same time each week or month? They should begin to notice that the shadow appears longer each week as the sun appears lower in the sky. (The most direct rays are hitting the Earth at more of an angle.) If your students are tracking sunrise and sunset times, they may have noticed these things: The days are getting shorter here and the nights are getting longer. They should see from the globe images that the Northern Hemisphere experienced more darkness on October 1 than on September 1. Why does all this matter? All seasonal changes – temperature, plant growth and life cycles, animal migrations, and so on – are driven by shifts in the amount of available sunlight (called daylength or photoperiod) and its intensity (related to the angle at which it strikes the Earth). For more information on changing sunlight, go here: Reasons for Seasons: Teacher Background Information >>     Copyright 1997-2011 Journey North. All Rights Reserved. Questions or comments? Contact us.