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 gets shorter after the winter solstice as the sun appears higher in the sky. (The rays begin to the Earth more directly.) On December 21 (the winter solstice), the Northern Hemisphere had its shortest day of the year. If your students are tracking sunrise and sunset times, they may begin to notice these things: Daylength shortens before the solstice and lengthens after the solstice, but it barely changes for about a week before or after the solstice. (Remember, solstice means sun stop. The apparent movement of the sun is imperceptible during this period.) The sun actually begins to set later a couple of weeks before the winter solstice (depending on your latitude), but the sunrise doesn't begin to get earlier until two weeks after the solstice: about the 5th of January. That's why the morning of January 1 looks darker in the photo than we might expect. (This has to do with the tilt of Earth's axis and its slightly elliptical orbit.) Stay tuned. You'll soon discover that the rate of change in daylength from day to day is lowest near the winter and summer solstices and highest near the spring and fall equinoxes. 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: More: Reasons for Seasons: Teacher Background Information >> Facebook Pinterest Twitter © 1997 – 2019 Journey North. All rights reserved.