How is Sunlight Changing? Mornings in North America (Back to 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 continues to get shorter as the sun appears higher in the sky. (The rays begin to the Earth more directly.) If your students are tracking sunrise and sunset times, they may have noticed these things this month: The sun continues to make a comeback! We've just passed the spring equinox (March 20), and daylength is changing more quickly. Remember that we also moved our clocks ahead an hour for Daylight Savings Time. So to compare apples to apples in our images from space, we use universal time (UTC), which does not change. Click for larger image. On the spring equinox, the length of the day and night were about 12 hours. This was true everywhere on Earth. (The word equinox means "equal nights.") On the equinox, the sun's strongest rays are directly hitting the equator. The Earth's axis is not tipped toward or away from the sun. As we move closer to the summer solstice, students should notice that days continue to get longer and warmer. Why? The strongest rays of the sun begin to hit north of the equator. Why does all this matter? All seasonal changes – temperature, plant growth and life cycles, animal migrations, and so on – are driven by changes in the amount of available sunlight (called daylength or photoperiod) and its intensity (related to the angle at which it strikes the Earth). This Season Teachers Kids Orientation Registration Search Copyright 1997-2009 Journey North. All Rights Reserved. Questions or comments? Contact us.