Seasons
In many parts of the world, the year is made up of four seasons: Winter, Spring, Summer and Fall. We have seasons because the tilt of the Earth's axis causes different parts of the Earth to be struck more directly by the Sun's rays at different times of the year. There is a common misconception that seasons are caused by how close the Earth is to the Sun during different times of the year. The belief is that the closer we are to the Sun, the warmer the temperature would be on Earth. This is not only false, but actually, the reverse is true. During the Winter months in the Northern hemisphere, the Earth is the closest to the Sun, and during the Summer months, the Earth is actually further away. As Earth revolves around the Sun, its axis is always tilted in the same direction, but as Earth travels around the Sun, the part of the Earth tilted towards the Sun changes.
Students know that the weather changes depending upon the time of year, but they lack the understanding of how and why that happens. This Unit will allow them to explore Earth revolving and rotating around the Sun to produce the seasons that they are familiar with.
For part of the year, the north end of the axis slants toward the Sun. During another part of the year, the North Pole slants away from the Sun. When the North Pole is tilted towards the Sun, the Sun's rays strike that part of the Earth more directly. This is when Summer occurs in the Northern hemisphere. The Sun crosses high in the sky during the day and it stays up for a long time. This gives us longer days and shorter nights. When the North Pole is tilted away from the Sun, the Sun's rays strike that part of the Earth less directly. This is when Winter occurs. The Sun remains low in the sky and gives us less warmth.
The solstices are days when the Sun reaches its farthest northern or southern heights in the sky. The Winter solstice occurs on December 21 st or 22 nd and marks the beginning of Winter (this is the shortest day of the year). The Summer solstice occurs on June 21 st and marks the beginning of Summer (this is the longest day of the year). Equinoxes are days in which day and night are of equal duration. The two yearly equinoxes occur when the Sun crosses the celestial equator. The vernal equinox occurs in late March (this is the beginning of Spring in the Northern Hemisphere and the beginning of Fall in the Southern Hemisphere); the autumnal equinox occurs in late September (this is the beginning of Fall in the Northern Hemisphere and the beginning of Spring in the Southern Hemisphere). (http://www.enchantedlearning.com/subjects/astronomy/planets/Earth/Seasons.shtml) During the Winter solstice, the Sun does not rise north of the Artic Circle, sits directly above the tropic of Capricorn and does not set south of the Antarctic Circle. During the Summer solstice, the Sun does not set north of the Artic Circle, sits directly above the Tropic of Cancer, and does not rise south of the Antarctic Circle.
From the surface of the Earth, it appears that the Sun rises and sets. Everyday the Sun rises in the East and sets in the West; however, during certain times of the year, the Sun may follow a slightly different pattern. In the Northern Hemisphere when it is Winter, the Sun rises in the Southeast and sets in the Southwest. In the Spring and Fall the Sun rises in the direct East and sets in the direct West. In the Summer, the Sun rises in the Northeast and sets in the Northwest.
What is most interesting about this topic is that the students associate schooling and activities around the seasons. For example, they know that school begins in the Fall and ends in the Summer, with the Summer being a vacation time. They also know that we have a Winter break and Spring break during the school year. I believe that the students use these terms frequently because it is what is comfortable for them. However, it is unclear whether they grasp the understanding of why and how the seasons occur.
Comments: