The Reason for the Seasons
Unless you live near the equator you will likely have noticed that the seasons change throughout the year. On our planet Earth the year can be separated into four distinct seasons: summer, autumn, winter, and spring. Each season brings with it physical changes in weather, temperature, and the length of daylight. We also mark the change of seasons with special events and activities, with changes in fashion and food -- even our attitudes may change.
Throughout history many different cultures have created stories and reasons to explain the seasons:
- In ancient Greek mythology the story of Persephone is used to explain the seasons. Persephone is the daughter of Demeter, Goddess of the Cornfield. One day while Persephone is out picking flowers the ground beneath her feet opens up and out comes Hades, God of the Underworld. Hades is in love with Persephone and he scoops her up and takes her back to the underworld with him. Persephone's mother, Demeter, is heartbroken and because of her sadness she decides not to let anything grow on earth - no flowers, no trees, and no food crops. The earth becomes a wasteland. The other Gods and Goddesses beg Demeter to let the plants grow but she refuses. Zeus, the head God, demands that Hades return Persephone to her mother but this can only happen if Persephone has not eaten any food from the underworld. It turns out that Persephone has eaten six pomegranate seeds. So, it is decided that for six months Persephone will be allowed to live with her mother on earth but for the other six months of the year, one month for every seed she ate, she will be forced to live in the underworld with Hades. The six months that Persephone is on earth are Spring and Summer and her mother lets all of the flowers and plants bloom because she is happy to be with her daughter again. During the Fall and Winter, when Persephone is in the underworld, the plants stop growing because Demeter is sad and misses her daughter.
- In Native American mythology one story tells about how the seasons were created. Originally the earth had only known summer but the living things on the planet were always complaining about one thing or another and Tobats, an elder god, decided he would give them something worth complaining about. He poured snow all over them and this is how winter began. The planet now had two seasons, the summer and the winter. The living things on earth came together for a meeting to discuss the seasons. The owl told about what he saw: the Weather Man makes the weather go back and forth on a long, straight trail with his home right in the middle. When the Weather Man goes north, Tom, the winter, follows him and it becomes cold on earth. When the Weather Man travels to the south, Tats, the summer, follows him and the planet experiences summer. The living things, however, thought each season was too long and they asked the younger god, Shinob to make the seasons shorter in length by cutting the Weather Man's trail. He said he could not do this because the length was permanent but if they came up with a better plan and they all agreed, he would make the changes. The night bird suggested that there be four seasons instead of two and that the trail be made into a circle rather than a straight line. The weather trail would go around each corner of the earth, the four seasons would be taman (spring), tats (summer), u-wan (fall) and tom (winter). Weather Man would go around the circle in the same direction and the seasons would be the same length, following each other in the same order year after year. Everyone agreed and the plan was set into motion.
The annual seasons happen because of two reasons:
- There is a 23.5° tilt in the earth's axis and this makes our planet rotate like a gyroscope.
Our planet never stands upright — it is always leaning to the side.
The direction of this lean never changes.
- The earth revolves around the sun in an elliptical orbit.
As the Earth travels along its orbit, it sometimes leans toward the sun and sometimes away from the sun.
It takes our planet 365.25 days to make one trip around the sun.
Other Activities & Web Sites to Help Explain the Seasons:
Because the direction of the Earth's tilt changes in relation to the sun, the northern and southern halves (hemispheres) of our planet get different amounts of sunlight throughout the year. When the Northern Hemisphere of the Earth is leaning toward the sun, it receives direct rays of sunlight and is warmer, while the Southern Hemisphere receives more indirect rays. When the northern part of the Earth is leaning away from the sun, the situation is reversed—the Northern Hemisphere gets cooler, more indirect sunlight while the southern half receives direct rays and experiences warmer temperatures. Because of this, the seasons in the Northern and Southern Hemispheres are reversed.
|The summer solstice is the first day of summer and the longest day of the year. In the Northern Hemisphere the summer begins on or near June 21st, when the North Pole is leaning more directly toward the sun than it does on any other day. In the Southern Hemisphere summer begins on or near December 21st.|
|The winter solstice is the first day of winter and the shortest day of the year. In the Northern Hemisphere the winter begins on or near December 21st, when the North Pole is leaning away from the sun. In the Southern Hemisphere winter beings on or near June 21st.|
|The autumn equinox marks the beginning of fall and is a transitional period between the summer and winter seasons. In the Northern Hemisphere autumn begins on or near September 22nd, when the North Pole begins to lean away from the sun. In the Southern Hemisphere autumn beings on or near March 20th.|
The vernal equinox marks the beginning of spring and is a transitional period between the winter and summer seasons. In the Northern Hemisphere autumn begins on or near March 20th, when the North Pole begins to lean toward the sun. In the Southern Hemisphere autumn beings on or near September 22nd.