Science and Myth
Throughout the ages different cultures have speculated on why the seasons happen as they do. The ancient Greeks thought that the seasons were the result of the unfortunate marriage between Persephone, the daughter of the goddess of the harvest, and Hades, the god of the underworld. Ancient Navajo Indians believed the seasons were caused by the aging of Estsanatlehi as the seasons passed from spring to winter until she was reborn with the next spring.
Over the ages, cultures have come up with wonderful stories to explain the phenomenon of seasons. At the same time ancient astronomers were remarkably accurate in their calculations and predictions of patterns in the cosmos. Only in the past few centuries have scientists formulated a model that can account for such diverse patterns as moon phases, the frequency and duration of lunar and solar eclipses, and seasonal fluctuations in day length or the sun's apparent path in the sky.
The following sites tell us more about the myths and the science of seasonal change.
Why is your shadow longer in winter than in summer? It's easy to see the answer if you have a "sun" and an orbiting "earth" to demonstrate. Like many other ancient people, the ancient Chacoans used the annual changes in shadows to measure the passage of time and the change of seasons. In this activity, you'll see how the sun's tilt on its axis changes the length of shadows.
About 2,000 years ago the Greek astronomer Hipparchus discovered that the position of the Sun at any season, measured against the background stars, migrates in a slow cycle of about 26,000 years. This "precession of the equinoxes" also shifts the position of the celestial pole (so that our pole star would not have been a good guide for the ancient Greeks) and is caused by the rotation axis of the Earth slowly moving around a cone. MSP full record
This section of the Windows to the Universe web site provides detailed information about the motion of planets and the seasons. The web site spans the Earth and space sciences and includes documents, images, movies, animations, and data sets. Links at the top of each page allow users to navigate between beginner, intermediate and advanced levels. MSP full record
In this lesson plan, students pretend to be historians and use web sites to find information about how ancient cultures kept track of and celebrated the seasons. The students compile their findings into posters or illustrated reports. MSP full record
This educational program from NASA provides background information and class activities related to ancient cultures' use of the sun and other objects in the sky to mark the passage of time and to predict seasons and special events. In an activity, students make sun shadow plots by marking ends of shadows made by the sun and a gnomon (a stick used to cast shadows) to determine the direction of true north. As they perform this activity, students will gain experience in measuring angles; collect and analyze data in order to make predictions; use the angle bisector method to find true north; and use ratios to predict the length of shadows cast by the different lengths of the gnomon. MSP full record
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Copyright
June 2007 — The Ohio State University. This material is based upon work
supported by the National Science Foundation under Grant No. 0424671. Any
opinions, findings, and conclusions or recommendations expressed in this
material are those of the author(s) and do not necessarily reflect the views of
the National Science Foundation.
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