Astronomy is one of the oldest sciences. All one needs to do is look up on a clear night and absorb the beauty of the star filled sky, or observe the magnificence of a solar or lunar eclipse. However, there are also more practical reasons for having an interest in astronomy. For example, the

Ancient Greeks knew about the connection between the seasons and the relative orientations of the Sun and Earth. Furthermore, seafaring cultures were aware that the tides are influenced by the position of the Moon.

Several ancient civilizations placed great importance on astronomical observations. Hundreds of impressive monuments, such as stonehenge, that dot the British Isles provide evidence of this emphasis on astronomical observation. For example, at stonehenge various stones point to the locations where the Sun and the Moon rise and set at key times during the year, such as the solstices and equinoxes. Another example is the great medicine wheel in Wyoming. The medicine wheel, constructed atop a windswept plateau by Native Americans. The wheel is a circular ring of stones where certain stones mark important astronomical events, such as the rising of bright stars and the Sun at the summer solstice.

The Aztec, Mayan, and Incan architects in Central and South America designed buildings to be astronomically oriented. For example, the city of Tiahuanaco, in Bolivia, the Temple of the Sun was built with its walls aligned north-south-east and west with an accuracy of better than 1 degree. The Egyptian pyramids also have their sides oriented north-south-east and west.

Eratosthenes was only one of several brilliant astronomers to emerge from the Alexandrine school, which by his time had a distinguished tradition. For example, one of the first Alexandrian astronomers, Aristarchus of Samos, had devised a method of determining the relative distances to the Sun and Moon, perhaps as long ago as 280 BC. He concluded that the sun is only 20 times farther from us than the Moon. We now know that the average distance to the Sun is about 390 times larger than the average distance to the Moon.

However, Aristarchus also made an attempt to determine the relative sizes of the Earth, Moon and Sun. By observing how long it takes for the Moon to move through the Earth's shadow, Aristarchus estimated the diameter of the Earth. He also realized that the Sun and Moon have the same angular size in the sky, thus based on this observation he was able to determine the size of the Sun.

Ancient astronomers, particularly those of Greece, gave us a new and powerful way of thinking about the world. They gave the first clear demonstration that the tools of logic, reason, and mathematics can be used to discover and understand the workings of the universe. At the present time we have tools that we can use to model the universe and ask very profound questions regarding our model of the solar system to gain an understanding of our wondrous solar system. This questioning is what we will do for our 2^nd project.

This project requires quite a bit of planning before hand. You should create a plan with your teammates on what needs to be done who needs to do it and how it needs to be done. This includes gathering information concerning the Earth-Moon-Sun system, determining viewpoints.

It is also useful to keep a log notebook that contains data concerning what you have done and how your team decided to demonstrate astronomical concepts. This is useful for two reasons: 1. Allow you and your team to discuss what needs to be included in your compare/contrast papers. 2. Provide a coherent and concise presentation concerning your project.

Remember that you will have visitors to your web site and they will want to learn about astronomy as well. Thus, your model will have to be able to answer questions that users will ask. Some questions are:

• What are the differences between a full Moon and Lunar Eclipse?
• Does the Sun ever rise on the Moon?
• What, if any, do the phases of the Earth look like from the Moon?
• What are differences between sidereal and synodic periods for the Earth and Moon?
• What conditions are required for a solar eclipse?
• Where are the Van-Allen radiation belts on the Earth and the Moon?
• What are the differences and similarites between the Earth, Sun and Moon interiors and atmospheres?

Remember: Be on the lookout for astronomical phenomena that may be difficult to measure and stay aware of how that affects your model as compared to the real solar system. Also, in order to demonstrate a phenomenon your team must locate the necessary information. Your text book is a wonderful resource for the Earth-Moon-Sun system.

Also the following links have good information concerning the Earth, Moon and Sun.

• University of Tennessee: Introductory Astronomy
• Foundations of Astronomy
• The Nine Planets (very complete and easy to use site)