Now impress the students further by shrinking the Sun's scaled size down to 3 inches, or about the size of an orange. Depending on the amount of time you want to spend on this activity, you may either present the students with the 3 inch model of the Sun and ask them to guess the size of each of the planets, or present objects that are the scaled sizes of Jupiter and Saturn and ask the students which planets they think these might represent. Objects that are good sizes for Jupiter and Saturn are popcorn kernels. (Saturn is about as big as Jupiter with its rings.) Other helpful sizes: .01 inches is about the size of a grain of sand; .1 inches is the thickness of a pencil point. Have the students calculate the scaled sizes of and distances to each of the planets. This can be done in small groups, with each group concentrating on one planet. Then have the students pace out the distance between the planets. (A football field is the best place to go.) Have the students spot inconsistencies in their calculations if mistakes are made. For example, demonstrate the problems that arise if they calculate Jupiter's orbit inside the Earth's. It is important to explain, however, that the planets do not always line up in a straight line, but orbit around the Sun. Use the Orbital and Rotation period data from Table III to explain the positions of the planets at any one time. Another remarkable concept to point out is that we can see the planets from Earth despite these distances. Once the distance to Pluto is discussed, mention (or have the students calculate) the distance to the nearest star. The distance in this scale to Proxima Centauri, the nearest star, is 1400 miles: about the distance from Trenton to Oklahoma City. Proxima Centauri is about one-tenth the size of the Sun, in this scale about .3 inches. Ask the students to imagine holding out a raisin to a friend in Oklahoma City and having them be able to see it. Explain that this extraordinary visibility is possible because stars are so incredibly bright.
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