Grade levels: 8–12 Time: 45 minutes Key concepts: modeling astronomical systems, motion and forces, the solar system Teaching Tips and National Science Education Standards See this page as a Word document | PDF (download Acrobat reader).

Activity

How much of the Sun will be covered as Venus passes between the Sun and Earth? To find out, we can build a scale model of the Sun, Venus, and Earth.

This illustration shows the path that Venus will take as it transits the Sun in 2004 and again in 2012. In 1996 Venus passed near the Sun and in 2020 Venus will pass nearby once again.

Materials (one set for every three students):
• a white paper plate, about 9 inches (23 cm) in diameter
• a transparency
• a manila folder
• a pair of scissors
• adhesive tape
• a fine-point permanent black marker
• meter sticks and/or tape measures, one for each group
• a location that is at least 100 feet (30.5 meters) wide
• binoculars (optional)

To Do and Notice
Facts we need to construct our scale model:

• The size of the real Sun is 864,938 miles (1,391,980 km) in diameter.

• The average distance between Earth and the Sun is about 92,976,000 miles (149,630,368 km) – or about 107 “Suns” laid end to end.

• The average distance between Venus and the Sun is about 67,221,648 miles (108,182,755 km) —or about 77 "Suns” laid end-to-end.

• Earth is 7,926 miles (12,756 km) in diameter. That means that 109 Earth’s laid end-to-end would equal the diameter of the Sun.

• Venus is 7,520 miles (12,102 km) in diameter. That means 115 Venuses laid end-to-end would equal the diameter of the Sun.

Let’s use the paper plate to represent the Sun. We need to figure out how big Earth and Venus would be using this scale. If 115 Venus’s fit across the Sun’s diameter, then at this scale, Venus’s diameter will be:

Venus model = 9 inches/115 = 0.078 inches (0.2 cm)

If 109 Earths fit across the Sun’s diameter, then at this scale, Earth’s diameter will be:

Earth model = 9 inches/109 = 0.082 inches (0.21 cm)

The man in the distance is holding the paper plate representing the Sun. The woman is holding the transparency with the mark that represents Venus. (Click to download larger image.)

• Cut the manila folder down the crease so that you have two pieces of cardboard that are 8.5 x 11 inches. Cut a large rectangular window out of the center of one of the pieces of cardboard and tape the transparency to one side. You now have made a cardboard frame that will hold the transparency rigid.

• In the center of the transparency, use the permanent marker to make a mark that is 0.1 inches (0.20 cm) in diameter. This will represent the Venus in our scale model.

• To create a scale model of the transit of Venus, we will need to place the Sun, Venus, and Earth in their proper positions. Have one student hold the paper plate representing the Sun just under his/her chin. To place Venus, have another student hold the transparency with the black mark a distance equal to 77 paper plates laid end to end, or …

Distance between Sun and Venus models = 77 x 9 in = 693 in ~ 58 ft (17.7 meters)

• To place Earth in its proper position, have another student stand a distance equal to 107 paper plates laid end to end, or …

Distance between Sun and Earth models = 107 x 9 in = 963 in ~ 80 ft (24.4 meters)

• To model the transit that will be visible on June 8, 2004, have the student representing Earth close one eye and position the other two students so that the mark on the transparency representing Venus crosses in front (or “transits”) the paper plate.

Other Things to Do and Notice/Resource Links to Go Further>>

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