Find objects around your home to make a scale model of our solar system! Mr. Downey is a Muscogee County School District Educator working at the Coca-Cola Space Science Center.

**Lesson: ** The Solar System is very large! Think about this: we sent a probe to Pluto back in 2006 which took 9 and a half years to reach Pluto at an average speed of 36,400 miles per hour! Compare that with commercial planes on Earth which travel close to 500 miles per hour. It’s sometimes easier to shrink the Solar System down to a smaller size so we have an easier time understanding it. In order to do this, we must shrink all planets at the same rate using ratios and proportions. We will take the Earth and shrink it down to the size of a Tennis ball, and all the other planets will scale down the same amount as the Earth does. Now it’s your job to find other objects around the house that you think have the same diameter as the other planets in the solar system. (Diameter means the distance across a circle in a straight line that passes through the center of the circle.)

Earth is the largest of the terrestrial, or rocky, planets, which means all objects found for Mercury, Mars, and Venus must have a smaller diameter than a tennis ball. Jupiter, Saturn, Uranus, and Neptune are the gas giants and must be larger than the diameter of a tennis ball. How large or small will be up to you to decide! The answers are given at the end of the video for you to find out how close you were to the correct answers.

**What did you learn? Try answering these questions: **I mention in the video that doing the distances of the planets would be quite hard to do without a large area to work with. But in the video, we failed to mention the Sun. **Using our same scale, how large do you think the Sun would be?** Do the math yourself to find out how large it would be in inches. (Yes, you can use a calculator for this.) Multiply 865,000 (miles) by 3 (inches/tennis ball) then take that answer and divide it by Earth’s diameter in miles, 7,918 miles. Another extra you could do is our Moon! Use the same formula above but substitute the diameter of the Moon in miles for the 865,000 value. Think about the different models of the Solar System you can buy in stores. **Now that you’ve done this activity, are the planets in these models the right scale size? Why or why not? **

Did you enjoy this activity? Please let us know and send an e-mail to us at **info@ccssc.org**