Size-Distance Scale for the Sun, Earth, and Stars

The Space Science Institute offers fun kinesthetic Astronomy lesson plans targeted for 6th-8th graders.  The lessons are designed to support a constructivist, inquiry-based approach to teaching and learning that is aligned with standards for science education. 

I couldn't think of a better way to put the size-distance scale for the Sun, Earth, and Stars into prospective, than with this engaging activity!

The Proper Size-Distance Scale for the Sun, Earth, and Stars

1. Gather students outside, or a space at least 50 feet long.  Use an object the size of a large grapefruit to represent the size of the Sun.  Ask students to use their hands to predict how big Earth would be compared to the grapefruit on this 1:10 billion scale.

2.  When students have established their predictions, tell them on this scale Earth would only be as bis as the tip of a ballpoint pen (the Sun has a diameter 100 times that of Earth).  Next, ask students to  predict where Earth would be located in the model by walking away from the grapefruit sun to the location.

3.  When students have arrived at their predicted locations, pace out the 15 meters (50 ft.) to where Earth belongs.  Gather the class around you and explain that in the scale model, Earth would be 15 meters away (the actual distance is 150 million km).  Also, tell them Pluto (the retired planet) would be 0.5 mile away.

4.  Ask: What is the next closest star to our Sun?(Alpha Centauri)  
Explain: A light year is a unit of distance.  It is the distance light can travel in a year.  Light moves at a velocity of about 30,000 kilometers (km) each second.  In one year, light can travel 10 trillion km.
Ask: Approximately how far would you predict Alpha Centauri is from our Sun? (4.3 light-years)  

5. Tell students to assume that the grapefruit Sun is located in California.  
Ask:  In the scale model, where would the next grapefruit star be located? (4 MILLION meters or 2500 miles away) That is like having the grapefruit sun in California and the nearest grapefruit star in New York!!!

6.  Tell students that the Sun and Alpha Centauri are only two of 100 billion stars in our galaxy called the Milky Way, and furthermore; the Milky Way is one of 100 billion galaxies in our very large Universe.