A Scale Model of the Solar System

Table of Contents

Objective
Introduction
Materials
Procedure
Questions
Glossary
Home

Objective:

Construct a scale model of the solar system to familiarize the student with the relative sizes and positions of the planets in the solar system and the vast distances between them and between the Sun and other stars. A convenient scale has 1 foot representing 1 million miles. This same scale has 1000 miles representing 1 light-year.

Introduction

From 1959 to the present, the National Aeronautics and Space Administration (NASA) has sent a number of spacecraft to explore our solar system. Many different types of spacecraft are used and many different kinds of scientific instruments gather data about the objects in our solar system. Spacecraft have flown by all the planets except Pluto and have encountered comets, asteroids, and all of the larger moons except Pluto's moon, Charon. Satellites have been placed in orbit around Venus, Earth, Mars, and Jupiter. Landers have explored the surfaces of Mars, Venus, and the Moon. Men have landed on the Moon and brought back new information about our solar system. Close-up photographs of distant planets and moons will be taken on future missions, and detailed radar maps of the cloud-hidden surface of Venus are still being analyzed.

Materials:

**Relative Sizes for Representing Objects**
Object & Scale Size	Representative Object	Distance from the Sun Model
Sun=10 1/2 inches	basketball	center
Mercury=1/28 inch	pinhead	36 feet (12 yards)
Venus=1/11 inch	map-pin	67 feet (22 yards)
Earth=1/10 inch	map-pin	3 inches from Earth
Mars=1/20 inch	pinhead	142 feet (47 yards)
Asteroids	dust	258 feet (86 yards)
Jupiter= 1 1/15 inches	1 1/4 inch ball	486 feet (162 yards)
Saturn=9/10 inch	7/8 inch ball	891 feet (297 yards)
Rings	2 inch diameter disk
Uranus=4/10 inch	1/2 inch ball	1794 feet (0.3 miles)
Neptune=4/10 inch	1/2 inch ball	2810 feet (0.5 miles)
Pluto=1/58 inch	pinhead	3695 feet (0.7 miles)
Nearest Star	basketball	4300 miles

Saturn's rings can be constructed by photocopying the ring diagram onto transparency material, cutting around the outside and cutting out the inside to fit over the 7/8 inch ball that represents Saturn (See bottom of page) . For additional realism, paint the planets and Saturn's rings with appropriate colors and details (see images below). (Mercury: gray; Venus: white; Earth: blue, white, brown, and green; Mars: red; Jupiter: off-white with reddish-brown bands and a red spot; Saturn: yellowish-white with white rings; Uranus: light, blue-green; Neptune: deep blue; Pluto: gray.)

Procedure:

Place the basketball representing the Sun at the "center" of your solar system. The pinhead representing Mercury is placed about 12 yards (12 adult paces or about the width of a typical classroom) from the Sun. The map-pin representing Venus is placed about 22 yards from the Sun and the map-pin representing Earth is placed 31 yards from the Sun. One can usually get the inner solar system, out to perhaps Mars, to fit within a long hallway or inside a gymnasium. If at all possible, it is quite informative to go outdoors and include at least Jupiter. For the rest of the outer planets, it is best simply to know where they would be. For example, use a car to measure 0.7 miles from the "Sun" and find a suitable landmark for the orbit of Pluto. Finally, note that the nearest stars, the Alpha Centauri system, are represented by a basketball and two other somewhat smaller balls placed some 4300 miles away. A world map or globe and a little imagination will be enough to envision how far away the real stars are.

Questions:

If you place yourself at the position of the model Earth, how large does the model Sun appear to be? (Hold up you thumb at arms length for comparison.)
How does this compare with the apparent size of the real Sun as seen from Earth? (Don't look directly at the real Sun. If the Moon is visible, you can use it for comparison since both the Sun and the Moon appear to be the same size.)
How large do the other model planets appear to be as seen from the position of the model Earth? Do you think you could see the pinhead sized model of Pluto placed 0.7 miles away?
With modern spacecraft, it takes about 10 years to travel from Earth to just beyond Pluto (about 1 mile in our scale model). How long would it take one of these spacecraft to travel to the nearest stars (4300 miles away in our scale model)?
All these planets travel in nearly circular orbits with the Sun at the center. When the Earth passes between Mars and the Sun, Mars is only 16 yards away (47-31 yards). When the Earth and Mars are on opposite sides of the Sun, Mars is 78 yards away (47+31 yards), about five times farther. How much larger will Mars appear at its closest compared to its appearance at its farthest?
Because of its greater distance from the Sun, Jupiter travels around the Sun in its orbit at about half the speed that the Earth travels. If it takes the Earth a year to travel around the Sun, how long does it take Jupiter to travel around the Sun?

To view true-color images of the planets and the Sun, click on each of the thumbnail images below.

Authors:

Developed by Dr. David H. Hathaway, NASA/MSFC
Converted to HTML by Clifford Schlecht, a SHARP student from Hazel Green High School

June 1998