Sidewalk Solar System

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How far away is “next door” in space? The distances we experience here on Earth are far smaller than those out in space. Even in our planetary neighborhood, the solar system, the other planets are so far away the distances are hard to comprehend. In this activity, you will make your own scale model to visualize the distance between the planets in our solar system.

Age: 7+
Time: 20 minutes
Topics: solar system, scale distance, planets, models

What you need:

• Open space or sidewalk, 42 ft. – 84 ft. long
• 1 roll of toilet paper (for method 1)
• Markers (for method 1)
• Tape measure or yardstick (for method 2)
• Sidewalk chalk or 10 objects to mark planet locations (for methods 2 & 3)

What to do:

1. Decide which of the measuring methods below you will use: toilet paper squares, inches, or sidewalk squares. Make some predictions about how far apart the planets will be in your model. How far do you think your solar system will stretch across your yard or down your street? If Mercury is one toilet paper square away from the sun, how far away will Pluto be?

2. Gather your materials, find an open space, and use the charts below to measure the relative distances between planets. Note: Depending on the space you have available, you should choose either the "short" (42 ft.) or "long" (84 ft.) column of the chart.

Method 1 – Toilet Paper

• Lay the end of the toilet paper on the ground. (If you are outdoors, you may want to weigh the end down so it doesn’t blow away.) Draw or write something on the edge of the toilet paper to represent the Sun.
• Use the Toilet Paper Squares chart below to count the number of toilet paper squares to get to Mercury. Unroll the toilet paper to that point and use a marker to draw or write Mercury on that spot on the toilet paper. Continue unrolling and counting toilet paper squares until you get to the next planet and mark that spot. Remember that each distance is measured from the Sun, not from the previous planet. Keep going until you get to Pluto.

Method 2 – Inches

• Pick a spot on the ground and that will represent the Sun. Place your first object down there or mark that spot with sidewalk chalk.
• Follow the Inches chart and use your tape measure or yardstick to measure the distance to Mercury. Mark that spot with another object or use sidewalk chalk to write it on the ground.
• Continue measuring until you get to the next planet and mark that spot. Remember that each distance is measured from the Sun, not from the previous planet. Keep going until you get to Pluto.

Method 3 – Sidewalk Squares

• This method is most accurate if all the sidewalk squares you count are the same size. Check the area of sidewalk you plan to use to make sure you have 24 sidewalk squares that are all the same width. Otherwise, choose one of the other methods instead.
• Mark the location of the Sun at one end of your sidewalk with an object or draw it with chalk. Count 24 sidewalk squares from the Sun, and mark or draw the location of Pluto at that point.
• Use the Sidewalk Squares chart below to measure and mark the planets in between. (Note: This chart lists the planets in the order that is easiest for measuring, so it might look “out of order,” but the planets will all end up in the right places!)

3. When you are finished measuring, look along the distance to see how far away the outer planets (Jupiter-Pluto) are from each other and from the inner planets (Mercury-Mars). Is there anything you see that is surprising to you?

• How is this model like the actual solar system?
• What aspects of the solar system does it illustrate or help us understand?
• How is this model not like the solar system? What parts might be inaccurate or left out?

5.  Other ideas to try:

• Try using two of these methods (or even all three) and comparing them. How are they similar or different?
• Could you change the Sidewalk Squares chart to use it for a different length of sidewalk, like 20 squares or 32 squares? How would you do it?
• These methods used some unusual units of measurement: toilet paper squares and sidewalk squares. What other objects could you as units of measurement?  Create a scale model of the solar system measured in your own unit of measurement, like pencils, hand-widths, or your favorite toy!

Toilet Paper Squares:

 Planet Distance from Sun [mi] Distance in squares of toilet paper  [short version] Distance in squares of toilet paper  [long version] Mercury 35,983,600 1.0 2.0 Venus 67,232,000 1.8 3.7 Earth 93,000,000 2.5 5.1 Mars 141,635,000 3.8 7.7 Jupiter 483,632,000 13.2 26.4 Saturn 888,188,000 24.2 48.4 Uranus 1,784,000,000 48.6 97.3 Neptune 2,800,000,000 76.3 152.5 Pluto 3,675,000,000 100.0 200.0

Inches

 Planet Distance from Sun [mi] Distance in inches  [short version] Distance in inches  [long version] Mercury 35,983,600 4 8 Venus 67,232,000 7.2 14.8 Earth 93,000,000 10 20.4 Mars 141,635,000 15.2 30.8 Jupiter 483,632,000 52.8 105.6 Saturn 888,188,000 96.8 193.6 Uranus 1,784,000,000 194.4 389.2 Neptune 2,800,000,000 305.2 610 Pluto 3,675,000,000 400 800

Sidewalk Squares

 Planet Distance from Sun [mi] Distance in sidewalk squares Pluto 3,675,000,000 24 Uranus 1,784,000,000 12 Halfway between the Sun and Pluto Neptune 2,800,000,000 18 Halfway between Uranus and Pluto Saturn 888,188,000 6 Halfway between the Sun and Uranus Jupiter 483,632,000 3 Halfway between the Sun and Saturn Asteroid Belt 257,000,000 1.5 Halfway between the Sun and Jupiter Mars 141,635,000 0.75 (3/4) Halfway between the Sun and Asteroid Belt Venus 67,232,000 0.375 (3/8) Halfway between the Sun and Mars Earth 93,000,000 Halfway between Venus and Mars Mercury 35,983,600 Halfway between the Sun and Venus

What’s happening?

This activity is a model of the distances of the planets in our solar system. Models are important tools for scientists to explain ideas, objects, or processes that they can’t observe directly. Models often begin as simplified versions and are not usually completely accurate. As scientists gather more and more data they use it to improve their models and make them more and more accurate.

This model effectively illustrates the relative distances between objects in the solar system. However, it shows planets making a straight line going out from the Sun, which isn’t the case, since they are always in different places in their orbits around the Sun. Also, their orbits are ellipses (ovals) rather than perfect circles, so these distances are just average distances from the Sun.

Note: Pluto is classified as a dwarf planet rather than a planet. It is located at the beginning of the Kuiper Belt, an area beyond Neptune containing large numbers of cosmic objects, including comets, asteroids, and other dwarf planets such as Eris, Makemake, and Haumea.