Supermarket Space Science – Scale of the Solar System

Guidelines for Teachers and Outreach Programs

This sheet contains materials lists and guidelines for running the BSU Observatory Scale of the Solar System activity. Included are suggestions for substitutions, expansions, and adaptations for various audiences. This sheet is not intended for distribution to students as part of an activity.

Description:

This activity puts the sizes of the Sun and planets in perspective with the distances between them by constructing the smallest possible scale model of the solar system with visible planets. Once the Sun is placed, the students pace out the distances to each planet. It requires a long hallway or large open space, and even then all of the planets will likely not fit in the area. Any planets that do not fit in the space available are “imagined” placed at local landmarks, as are the furthest comets and the closest star to the Sun. This activity typically takes 30 – 45 minutes with K-12 students and is most appropriate as presented for K-5th graders, but can be adapted for any age (see adaptation/expansion section).

Goals:

  • To correct the common misconception that planets in the solar system are near each other.
  • To place planets’ sizes compared to the Sun’s in perspective.
  • To realize just how large the distances between objects in space are.

Materials:

Each student receives a set of “planets.” There is one Sun for the whole class. Items listed below are those used by the BSU Observatory, but other objects of similar size could be substituted. The objects in parentheses are optional. Note: Be aware that the items below are food items. Always ask before running the activity whether anyone has a food allergy.

Sun – a whole grapefruit

Mercury – a grain of sugar

Venus – a poppyseed

Earth – a round sprinkle

Moon – a very small grain of sugar

Mars – a grain of corn meal

(Asteroids – an empty Tupperware, with the air inside representing microscopic asteroids. One for the whole class only).

Jupiter – a piece of Kix

Saturn – a dry, uncooked black bean [Note: this represents the size of the planet without the rings].

Uranus – a piece of couscous

Neptune – a whole peppercorn

Pluto – a grain of sugar

(Small zip-top bags to contain each person’s planets are also helpful).

Step-By-Step:

1. Hold up the “Sun” (grapefruit) and ask the students how big the Earth would be if the Sun were really the size of the grapefruit. Let them guess. Once someone gets very close or they run out of ideas, hold up an “Earth” (round sprinkle). You can tell them that over 100 Earths fit across the center of the Sun, and it would take 1 million Earths to fill up the Sun like gumballs in a gumball machine. An average sunspot is larger than the Earth.

2. Pass out a set of planets to each student. You can then ask them a series of questions about which items represent which planets. For example, the Kix is the largest item – ask which planet is the largest. Another interesting thing to note is that the bean representing Saturn is not round, but instead is much flatter on one side (and so is Saturn).

3. Ask them about asteroids. Do they know what an asteroid is (a small, irregularly-shaped rocky object orbiting the Sun)? Do they know where most of them are in the solar system (between Mars and Jupiter)? How big do they think an asteroid would be on our scale (microscopic, for most of them)? Microscopic air molecules represent the asteroids in our scale (if using it, you can hold up the empty tupperware full of air). (Also optionally, mention the largest asteroid, Ceres, as a single grain of flour).

4. It is time to pace out the distances between the Sun and planets. Place the Sun in a visible location, preferably at one end of a long hallway or a large open space, such as a football field. Using small steps to represent about one foot each, walk away from the Sun and count the number of feet up to Mercury. Have the students count the steps with you. Stop when you reach Mercury’s location and turn back to look at the grapefruit. It should look larger to you now than the Sun does from the Earth. (Optional – leave a grain of sugar representing Mercury in the spot where you stop).

5. Repeat the above process for each planet and any optional objects you decided to include. When you reach Earth’s location, the grapefruit should look about the same size as the Sun does from the Earth – but you probably won’t be able to even see Mercury. As you get further from the grapefruit, it will get smaller and smaller, representing how the Sun looks smaller and dimmer from planets further away from it.

6. At some point, you will reach the edge of the space you are using. For any remaining planets, point out landmarks at which they would be. Also give the name of a town or city about 35 miles away as the location of the furthest comets that orbit the Sun, and the name of a State about 1800 miles away as the location of the nearest star system (Alpha Centauri).

7. Close by asking the students if they have any questions.

Tips From Experience:

  • The step-by-step is only a guideline – you do not have to follow it exactly.
  • The step-by-step is written from the perspective of an adult running an outreach session for a group of K-5 kids, but this activity translates directly into a classroom setting and can be adapted for various audiences. (See adaptation/expansion section below).
  • Kids often surprise us by asking unexpected questions. We find that following their lead into a topic to explore is engaging both for them and us.
  • Encourage them by asking them what they see at various steps during the activity (for example, when you reach Jupiter’s location, ask if they can see the Earth – does their answer make sense based on what they see in the sky at night?).
  • Kids usually get excited about pacing out the planets’ locations. Some will take huge steps or run ahead. Be a good example by keeping yourself to the small steps, and calling the runners back when you reach the right spot.
  • Choose a safe location to pace out the planets’ locations with students. Do not plan to cross any streets. If possible do this in a contained area, like a hallway or schoolyard.
  • Every once in a while, students decide to eat one or more of their planets (especially the peppercorn!). This emphasizes the need to ask about food allergies at the start. Also instruct the students not to eat their planets. If you need to substitute something for one of the planets, avoid using any product containing nuts as this is a severe allergen that is relatively common.
  • If you are worried about using food products for the above reason, there is the option of making small paper cutouts of approximately the right size. Colored construction paper can be used to make the cutouts more visible. For younger students, making the cutouts can be part of the activity.
  • We allow each student to keep their set of planets (which is another reason why we place them in zip-top bags). We feel that this minimizes germ-passing between groups of students, and that they enjoy having something to take home with them.
  • We pass out a small leaflet to each student to take home with them that includes a summary of the information in the activity and vocabulary words.
  • Be familiar with the information in the fact sheet. It will help you answer common questions and engage in conversations about the topic with students and/or their parents.

Adaptations and Expansions:

  • Dwarf Planet Expansion:
  • Additional Materials – extra sugar and flour
  • Extra time – 5 to 10 minutes
  • In 2006, Pluto was re-classified as a dwarf planet by the International Astronomical Union (IAU). They defined a planet as something that has enough gravity to pull itself into a round shape, orbits the Sun, and has cleared its orbit of debris. Pluto does not meet the third criterion, because it orbits within the Kuiper belt (which is loaded with comets). So, Pluto became known as a dwarf planet, and other objects similar to Pluto have, too.
  • Pluto and other large dwarf planets (Eris and Sedna) can be represented with small grains of sugar. Smaller ones (Ceres, Haumea and Make-make) can be represented with grains of flour. You do not have to mention every dwarf planet (the list keeps getting longer!).
  • Discuss the difference between a planet and dwarf planet, and name the existing dwarf planets.
  • Resources for learning more about dwarf planets:
  • The IAU’s page:
  • Mike Brown’s Dwarf Planet Page:
  • Google Maps Expansion:
  • Additional Materials – computers
  • Ask students to find the name of a town that is about the right distance away from your location to represent the following in your scale model of the solar system:
  • The location of dwarf planet Sedna (7 miles away).
  • The location of the edge of the solar system (34 miles away).
  • The location of the nearest star system, Alpha Centauri (1800 miles away).
  • Use the driving distance to represent the distance on the scale model – it doesn’t have to be exact.
  • Construction Paper Cutouts – Adaptation for Pre-K-2nd graders:
  • This version is not as accurate a representation as the version run by the BSU Observatory, however it still gets the same ideas across.
  • Optionally can be used to teach measuring with a ruler.
  • No food products needed.
  • Additional Materials:
  • Colored construction paper cut into small squares: gray (Mercury), white (Venus), dark blue (Earth), red (Mars), tan (Jupiter), yellow (Saturn), light blue (Uranus and Neptune), black (Pluto).
  • Safety scissors
  • Increase the size of the Sun in the scale to 6 inches – you can use a small paper plate.
  • Each student cuts out his/her own planets out of the colored squares. Mercury, Mars and Pluto – 1/16 inch. Venus and Earth – 1/8 inch. Jupiter –¾ inch. Saturn – 5/8 inch. Uranus and Neptune – ½ inch. You can do this by having the students measure, or already have circles drawn for them to cut out.
  • Multiply all the distances to pace by 1.33 (to still be relatively accurate – if you are concerned with the planets fitting in your space or you don’t want the students to have to walk too far, skip this).
  • The steps are the same otherwise.
  • Making a Scale Model - Adaptation for 6th – 12th graders:
  • Additional materials:
  • The calculation sheet provided separately
  • Pencil
  • Calculator
  • Extra objects to potentially represent planets (for example, salt, marbles, tennis balls, golf balls – various sizes).
  • Extra Time: 15 – 45 minutes
  • Provide the students with real sizes of the planets and real distances between them and ask them to calculate how big they should be if the Sun in your scale model is 4 inches wide.
  • The time this takes can be shortened greatly by having the students work in groups and having each group only do one or two planets.
  • Objects are chosen by the students from those provided to represent the sizes of their planets based on what they calculated. They should compare the objects they chose to see if their choices make sense.
  • The students provide the distance measurements in feet. The teacher/facilitator should write these numbers on the board so the whole class participates in deciding how far the distances should be.
  • When objects and distances are adequate, pace the distances out with the objects as a group.