Explore! Jupiter's Family Secrets

Heavyweight Champion: Jupiter


Heavyweight Champion: Jupiter! is a 30-minute activity in which children confront their perceptions of gravity in the solar system. The children weigh themselves on scales modified to represent their weights on other worlds to explore the concept of gravity and its relationship to weight. They consider how their weights would be the highest of all the planets while standing on Jupiter, but their mass remains the same no matter where in the solar system they are! They compare the features of different planets to determine which characteristics cause a planet to have more or less gravity.

This activity should be conducted before The Pull of the Planets in order for the children to better understand gravity before they model it. These concepts involve more advanced science than previous activities in Jupiter's Family Secrets, and they explore more deeply the science of the Juno mission and the rich information it will return to us. Facilitators who choose to undertake this activity should have a firm grasp of the scientific basis so that misconceptions are not introduced to the children.

This series is appropriate for children ages 10 to 13.

What's the Point?

  • Planets have measurable properties, such as size, mass, density, and composition. A planet's size and mass determines its gravitational pull.
  • Gravity alone holds us to Earth's surface.
  • A child's weight is determined by his or her mass and the gravitational pull of the planet.
  • Jupiter is not only the largest planet in our solar system, it is the most massive. A child standing on Jupiter would weigh more than on any other planet.


For each group of 10 to 20:

  • Computer and projector to show a brief movie of an astronaut walking on the Moon, such as Moon Walk
  • 3–9 "solar system scales," prepared as described under "Preparation" using:
  • 3–9 posters (one for each "solar system scale"), prepared as described under "Preparation" using:
  • Optional: 1 set of Our Solar System lithographs (NASA educational product number LS-2013-07-003-HQ), preferably double-sided and in color

For each child:

For the facilitator:


  • Review the complete background information and the Facilitator's Guide to Gravity.
  • Select the number of scales to offer and which planets you'd like to feature. It is not necessary to provide a scale for every planet, but we recommend offering at least three, including Earth and Jupiter.

Caution: Offer a Saturn scale ONLY to advanced audiences who are prepared to tackle the high–level concepts broached by this "trick" planet.

  • Prepare the scales: You will be altering each scale to represent the gravity of a different planet. First, remove the clear plastic covering to reach the dial with the numbers on it. Then cover each number with Wite-Out and replace it with the appropriate number for that planet using the Solar System Scales Guide. Leave one scale unaltered to provide the children's weight on Earth. Label each scale with the appropriate planet's name.
  • Prepare posters about each planet for which you have a scale. If desired, decorate them with the appropriate Our Solar System lithograph. Use Family Portrait...in Numbers to include all of the following details:
    • Type of atmosphere
    • Distance from the Sun
    • Planet mass
    • Planet diameter
    • Planet temperature
  • Post each planet's poster (perhaps in addition to the children's posters from Jump Start: Jupiter!) near the corresponding scale. If you are providing books about each planet, display them near the scale for the children to look through for more information.
  • Set up the computer and projector.


1. Ask the children to consider what it would be like to explore other worlds in our solar system.

  • Would they experience gravity on other planets and our Moon? How could we find out? Accept all answers.
  • Do we experience gravity on Earth? How?It holds us to Earth's surface.

Optional: Invite the children to jump and test this principle for themselves.

  • Astronauts have already visited the Moon; did they experience gravity there? Accept all answers.

2. Play one or more movies of an astronaut walking on the Moon and assess their opinions.

  • Now what do they think:  Does the Moon have gravity? Yes.
  • Does it have the same amount of gravity as Earth? Less.
  • Which planet characteristics cause a planet to have more or less gravity?  Consider the following variables: presence of an atmosphere, planet diameter, planet mass, planet temperature, and/or distance from the Sun. Which do they think is most important in determining a planet's gravitational strength? Accept all answers.

Invite the children to write their hypotheses in their journals.

Facilitator's Note: There are many different misconceptions about gravity; children may think that it is related to an object's motion, proximity to Earth or the Sun, temperature, magnetic field, atmosphere, or other unrelated concepts. Guide conversations cautiously and listen carefully to what the children say to avoid supporting their misconceptions.

3. Discuss the concepts of weight and gravity.

  • We can test for ourselves that gravity holds us to Earth's surface by jumping up and seeing that we came back to the ground. Would it be more or less difficult for say, a rhinoceros to jump as high as we did? Why? It would be harder because they weigh more.
  • Would the same rhinoceros be able to jump higher or lower on the Moon? Higher. There is less gravity on the Moon so the rhinoceros would weigh less.
  • How about on Jupiter? Accept all answers.

4. Invite the children to test how much they would weigh on other planets! Ask them to weigh themselves on the scales you modified to see what effect each planet's gravity would have on their weights. In their journals, invite them to record their measurements for each scale. In addition, ask them to note the characteristics for each of those planets.

  • On which planet did they weigh the most? Jupiter.
  • What do the children think it would feel like to weigh that much? Have they ever carried a 100–lb. backpack? What would it be like to feel that kind of weight not only on your back, but your hands, legs, feet, and head?
  • On which planet did they weigh the least?
  • How high do they think they could jump on that planet?
  • On which planet did the children have the most mass? The least? Trick question! Remind the children of their discussions during Dunking the Planets. While their weights varied, the children had the same mass on every planet.

Facilitator's Note: If you have a Saturn scale, they might notice that they weigh about the same on Saturn and Earth, because Saturn's gravitational pull is about the same as Earth's at its cloudtops (which are far above the planet's bulky — and gravitationally strong — center). Because the force of gravity depends on both mass and distance, planets that are less dense have less gravity at their cloud-tops or surfaces, which are far above the bulk of the mass in their interiors. This is why planets like Saturn appear to have less gravity than Neptune, despite Saturn's greater mass. You may need to remind the children of what they learned in Dunking the Planets in order for them to understand these difficult concepts.

You may also find that different sources report a range of weights/gravity for both Jupiter and Saturn. The point of this activity is simply to gather the sense that the children would weigh different amounts on the different planets, which can be seen regardless of which source is used to define the weight on the planets.


5. Invite the children to consider the planet properties they discovered in Jump Start: Jupiter and recorded in their journals. Alternatively, ask them to research planet properties in books or consider a copy of Family Portrait...in Numbers. Allow them time to consider the hypotheses presented in their journals and form their own conclusions.

  • Which properties cause a planet to have more or less gravity? Planets that are massive for their size have the most gravity.Which properties do not influence gravity? The presence of an atmosphere, temperature, and distance from the Sun do not affect a planet's gravity.


Invite the children to share their conclusions about the gravity in the solar system.

  • Everyone weighed the most on Jupiter; in other words, Jupiter had the strongest gravitational pull of all the planets. What properties make Jupiter the heavyweight champion? Jupiter has the greatest mass and size of all the planets.
  • What allowed Jupiter to beat out Saturn, a close contender in size? Jupiter is more dense than Saturn; it has more mass for its size.
  • What planets are not even contenders? Why? The inner planets are all much smaller and have much less mass than the giant planets.
  • Which planet would the children like to visit someday? Would they be able to jump higher or lower there?
  • Would they want to visit Jupiter? What kind of gravity will the Juno spacecraft experience as it approaches and orbits Jupiter? Juno will experience a strong gravitational pull.

If possible, build on the children's knowledge by offering them a future Jupiter's Family Secrets activity. Invite the children to return for the next activity, The Pull of the Planets, where they will discover how gravity governs the motions of the solar system!

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