Your Weight on Other Worlds

Ron Hipschman, San Francisco Exploratorium
Type Category
Instructional Materials
Numerical/Computer Model , Article
This resource, vetted by NSTA curators, is provided to teachers along with suggested modifications to make it more in line with the vision of the NGSS. While not considered to be "fully aligned," the resources and expert recommendations provide teachers with concrete examples and expert guidance using the EQuIP rubric to adapted existing resources. Read more here.



Students enter a weight on Earth, and view the equivalent weight on other planets, Pluto, Earth’s moon, some of Jupiter’s moons, and a few types of stars. The calculator/model is followed by a reading about the difference between mass and weight, and the relationship between gravity, mass, and distance.

Intended Audience

Educational Level
  • Middle School
Access Restrictions

Free access - The right to view and/or download material without financial, registration, or excessive advertising barriers.

Performance Expectations

MS-PS2-4 Construct and present arguments using evidence to support the claim that gravitational interactions are attractive and depend on the masses of interacting objects.

Clarification Statement: Examples of evidence for arguments could include data generated from simulations or digital tools; and charts displaying mass, strength of interaction, distance from the Sun, and orbital periods of objects within the solar system.

Assessment Boundary: Assessment does not include Newton’s Law of Gravitation or Kepler’s Laws.

This resource is explicitly designed to build towards this performance expectation.

Comments about Including the Performance Expectation
The purpose of the weight calculator and the reading are to show and explain the relationship between gravity, mass and distance. The data generated by the weight calculator can be used as evidence to support the claim. Information from the reading may be used as “evidence from the text” that supports the claim.

Science and Engineering Practices

This resource was not designed to build towards this science and engineering practice, but can be used to build towards it using the suggestions provided below.

Comments about Including the Science and Engineering Practice
Nowhere does the website overtly say “Hey, you can use this information as evidence to support a claim!” That part will be up to the class. This could be a good opportunity to discuss different types of evidence that can support a claim, as the website offers both evidence from a mathematical model and evidence from a text written by a reputable source. This offers an opportunity to connect with the Common Core standards for reading and writing in science. Students could also “dig into” the model to see what happens when they enter different weights. They could, perhaps, gather enough evidence to graph the relationship between weight entered and weight of the world (weight of the world is given when you click on the picture of that world). This could even be followed up by giving the students some fictional planets' radii and masses, and having the students calculate their weights on the fictional planets.

Disciplinary Core Ideas

This resource is explicitly designed to build towards this disciplinary core idea.

Comments about Including the Disciplinary Core Idea
The idea that there is gravity “on” large masses is the point of the mathematical model. The idea that ALL masses exert gravity on ALL other masses is explicit in the reading, but while it forms the basis for the calculations in the model, the idea is not made overt to users in the model section of the website.

Crosscutting Concepts

This resource is explicitly designed to build towards this crosscutting concept.

Comments about Including the Crosscutting Concept
The algebraic expression of the scientific relationship between mass, distance and gravity is shared in the reading portion of the website. This relationship is the "driver" of the mathematical model, though the algebraic expression is not specifically shown or stated in the model portion of the website. See the tips for Practice for some ideas about how to make the mathematics more overt if using only the model portion of the website.

This resource appears to be designed to build towards this crosscutting concept, though the resource developer has not explicitly stated so.

Comments about Including the Crosscutting Concept
It’s pretty clear that putting an input gives you an output, in the model portion of the website. It would be up to the class to overtly name the parts of the system, the inputs and the outputs. The website is not directly labeled as a model, and, to be specific, the students don't interact directly with the model (the mathematical equation that calculates their weights) so again it would be up to the class to make that connection. Energy and matter flows are not addressed.

Resource Quality

  • Alignment to the Dimensions of the NGSS: For the performance indicator: although the site itself does not direct students to use evidence to support a claim about the relationship between gravity, mass and weight, the site does offer two kinds of evidence that students can use to support the PI's claim. You may find a need for more sources and pieces of evidence to make a really strong support of the claim given in the standard. For the DCI: this website gives information about that exact topic of gravitational interactions. For the cross-cutting concept, the class could use the website to address it, but the website itself is not specifically meant for that purpose. For the practice: this website is a natural fit for gathering and using evidence.

  • Instructional Supports: My students find the model engaging. It shows them real stuff about real planets, moons, etc. The reading has a formula and also a poem, appealing to different modalities. The reading only comes in one reading level. The information is scientifically accurate, and the reading level is appropriate for middle school, with an average reading level (based on 5 reading-level-calculators) of grade 6.7.

  • Monitoring Student Progress: - none -

  • Quality of Technological Interactivity: The website includes an interactive model directly related to learning. The model is not individualized; it’s the same model for everyone. Students can, however, enter weights of their own choosing and get their "own" results. The model is well-designed, easy to use, and appealing. The model has never crashed or misbehaved in hundreds of uses with my students.