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This simulation, recently rewritten to HTML5, provides an array of tools to help students visualize how gravity controls the motion of solar systems and how different variables affect the strength of gravity. Choose a system of star/planet, star/planet/moon, or planet/satellite, adjust the masses of star or planet, turn on velocity and gravity force vectors, and drag objects to relocate. What happens if gravity is turned off? What happens to the orbit if the star's mass is increased? The model can be adapted for use in Grades 7-12, as well as lower-level undergraduate courses.

This resource is part of the PhET project, a growing collection of simulations and teacher-created support materials for secondary teachers and learners.
Subjects Levels Resource Types
- Fundamentals
= Gravity
= Kepler's Laws
- Solar System
Classical Mechanics
- Gravity
= Orbits
= Universal Gravitation
- Motion in Two Dimensions
- Newton's Second Law
= Interacting Objects
- High School
- Middle School
- Lower Undergraduate
- Instructional Material
= Activity
= Interactive Simulation
Intended Users Formats Ratings
- Learners
- Educators
- text/html
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Access Rights:
Free access
© 2017 University of Colorado at Boulder
Additional information is available.
Earth/Sun/Moon system, Kepler's Laws, circular motion, gravitational attraction, gravity force, orbits, planetary orbits
Record Cloner:
Metadata instance created December 27, 2018 by Caroline Hall
Record Updated:
December 27, 2018 by Caroline Hall
Last Update
when Cataloged:
August 15, 2017
Other Collections:

Next Generation Science Standards

Motion and Stability: Forces and Interactions (MS-PS2)

Students who demonstrate understanding can: (6-8)
  • Construct and present arguments using evidence to support the claim that gravitational interactions are attractive and depend on the masses of interacting objects. (MS-PS2-4)

Earth's Place in the Universe (MS-ESS1)

Students who demonstrate understanding can: (6-8)
  • Develop and use a model to describe the role of gravity in the motions within galaxies and the solar system. (MS-ESS1-2)
  • Analyze and interpret data to determine scale properties of objects in the solar system. (MS-ESS1-3)

Motion and Stability: Forces and Interactions (HS-PS2)

Students who demonstrate understanding can: (9-12)
  • Analyze data to support the claim that Newton's second law of motion describes the mathematical relationship among the net force on a macroscopic object, its mass, and its acceleration. (HS-PS2-1)

Earth's Place in the Universe (HS-ESS1)

Students who demonstrate understanding can: (9-12)
  • Use mathematical or computational representations to predict the motion of orbiting objects in the solar system. (HS-ESS1-4)

Disciplinary Core Ideas (K-12)

Forces and Motion (PS2.A)
  • For any pair of interacting objects, the force exerted by the first object on the second object is equal in strength to the force that the second object exerts on the first, but in the opposite direction (Newton's third law). (6-8)
Types of Interactions (PS2.B)
  • Gravitational forces are always attractive. There is a gravitational force between any two masses, but it is very small except when one or both of the objects have large mass—e.g., Earth and the sun. (6-8)
  • Forces at a distance are explained by fields (gravitational, electric, and magnetic) permeating space that can transfer energy through space. Magnets or electric currents cause magnetic fields; electric charges or changing magnetic fields cause electric fields. (9-12)
The Universe and its Stars (ESS1.A)
  • Patterns of the apparent motion of the sun, the moon, and stars in the sky can be observed, described, predicted, and explained with models. (6-8)
Earth and the Solar System (ESS1.B)
  • The solar system consists of the sun and a collection of objects, including planets, their moons, and asteroids that are held in orbit around the sun by its gravitational pull on them. (6-8)
  • Kepler's laws describe common features of the motions of orbiting objects, including their elliptical paths around the sun. Orbits may change due to the gravitational effects from, or collisions with, other objects in the solar system. (9-12)

Crosscutting Concepts (K-12)

Patterns (K-12)
  • Patterns can be used to identify cause and effect relationships. (6-8)
  • Different patterns may be observed at each of the scales at which a system is studied and can provide evidence for causality in explanations of phenomena. (9-12)
Cause and Effect (K-12)
  • Cause and effect relationships may be used to predict phenomena in natural or designed systems. (6-8)
Scale, Proportion, and Quantity (3-12)
  • Time, space, and energy phenomena can be observed at various scales using models to study systems that are too large or too small. (6-8)
  • The significance of a phenomenon is dependent on the scale, proportion, and quantity at which it occurs. (9-12)
Systems and System Models (K-12)
  • Systems may interact with other systems; they may have sub-systems and be a part of larger complex systems. (6-8)
  • Models can be used to predict the behavior of a system, but these predictions have limited precision and reliability due to the assumptions and approximations inherent in models. (9-12)
Scientific Knowledge Assumes an Order and Consistency in Natural Systems (1-12)
  • Science assumes that objects and events in natural systems occur in consistent patterns that are understandable through measurement and observation. (6-8)
  • Science assumes the universe is a vast single system in which basic laws are consistent. (9-12)

NGSS Science and Engineering Practices (K-12)

Constructing Explanations and Designing Solutions (K-12)
  • Constructing explanations and designing solutions in 6–8 builds on K–5 experiences and progresses to include constructing explanations and designing solutions supported by multiple sources of evidence consistent with scientific ideas, principles, and theories. (6-8)
    • Apply scientific ideas to construct an explanation for real-world phenomena, examples, or events. (6-8)
Developing and Using Models (K-12)
  • Modeling in 6–8 builds on K–5 and progresses to developing, using and revising models to describe, test, and predict more abstract phenomena and design systems. (6-8)
    • Develop a model to predict and/or describe phenomena. (6-8)

AAAS Benchmark Alignments (2008 Version)

4. The Physical Setting

4E. Energy Transformations
  • 6-8: 4E/M2. Energy can be transferred from one system to another (or from a system to its environment) in different ways: 1) thermally, when a warmer object is in contact with a cooler one; 2) mechanically, when two objects push or pull on each other over a distance; 3) electrically, when an electrical source such as a battery or generator is connected in a complete circuit to an electrical device; or 4) by electromagnetic waves.
4F. Motion
  • 3-5: 4F/E1a. Changes in speed or direction of motion are caused by forces.
  • 3-5: 4F/E1bc. The greater the force is, the greater the change in motion will be. The more massive an object is, the less effect a given force will have.
  • 6-8: 4F/M3a. An unbalanced force acting on an object changes its speed or direction of motion, or both.
  • 9-12: 4F/H1. The change in motion (direction or speed) of an object is proportional to the applied force and inversely proportional to the mass.
  • 9-12: 4F/H4. Whenever one thing exerts a force on another, an equal amount of force is exerted back on it.

11. Common Themes

11B. Models
  • 6-8: 11B/M4. Simulations are often useful in modeling events and processes.
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Record Link
AIP Format
(PhET, Boulder, 2017), WWW Document, (
PhET Simulation: Gravity and Orbits, (PhET, Boulder, 2017), <>.
APA Format
PhET Simulation: Gravity and Orbits. (2017, August 15). Retrieved August 7, 2020, from PhET:
Chicago Format
PhET. PhET Simulation: Gravity and Orbits. Boulder: PhET, August 15, 2017. (accessed 7 August 2020).
MLA Format
PhET Simulation: Gravity and Orbits. Boulder: PhET, 2017. 15 Aug. 2017. 7 Aug. 2020 <>.
BibTeX Export Format
@misc{ Title = {PhET Simulation: Gravity and Orbits}, Publisher = {PhET}, Volume = {2020}, Number = {7 August 2020}, Month = {August 15, 2017}, Year = {2017} }
Refer Export Format

%T PhET Simulation: Gravity and Orbits
%D August 15, 2017
%C Boulder
%O text/html

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%0 Electronic Source
%D August 15, 2017
%T PhET Simulation: Gravity and Orbits
%V 2020
%N 7 August 2020
%8 August 15, 2017
%9 text/html

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