MS-ESS1-2: Gravity holds the solar system and the galaxy together
What students must show for performance expectation MS-ESS1-2, with a lesson sequence built on live data, the misconceptions to expect, and assessment questions with answers.
Last updated . Curriculum links last reviewed November 2026.
What students must show
Our summary- Students develop and use a model to describe the role of gravity in the motions within the solar system and within galaxies.
Gravity as the force that holds the solar system and the Milky Way together and controls orbits. Models can be physical (orbit visualizations) or conceptual (scale proportions).
Kepler's laws, and the way planets sometimes seem to move backward across the sky.
Our summary, in our own words. Read the official wording.
The three dimensions
Middle schoolDeveloping and using models
Develop and use a model to describe phenomena.
ESS1.A and ESS1.B
The solar system is part of the Milky Way, one of many galaxies; the Sun's gravity holds the planets, moons and asteroids in orbit.
Systems and system models
Models can represent systems and their interactions.
Live tools for this standard
3 toolsLesson sequence
Engage to evaluate- Engage10 min
Open the Live Globe: thousands of satellites going round Earth. Ask: what stops them flying off into space? What stops them falling?
- Explore25 min
Outdoors, swing a soft ball on a string and let go: it flies off in a straight line. Indoors, roll marbles across a stretched sheet with a heavy ball in the middle: they curve and circle. What makes an orbit tighter or wider?
- Explain20 min
Deep Space map: the inner planets move fastest. The Sun holds the planets, the planets hold their moons, and the whole Milky Way holds the Sun, which takes about 230 million years to go round the galaxy once.
- Evaluate15 min
Students draw a system model with arrows for Sun and planet, planet and moon, and galaxy center and Sun, and label what gravity does in each.
Common misconceptions
3 to watch forGravity stops at the edge of the atmosphere.
Gravity reaches across space: it holds the Moon and the planets in their orbits.
Ask: what keeps the Moon from drifting away?
Things in orbit need a push to keep going.
In space there is almost nothing to slow them, so they keep moving; gravity only bends the path.
The marble on the sheet keeps rolling without a push.
The Sun is at the center of the galaxy.
The Sun is one of hundreds of billions of stars, about 26,000 light-years from the center of the Milky Way.
Show a telescope picture of a spiral galaxy and mark roughly where we would be.
Assessment questions
Answers folded awayMS-ESS1-2: Gravity holds the solar system and the galaxy together · orbitalradar.com/schools/us/standards/ms-ess1-2
- What keeps the Moon in orbit around Earth?
- Earth's magnetism
- Earth's gravity
- The Sun's light
- Which planet goes round the Sun fastest?
- Mercury
- Earth
- Neptune
- If the Sun's gravity switched off, what would Earth do?
- Name one system held together by gravity that is bigger than the solar system.
- Claim, evidence, reasoning: does a spacecraft far from the Sun still feel the Sun's gravity? Use the Deep Space map.
Answer key
- Earth's gravity.
- Mercury, the closest.
- Carry on in a straight line at its current speed.
- The Milky Way galaxy, or a cluster of galaxies.
- Yes: its path still curves around the Sun. Gravity weakens with distance but never reaches zero.
Worksheet
US LetterNo live-data worksheet for this standard yet: print the assessment questions above. Kepler's laws are outside this standard, so the Kepler sheet is high school work. All sheets: the worksheet library.
The same idea in state standards
Texas, Florida, Georgia- Texas: 7.9B
- Florida: SC.8.E.5.4
- Georgia: S6E1.d
Related, not equivalent: each state words and groups its standards differently.
More standards pages
Middle schoolAbout these codes
These are our suggestions for where each tool fits. Always preview a page before using it with a class: some tools show ads, these school pages do not.
Codes are performance expectations of the Next Generation Science Standards*, for example 5-ESS1-2. Each summary is our own wording; follow the link on a standard page for the official text.
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Cite this page
Pick a style, then copy it or download it for your reference manager.Orbital Radar. (2026, November 6). MS-ESS1-2: Gravity holds the solar system and the galaxy together. Retrieved November 6, 2026, from https://orbitalradar.com/schools/us/standards/ms-ess1-2
“MS-ESS1-2: Gravity holds the solar system and the galaxy together.” Orbital Radar, 6 Nov. 2026, orbitalradar.com/schools/us/standards/ms-ess1-2. Accessed 6 Nov. 2026.
Orbital Radar (2026) MS-ESS1-2: Gravity holds the solar system and the galaxy together. Available at: https://orbitalradar.com/schools/us/standards/ms-ess1-2 (Accessed: 6 November 2026).
Orbital Radar. “MS-ESS1-2: Gravity holds the solar system and the galaxy together.” Last modified November 6, 2026. https://orbitalradar.com/schools/us/standards/ms-ess1-2.
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* Next Generation Science Standards is a registered trademark of WestEd. Neither WestEd nor the lead states and partners that developed the Next Generation Science Standards were involved in the production of this product, and do not endorse it.