Unit 04 · The Solar System
This unit is the tour of our own neighborhood. It contrasts the small rocky terrestrial planets with the gas and ice giants, sorts the moons, asteroids, comets, and Kuiper belt into place, and explains the orbital motion that keeps them running — Kepler's laws and gravity together, ellipses rather than circles, faster near the Sun and slower far out. You'll build or interpret a scale model, an orrery, to feel the true distances, and trace the whole system back to the collapsing solar nebula that sorted rock inward and gas outward. Mastery means you can explain not just what orbits the Sun but why it moves the way it does.
| Criterion | Not yet | Approaching | Mastered |
|---|---|---|---|
| Terrestrial vs. giant planets & small bodies | Cannot distinguish planet types or name the small bodies. | Sorts planets loosely but muddles moons, asteroids, comets, and the Kuiper belt. | Contrasts terrestrial with gas and ice-giant planets and places moons, asteroids, comets, and the Kuiper belt. |
| Orbital motion (Kepler & gravity) | Thinks orbits are circles traveled at constant speed. | Says an orbit is an ellipse but cannot link it to gravity or changing speed. | Uses Kepler's laws and gravity to explain elliptical orbits and why a planet speeds up near the Sun. |
| Scale model & the orrery | Has no sense of the solar system's true scale. | Builds a model but ignores relative sizes and distances. | Builds or interprets a scale model — an orrery — that honors relative sizes and distances. |
| Formation from the solar nebula | Cannot say how the system formed. | Names “a cloud of gas” but not the sorting by distance. | Explains formation from the collapsing solar nebula and why rocky worlds lie inside and giants outside. |
| Observation technique & the journal | Cannot find a planet in the sky and leaves the journal blank. | Spots a planet but keeps thin, undated notes. | Locates planets and the Moon with binoculars, telescope, and star charts and logs their motion across weeks in a dated journal. |
| Integration (cross-domain) | Treats the science as isolated facts; makes no cross-domain connection. | Names a link to history, reading, or writing but cannot defend why it matters. | Connects the unit to its anchor across History · Reading · Writing (plus chosen electives) and defends why the connection matters. |
“The inner worlds are small and rocky, the outer ones huge and gassy, because the young Sun’s heat let only metal and rock condense close in. Planets orbit in ellipses and speed up near the Sun — Kepler and gravity, not magic. I’ve watched Jupiter drift against the stars week to week in my journal.”
“There are eight planets and some space rocks. They go around the Sun in circles. They formed somehow.”
You demonstrate this unit by building or interpreting a scale model of the solar system and tracking a planet’s motion in your dated sky journal, explaining orbital motion and formation aloud — not a multiple-choice test. A criterion counts as mastered only when your model honors real scale and you can justify the physics behind the orbits. Mastery is demonstrated, not awarded.
A 5-page clipboard packet — unit overview, key terms, the mastery rubric, anchor examples, and a score sheet you can print and grade against.