• 3-5: 4A/E4. The earth is one of several planets that orbit the sun, and the moon orbits around the earth.
• 6-8: 4A/M3. Nine planets of very different size, composition, and surface features move around the sun in nearly circular orbits. Some planets have a variety of moons and even flat rings of rock and ice particles orbiting around them. Some of these planets and moons show evidence of geologic activity. The earth is orbited by one moon, many artificial satellites, and debris.

• 6-8: 4B/M2ab. The earth is mostly rock. Three-fourths of the earth's surface is covered by a relatively thin layer of water (some of it frozen), and the entire planet is surrounded by a relatively thin layer of air.
• 6-8: 4B/M2cd. Earth is the only body in the solar system that appears able to support life. The other planets have compositions and conditions very different from the earth's.

• 6-8: 4F/M3b. If a force acts towards a single center, the object's path may curve into an orbit around the center.

• 6-8: 4G/M2. The sun's gravitational pull holds the earth and other planets in their orbits, just as the planets' gravitational pull keeps their moons in orbit around them.

• 3-5: 11B/E4. Models are very useful for communicating ideas about objects, events, and processes. When using a model to communicate about something, it is important to keep in mind how it is different from the thing being modeled.
• 6-8: 11B/M1. Models are often used to think about processes that happen too slowly, too quickly, or on too small a scale to observe directly. They are also used for processes that are too vast, too complex, or too dangerous to study.

• 6-8: 11D/M3. Natural phenomena often involve sizes, durations, and speeds that are extremely small or extremely large. These phenomena may be difficult to appreciate because they involve magnitudes far outside human experience.

• 3-5: 12B/E3. Judge whether measurements and computations of quantities such as length, weight, or time are reasonable by comparing them to familiar values.
• 6-8: 12B/M5. Estimate distances and travel times from maps and the actual size of objects from scale drawings.

• 6.RP.3.a Make tables of equivalent ratios relating quantities with whole number measurements, find missing values in the tables, and plot the pairs of values on the coordinate plane. Use tables to compare ratios.
• 6.RP.3.d Use ratio reasoning to convert measurement units; manipulate and transform units appropriately when multiplying or dividing quantities.

• 6.EE.7 Solve real-world and mathematical problems by writing and solving equations of the form x + p = q and px = q for cases in which p, q and x are all nonnegative rational numbers.

• 7.EE.4.a Solve word problems leading to equations of the form px + q = r and p(x + q) = r, where p, q, and r are specific rational numbers. Solve equations of these forms fluently. Compare an algebraic solution to an arithmetic solution, identifying the sequence of the operations used in each approach.

Wonderful set of four lessons that explore scale, relative sizes, and composition or the planets in our solar system. Kids will work with physical models to understand size and orbital distance in a fun, memorable way. Can be adapted for 5th graders, yet also includes extension mathematics for Grades 7-8, such as calculating planet density. We recommend teaming these hands-on activities with the PhET Solar System Simulator (see Activities below).

• Physical Sciences K-8 Astronomy Resources for the K-8 Classroom Unit