Learning phonics is foundational for learning to read. But, I bet you enjoyed books with your kids long before they had all the rules of phonics mastered. Learning about short vowels, consonant blends, and “silent e” helps kids become powerful readers, but the skills on their own are meaningless.

The same is true of math. Kids absolutely need to learn to add, subtract, multiply, and divide. They need to master the basic facts and learn how to convert decimals, fractions, and percentages. But their math work has little meaning unless they have a chance to see how it fits into the bigger picture.

Helping kids see the meaning and beauty of math doesn’t have to be complicated, though. Often, it’s just a matter of paying attention to numbers in daily life and in contexts outside the math book. At my house, my kids do their daily skill work in their math books, but I’m always on the lookout for ways to “talk math” outside of the math lesson.

This past week, my history and science programs happened to converge on astronomy—and provided an excellent opportunity to incorporate some math. As my kids built a scale model of the planets, they integrated Copernicus’ theory of the planets, beginning proportional reasoning, and astronomy, all in one fascinating Together Time.

Here’s what we did, with step-by-step directions if you’d like to try this activity with your kids.

### Quick Prep

Find a ruler that shows centimeters and millimeters. Print out this chart or write the target size for each planet on a sticky note. (The chart is modified from this lesson plan.) The measurements are scaled so that the planets will have the correct sizes relative to each other. (Of course, Pluto’s now classified as a dwarf planet, but we included it anyway.)

Diameter | |

Sun | 69.5 cm |

Mercury | 2.5 mm |

Venus | 6 mm |

Earth | 6.5 mm |

Mars | 3.5 mm |

Jupiter | 7.1 cm |

Saturn | 6 cm |

Uranus | 2.6 cm |

Neptune | 2.5 cm |

Pluto | 1 mm |

### Step 1: Connect to history.

(Optional—we just happened to be on this chapter, so it was fun to make the connection.) Read about Copernicus in The Story of the World, Volume 2, p. 334-338. Answer the questions from the Activity Book or simply discuss the passage.

### Step 2: Discuss scale models.

Explain that you’re going to create a *scale model* of the planets. This idea was brand new to my kindergartner, so we spent a bit of time talking about familiar examples of scale models: dollhouses, maps, Lego creations, etc. We also compared our heights and made a quick scale model of the three of us out of snap cubes.

### Step 3: Discuss metric measurement.

Part of the beauty of one-room-schoolhouse activities like this is that older kids get a chance to review more basic skills, and little ones get a preview of higher-level skills. Get out a ruler that shows centimeters, look at the chart together, and talk about the measurements, at whatever level is appropriate for your kids. Some of the things my kids and I discussed:

- Where is a centimeter on the ruler? A millimeter? How many millimeters are in a centimeter? (10 millimeters equal 1 centimeter)
- Can you show me a centimeter with your fingers? How about a millimeter? (Showing a centimeter by holding their fingers about half an inch apart helps kids develop a rough idea of how big they are. My kids also love the challenge of putting their fingers “as close together as you can without touching” to show a millimeter.)
- Which is the biggest? Which is the smallest?
- If Venus is 6 millimeters and Saturn is 6 centimeters, which is bigger? Why?
- What do the decimals mean in 7.1 cm, 2.6 cm, or 2.5 cm? (They stand for one-tenth of a centimeter, or a millimeter.) Which is bigger: 2.6 cm or 2.5 cm? Do you think we’ll be able to tell the difference between 6 mm and 6.5 mm?
- How do you measure a ball with a ruler? What is a diameter? (We practiced placing the ruler on
*top*of the ball so that it measured the diameter of the ball.)

### Step 4: Find objects that match the measurements.

Send your kids off with a ruler and the list to find round objects as close as possible to each measurement. (Or, give your kids a sticky note with a measurement on it and have them find an object to match. I did it this way so my kids could focus on one measurement at a time.) I thought we’d have to make some of the balls out of clay, but apparently we have enough spices and random kid stuff in our house that we were able to find matches for all the measurements.

Here’s our full list:

Sun | Exercise ball. (Our is a little too small, but the best we could do.) |

Mercury | Peppercorn |

Venus | Bead |

Earth | Bead |

Mars | Peppercorn |

Jupiter | Ball |

Saturn | Ball |

Uranus | Bottle cap |

Neptune | Bouncy ball |

Pluto | Cumin seed. |

### Step 5: Line up the model planets in order and marvel.

It’s pretty amazing to see how vast the sun is compared to all the planets and how widely the planets vary in size. We also talked about how far the planets are from each other. Based on these sizes, Mercury would be about 94 feet from the sun—and Pluto would be nearly 2 miles away!

### Conclusion

Whether or not you’re studying astronomy, look for opportunities to integrate math into your family’s other studies. It not only helps your kids see the bigger picture of their math studies, but it also helps them develop a positive attitude towards math. Plus, it’s a ton of fun–which we can all use this time of year!

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