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Earth and Space 6-8 / Week 12 / Thursday
4/6
Week 12 · Design a Solar System Model

Thursday

Improve the design
// Criteria, constraints, build, measure, improve
⏱ about 20 min

Thursday: Improve the Design

Rocket studies the test table. "Mars was four centimeters off. Uranus was seven. Everything else was close."

"What do you notice about the two that were off?" Raven asks. "Both measured after the string was bumped."

"So I re-lay the string and measure each one from the Sun again," Rocket says. "Fix one: better measuring."

Nova hovers over the row of identical bottle caps. "And your sizes?" she asks. "The caps are all alike."

Raven opens the fact sheet. "Jupiter is eleven Earths across. We could draw size circles on the labels, at a second scale."

"Two scales, clearly labeled," Rocket says. Nova hums. "Honest models say what they show."

Read the sizes from NASA

NASA's Planetary Fact Sheet gives each planet's diameter. Jupiter is 142,984 kilometers across and Earth is 12,756.

Divide and you find Jupiter is about 11 Earths across. OpenStax Astronomy says about 1,300 Earths could fit inside Jupiter.

Mercury, at 4,879 kilometers, is the smallest planet. Neptune is 49,528 kilometers, about four Earths across.

Sizes need their own scale. One idea: draw each planet as a circle on its label at 1 millimeter for every 2,000 kilometers.

PlanetDiameter (km) from NASAEarths across (rounded)Circle on the label at 1 mm per 2,000 km
Mercury4,879less than halfabout 2 mm
Venus12,104about 1about 6 mm
Earth12,7561about 6 mm
Mars6,792about halfabout 3 mm
Jupiter142,984about 11about 71 mm
Saturn120,536about 9about 60 mm
Uranus51,118about 4about 26 mm
Neptune49,528about 4about 25 mm
USE THE SIZE TABLE
  • Read the question.
  • Tap your answer.
About how many Earths fit across Jupiter?
Which planet is the smallest?
Why do sizes need a second scale in a hallway model?

Improve, then retest

The standards describe an iterative process: test the most promising solution, modify it from the results, and test again.

Pick the two biggest problems from your test table. Decide one change for each. Make the changes, then measure every marker from the Sun again.

Common improvements: re-lay the string straight, measure each planet from the Sun rather than from the last planet, and write bigger labels.

Keep your first test table. Your report will compare the first test and the second.

  1. Write the two biggest problems from Wednesday in your Sky Log.
  2. Write one change for each problem and why you expect it to help.
  3. Make the changes. Re-lay the string and reposition any marker that was off.
  4. Add a size circle to each label using the table, or another clear way to show size.
  5. Measure all eight markers from the Sun again and fill a second test table.
  6. Compare the two tables. Did every difference shrink? Write what still needs work.
Jupiter's diameter is 142,984 km, about ____ Earths across.
The smallest planet in the table is ____.
StatementTrue or false?
Improving a design means changing it based on test results, then testing again.?
Jupiter is about 1,300 times the volume of Earth, according to OpenStax.?
Neptune is about 11 Earths across.?
A second, labeled scale for sizes is an honest way to show them.?
WHY THIS EXERCISEAnalyzing the size data and improving from test data are both parts of the standards this week.
Try it
Walk your improved model from the Sun to Neptune and say each planet's name and its Earths-across number.
Ask a family member to find Earth without help. If they cannot, your labels need another improvement.
Draw your eight labels with their size circles to the 1 millimeter per 2,000 kilometer scale. Jupiter needs the most room.

Improved and retested. Tomorrow you write the Earth and Space report that gathers all twelve weeks.

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