Moon Phases Worksheet
Goal: Model why the Moon’s appearance changes during a 29.5-day cycle, and name and predict the eight phases.
What to do
- Press the “New Moon” preset. In the first row of the table, record the illuminated percentage and the phase name.
- For each remaining row, type the number of days into Days since new Moon (or drag the slider). Record the illuminated percentage and the phase.
- Press Play simulation and watch a full cycle. Notice when the lit part grows (waxing) and when it shrinks (waning).
- Type today’s date into Estimate for a date and write the phase in the last row.
Record your results
| Setting | Illuminated | Phase |
|---|---|---|
| Day 0 | ||
| Day 3.7 | ||
| Day 7.38 | ||
| Day 11.1 | ||
| Day 14.77 | ||
| Day 18.5 | ||
| Day 22.15 | ||
| Day 25.8 | ||
| Today’s date: ____________ |
Questions
How many days does it take to go from one new Moon to the next? From new Moon to full Moon?
At first quarter, what percentage of the Moon’s face is lit? Why is it called a “quarter” Moon?
Days 3.7 and 25.8 have almost the same lit percentage. How are the two phases different?
Predict: tonight the Moon is at first quarter. What will the phase be in about one week? In about two weeks? Check with the slider.
Many people think the phases are caused by Earth’s shadow. Use the model to explain what really causes them.
The Moon orbits Earth in 27.3 days. Why does the cycle of phases take longer (29.5 days)?
Free from The Astronomy Lab · theastronomylab.com · MS-ESS1-1: Model the Earth–Sun–Moon system to describe lunar phases, eclipses and seasons.