Students who demonstrate understanding can: Develop and use a model of the Earth-sun-moon system to describe the cyclic patterns of lunar phases, eclipses of the sun and moon, and seasons.
Clarification statement: Examples of models can be physical, graphical, or conceptual.
Official wording from the Next Generation Science Standards (NGSS Lead States, 2013). NGSS is a registered trademark of WestEd. Neither WestEd nor the lead states and partners that developed the NGSS were involved in the production of this page, and they do not endorse it. View on nextgenscience.org
Three repeating sky patterns that every student has noticed, the changing shape of the moon, the rare darkening of the sun or moon, and the march of summer and winter, all come from the positions and motions of just three bodies. Middle schoolers build a model (a lamp and ball in a dark room, a labeled diagram or a computer simulation) and use it to explain each pattern, rather than memorizing a list of facts.
Phases happen because half of the moon is always lit by the sun, and as the moon orbits Earth over about a month we see different fractions of that lit half. Eclipses happen only when the sun, Earth and moon line up closely; because the moon's orbit is tilted about 5 degrees compared with Earth's orbit, that lineup does not happen every month. Seasons come from the 23.5 degree tilt of Earth's axis, which changes how directly sunlight strikes each hemisphere and how many hours of daylight it gets across the year. Distance from the sun is not the cause.
A strong model makes predictions: if students can position the three bodies to show a full moon, a lunar eclipse and June in the Southern Hemisphere, they understand the system.
Many students think the dark part of the moon is Earth's shadow. Earth's shadow only falls on the moon during a lunar eclipse; phases come from our changing view of the moon's sunlit half.
Earth is actually closest to the sun in early January, during Northern Hemisphere winter. Ask why Australia has summer in December if distance were the cause.
Students who picture all three bodies in one flat plane expect monthly eclipses. A tilted hoop or a hula hoop model shows the moon usually passes above or below the shadow.
The moon reflects sunlight. If the lamp in a classroom model is switched off, the ball cannot be seen at all, which makes the point quickly.
A student says, "At full moon the Earth is between the sun and moon, so there should be a lunar eclipse every month." Use the Earth-sun-moon model to explain what is wrong.
Answer: Because the moon's orbit is tilted, the moon normally misses Earth's shadow at full moon; an eclipse only happens when full moon falls where the two orbital planes cross.
A darkened room, one bright bulb and a foam ball on a pencil remain the most powerful model here. Have students hold the ball at arm's length and turn slowly, naming each phase as it appears; then tilt the orbit to explore eclipses. For seasons, a globe with a fixed tilt walked around a lamp lets students measure how a flashlight beam spreads out on a surface tilted away from it.
Assessment items often show a diagram of the three bodies and ask students to predict the phase seen from Earth, or present a claim about seasons and ask for evidence that refutes it.
Original questions written for this standard. Choose an option or type your answer, then press Check. Every question has a worked explanation.
Answer: B) Our changing view of the moon's sunlit half as it orbits Earth
Half of the moon is always lit. As it orbits Earth we see more or less of that lit half, which produces the phases.
Answer: C) New moon
A solar eclipse needs the moon between the sun and Earth, which is the new moon position.
Answer: D) The tilt of Earth's axis
The 23.5 degree tilt changes how directly sunlight hits each hemisphere and the length of daylight across the year.
Answer: full moon (also accepted: full)
Earth must be between the sun and moon, which only happens at full moon.
Answer: B) Winter
When the Northern Hemisphere tilts toward the sun, the Southern Hemisphere tilts away and has winter.
Answer: 29.5 (also accepted: 29.5 days, about 29.5 days, 29, 30)
The cycle from one new moon to the next takes about 29.5 days.
Use observations of the sun, moon, and stars to describe patterns that can be predicted.
Use mathematical or computational representations to predict the motion of orbiting objects in the solar system.
A full lesson with slides, activities and an exit ticket on moon phases, eclipses and seasons, pitched to grades 6-8 and editable in PowerPoint or Google Slides.
Make a lesson βA printable, differentiated worksheet on MS-ESS1-1 with an answer key, ready in about a minute.
Make a worksheet βTurn moon phases, eclipses and seasons into a quiz students answer online that marks itself, with a class summary for you.
Build a test βThe focus is on using a model to explain the cyclic patterns. Naming the main phases helps students talk about the model, but the explanation is what matters.
The clarification statement allows physical, graphical or conceptual models, so a lamp and ball, a labeled diagram or a simulation can all work.