Formative Assessment: Sun, Earth, and the Moon

🧠 Big Ideas and Big Questions

• Why do we have seasons?
• Is the Earth or the Sun at the center of the Solar System?
• How do the Sun, Earth, and Moon interact?
• How can the Sun’s position create shadows, eclipses, and equinoxes?
• How do these interactions affect what we see from Earth?

💭 Reflections and Additional Resources

• Formative Assessment: Sun, Earth, and the Moon
• Explore: Where are the Moon, Sun, and Earth compared to each other for the different Moon phases?

📚 Vocabulary

• Heliocentrism: The theory that the Sun is at the center of the solar system.
• Geocentrism: The theory that Earth is at the center of the solar system.
• Equinox: The day when there is an equal amount of day and night (12 hours each).
• Solstice: The day with the most or least sunlight in a year.
• Eclipse: When light from the Sun or Moon is blocked by another object.

Seasons

Earth’s axis is tilted, so different areas are tilted toward the Sun at different times of year, causing seasons.

• If a hemisphere is tilted toward the Sun, it’s summer there.
• If a hemisphere is tilted away, it’s winter.

Earth orbits in the same plane as the other planets in our solar system: the Plane of the Ecliptic. However, Earth is also tilted on its axis. This tilt never changes in relation to space, so different areas of Earth are tilted toward the Sun at different times of year. This is why we have seasons.

• If a hemisphere is tilted towards the Sun, it gets more sunlight and it warms up–aka summer.
• If a hemisphere is tilted away from the Sun, it gets less sunlight and it cools down–aka winter.

Additionally, the Northern and Southern Hemispheres have opposite seasons due to the tilt of Earth’s axis. When the Northern Hemisphere is tilted towards the Sun, it is summer (this is winter in the Southern Hemisphere). When the Southern Hemisphere is tilted towards the Sun, it is summer (this is winter in the Northern Hemisphere).

Earth’s seasons are explained in the image below.

Image: Seasons by NASA Space Place (public domain)

Heliocentrism vs Geocentrism

In early times, humans believed in geocentrism–the theory that Earth is at the center of the solar system, and the Sun and other planets revolved around it. During the Renaissance in the 1500s, Copernicus popularized the concept of heliocentrism–the theory that the Sun is at the center of the universe and Earth orbits the Sun. Galileo’s observations with the telescope disproved the geocentric model, but the Catholic Church resisted this idea for many years.

Throughout Copernicus’s lifetime, the scientific community widely denied the theory of heliocentrism. A generation later, the Sun-centered theory became more commonly accepted when Galileo invented the telescope in 1609, making it easier to observe space. Additionally, Galileo made a variety of discoveries about our solar system that disproved the geocentric model of the universe. Despite these discoveries, however, there was still significant pushback against heliocentrism, particularly from the Catholic Church.

At the time, the Church defended its stance on geocentrism because it believed Galileo’s discoveries left too many questions unanswered and did not explicitly prove heliocentrism. During this period, a case could still technically be made for geocentrism until technology advanced enough for scientists to discover more evidence supporting heliocentrism.

Additionally, the Church had certain clergy who interpreted parts of the Bible very literally, as if it were a science textbook rather than a theological work. Galileo’s claims were scandalous in their eyes because heliocentrism directly conflicted with certain biblical passages. For these reasons, the Church put Galileo on trial, convicted him of heresy, and sentenced him to house arrest for the remainder of his life. In 1822, the Church eventually accepted the theory of heliocentrism once there was enough scientific evidence to claim it as truth. Finally, in 1992, the Catholic Church, after a 13-year investigation by Pope John Paul II, formally acknowledged that Galileo was unfairly prosecuted. LINK

Equinox & Solstice

• Equinoxes (Spring & Autumn): All of Earth receives equal sunlight—12 hours. It occurs when the Equator is directly in line with the Sun (around March 20 and September 23).
• Solstices (Winter & Summer): Mark the shortest and longest days of the year.
  • Winter Solstice: Least sunlight (around December 21).
  • Summer Solstice: Most sunlight (around June 21).

Solstices mark the days of the year in which a hemisphere receives the least amount of sunlight (aka the shortest day of the year) and the most amount of sunlight (aka the longest day of the year). These days occur when one of the tropic lines is directly in line with the Sun. In the Northern Hemisphere, the Winter Solstice (the day with the least sunlight, usually around December 21) occurs when the Tropic of Capricorn (the southern tropic line) is in line with the Sun. The Summer Solstice (the day with the most sunlight, usually around June 21) occurs when the Tropic of Cancer (the northern tropic line) is in line with the Sun.

Images: Equinox and Solstice by Przemyslaw “Blueshade” Idzkiewicz (CC BY SA-2.0)

Shadows

As Earth orbits the Sun, the length and direction of shadows change.

• During the Summer Solstice in the Southern Hemisphere, if you are standing on the Tropic of Capricorn at noon, your shadow points directly beneath you.
• In Iowa, as we approach the Spring Equinox, shadows become shorter.

Eclipses

• Solar Eclipse: The Sun is blocked when the Moon passes between Earth and the Sun (occurs during a new moon).
• Lunar Eclipse: The Moon is blocked when it passes through Earth’s shadow (occurs during a full moon).

Solar Eclipse

• In a solar eclipse, the Sun is blocked–this happens when the Moon perfectly crosses between Earth and the Sun. A solar eclipse always occurs during a new moon.

For more explanation of solar eclipses, watch the video below:

Video credit: “What Creates a Total Solar Eclipse?” by Andy Cohen/TED-Ed is licensed under CC BY-NC-ND 4.0

Lunar Eclipse

• In a lunar eclipse, the Moon is blocked when it passes through Earth’s shadow. When the Moon is in this position, the Sun’s light cannot reach it. A lunar eclipse always occurs during a full moon.

For more explanation of lunar eclipses, watch the video below:

Video credit: “Lunar Eclipse Essentials” by NASA is public domain

Images: Total Solar Eclipse by NASA; Lunar Eclipse by NASA’s Marshall Space Flight Center (CC BY-NC 2.0)Key Takeaways

👩‍🏫 Teacher Talk

• This lesson aligns with NGSS 1-ESS1-1: Use observations of the sun, moon, and stars to describe patterns that can be predicted.
• NGSS 1-ESS1-2: Make observations to relate the amount of daylight to the time of year.
• NGSS 5-ESS1-2: Represent data in graphical displays to reveal patterns of daily changes in length and direction of shadows, day and night, and the seasonal appearance of some stars.

📎 Resources

• Moon Phases from Earth (Image)
• The Moon (Khan Academy Video)
• Total Solar Eclipse (NASA)
• Lunar Eclipse (NASA)
• Seasons (NASA Space Place)

Performance Expectations

Disciplinary Core Ideas: DCI

First grade: ESS1.B: Earth and the Solar System

• Seasonal patterns of sunrise and sunset can be observed, described, and predicted. (1-ESS1-2)

Fifth grade: ESS1.B: Earth and the Solar System

• The orbits of Earth around the sun and of the moon around Earth, together with the rotation of Earth about an axis between its North and South poles, cause observable patterns. These include day and night; daily changes in the length and direction of shadows; and different positions of the sun, moon, and stars at different times of the day, month, and year. (5-ESS1-2)

Middle School

This model of the solar system can explain eclipses of the sun and the moon. Earth’s spin axis is fixed in direction over the short-term but tilted relative to its orbit around the sun. The seasons are a result of that tilt and are caused by the differential intensity of sunlight on different areas of Earth across the year. (MS-ESS1-1)

Crosscutting Concepts: CCC

First grade: Patterns

• Patterns in the natural world can be observed, used to describe phenomena, and used as evidence. (1-ESS1-1),(1-ESS1-2)

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Connections to Nature of Science

Scientific Knowledge Assumes an Order and Consistency in Natural Systems

• Science assumes natural events happen today as they happened in the past. (1-ESS1-1)
• Many events are repeated. (1-ESS1-1)

Patterns

• Similarities and differences in patterns can be used to sort, classify, communicate and analyze simple rates of change for natural phenomena. (5-ESS1-2)

Cause and Effect

• Cause and effect relationships are routinely identified and used to explain change. (5-PS2-1)

Systems and System Models

• Models can be used to represent systems and their interactions. (MS-ESS1-2)

Lesson ideas:

1. Create a daily journal of sky observations: where the Sun is, what time the Sun rises and sets, and the Moon’s position. Can be part of daily calendaring. Compare to seasons.
2. Play with shadows outside and inside: shadow tag, tracing shadows with sidewalk chalk, and seeing how they move throughout the day; compare shadows to where the Sun is. Play with shadows inside: shine flashlights on sticks indoors, have kids move the flashlight up and down to see how the length of the shadow moves. Draw the shadow and write where the flashlight was.
3. Experiment with the Sun/Moon/Earth system as we did in class to understand equinoxes, solstices, eclipses, seasons, etc.