Unit 1: How Big and How Far? Session Summaries (9 Sessions)

1.1 Thinking About Space
Students first practice answering questionnaire questions and then fill out the Pre-Unit 1 Questionnaire, used to assess their understanding of the relative sizes of the Sun, Earth, and Moon, distances between them, and how the apparent size of an object depends on its distance from the observer. Students will collect evidence throughout the unit, to help them come up with explanations for these questions. Then a similar, post-unit questionnaire will be administered in Session 1.9 to assess how students' ideas on these key concepts have changed. At the end of the session students read about the first "sky exploring mission" by a sheep, duck, and chicken that were sent up in a hot air balloon. They discuss how this expedition provided evidence that there was enough air at a certain altitude for animals to breathe. Students are introduced to the idea that science is a way of explaining the physical world based on all the available evidence.

1.2 What's in the Sky?
Students brainstorm a list of objects that can be seen in the night and day sky. Then they list space objects they have heard of, but that cannot be seen from Earth with the naked eye. The students make drawings of objects in the sky; in subsequent sessions these informal drawings will serve as a basis for discussions of scientific models and issues of scale. Students are introduced to the concept of a model. They consider both two dimensional models (their drawings of space objects) and three-dimensional models (a model car). They learn how astronomers find scale models useful because the objects they study are usually so big and far away and students learn to consider and describe the inaccuracies in a model.

1.3 Measuring Sizes of Objects
Students learn (or review) how to measure the size of objects and then practice measuring using metric units. As a class, they measure the wingspan of a sky object-the biggest bird (an albatross), then in teams of two they measure the wingspan of the smallest bird (a hummingbird), and of four satellites. These are the only sky objects they will measure directly; in the coming sessions, they will measure the sizes and distances of space objects using scale models.

1.4 How Big Are the Earth, Moon, and Sun?
Students review the concept of a model, and are introduced to scale models. Students go on to predict the relative sizes of the Earth, Moon, and Sun and after a review of measurement and an introduction to kilometers, students measure the diameters of Earth, Moon, and Sun models using special scale rulers in which 1 mm represents 3,000 km. They also measure how many "Earths" fit across the "Sun's" diameter. They learn that: the Moon is very big, Earth is huge, and the Sun is super huge; that our Sun is a star; and that while enormous, our Sun is just an average-sized star. A look at 3-D scale models gives them a sense of the stunning differences in size between these objects. In Session 1.5 students reflect on the data they have gathered in this session, and discuss such questions as, "Why does the Sun looks so small if it's really so big?"

1.5 Sizes Near and Far
Having gathered evidence about the actual sizes of objects in the sky, students now reconcile this information with their own observations of the apparent sizes of objects in the sky. They learn that objects in the sky that appear to be similar in size may be very different in size, but at different distances from Earth. Students collect evidence about the difference between actual and apparent size by measuring a piece of paper, and the height of a student, from up close and across the room. This evidence helps them understand why the Sun and Moon look similar in size, when in fact the Sun is much larger than the Moon.
The students then are given a data sheet with a picture of various objects in the sky and on the ground, and challenged to rank them by size. The objects have been chosen and drawn to provoke questions about how difficult it is to tell the size of objects when some are near, and some are very far. Next they meet in groups of four and take turns showing other members of the group how they think the objects should be ranked, and why. They do this by arranging a set of cards. After realizing how difficult it is to rank objects by size with little evidence, students are given more evidence to work with - the measurements of each object- and discuss how scientists use evidence. As individuals they then re-order the objects on their sheets by size. This activity is not actually an Evidence Circle, but introduces students to the format for Evidence Circles, which will be used in sessions 8 and 9, as well as in other units of the Space Science Core Sequence. In pairs, students get a chance to synthesize all this information and take turns describing to their partner how they would respond to two inaccurate statements about sizes of the Sun, Moon and stars. At the end of the session, students reflect on key concepts about the relationship between apparent size of objects and their distances from us.

1.6 Ranking Space Objects by Size
This session temporarily digresses from the focus on the Earth, Moon, and Sun and explores space objects your students likely have heard of and are curious about. The focus is still on size, allowing students to put space objects into context based on the sizes of the Earth, Moon, and Sun. They learn that there are many space objects out there that are inconceivably big. The session also helps add to their basic understanding that huge space objects may look small because they are far away. Pairs of students explore and then categorize by size, a set of cards with pictures of sky objects on them. Then the teacher leads the class in a "Tour of Sky Objects." As information about the sizes of the objects as determined by space scientists is revealed, students adjust their sorts of the sky object cards. The tour of images serves the dual purpose of revealing the actual relative sizes of the objects and provides opportunity for students to gaze in wonderment at beautiful and mysterious space images.

1.7 How Far Away Are They?
In previous sessions, the students compared the sizes of various sky objects and began to explore how distance affects their apparent size. In this session, students use models to measure how far away these sky objects are. Using a new scale ruler, student pairs circulate to stations around the classroom to measure the distance between the ground and 13 different objects - including the tallest mountain, a cloud, a hot air balloon, an airplane, satellites, the International Space Station, and the Moon. They make their measurements on scale drawings. They discuss the relative distances of all objects, including how much farther away the Moon is than any of the other objects measured. They also discuss which objects are in Earth's atmosphere and which are in space.  

1.8 Size and Distance
Students then read Jumping From the Edge of Space, the story of the first person to skydive back to Earth from "the edge of space." Students compare the relative distances of the sky objects they measured in Session 1.7. Then, in order to measure the distance to the Moon and Sun, they learn that they need to change the scale of their model. They use the Earth, Moon and Sun scale models from Session 5 again, but this time they use them to investigate the distances between the Earth, Moon, and Sun. After making predictions, they learn the distance from Earth to the highest skydive, Satellite #2, and the Moon. They compare the relative distance to the Moon with the distances of the other sky objects, and find the Moon is much farther away. The relatively small distance to the top of Earth's atmosphere is evident when contrasted with the distance to the Moon at this scale. Students go outside (or into a long hallway or large room) to pace off the distance to the Sun at this scale. By contrasting this distance with the distance to the Moon, students begin to comprehend the distance to the Sun. They learn that other objects in space are much farther away than the Sun. In Evidence Circles they discuss where the Moon would be placed on a line in relation to the Earth and Sun. 
Each evidence circle group presents their group decision to the large group. The actual answer is then revealed to the class. 

1.9 How Our Scale Ideas Have Changed
Students learn that either through magnification, getting closer with a spacecraft or a combination of the two larger photos can be taken of sky objects. Students compare a 1mm "Planet X" dot at their desk with a ~4mm dot representing Venus held by the teacher. As the teacher moves the Venus dot away, students note when the two dots appear the same size. The sizes of some objects that can be seen in the sky without telescopes: Venus, Jupiter, the Moon and Sun are shown in an image which contrasts their actual relative sizes with the sizes they appear in our sky. In Evidence Circles the students are given a variety of examples of models of the Solar System. They apply their understandings about scale as they evaluate each model for accuracy in terms of size and distance. They are given sheets with information about size and distance of each sky object to use as evidence in their discussion. Finally, to conclude the unit, the students take the Post Unit 1 questionnaire on size and distance to find out how their ideas may have changed. 

Unit 2: Earth's Shape and Gravity

2.1: Ideas About the Earth and Gravity
A questionnaire launches your students on animated discussions about the implications of the ball-shaped Earth, giving them the opportunity to examine their preconceptions and begin to comprehend the Earth's shape and gravity. Students' ideas and insights about the Earth's shape and gravity develop gradually, and they develop critical thinking skills as they struggle to apply their mental models of the Earth to real and imaginary situations. To give students time to reflect, they are not provided with the right answers to the questionnaire questions until the subsequent sessions in Unit 2.

2.2: What Shape is the Earth?
In a large group discussion, students examine two different models of the Earth: a globe and a flat-Earth model. They discuss which model best represents the shape of the Earth.

To gather visual evidence of the shape of the Earth, the class next embarks on a virtual orbit around the Earth, through photographs. They notice that from close up, the Earth looks flat, but the farther you get away from it, the easier it is to see its spherical shape. After their orbital tour, class reviews question #1 from the Unit 2 questionnaire, which addresses Earth's shape. Key concepts about the Earth's shape are posted on the concept wall.

The students then work again in small groups to respond to four (fictional) statements by people who believe the Earth is flat. Students get practice in using evidence-based arguments, and in the process, they may solidify their own and their fellow students' conceptions about the Earth. 

2.3: Gravity
The goal of this session is not for students to understand fully what gravity is. Rather, it is to give students a general sense of gravity's effects on our planet and in space, and to address some common misconceptions about gravity.

The session begins with a quick demonstration and introduction to some basic concepts about gravity. Students then look at photographic evidence of how gravity affects people on different parts of the Earth. With this evidence in mind, students revisit question #4 from the Unit 2 questionnaire, which asks what direction rocks would fall on various parts of the Earth. The concept that the gravitational pull between the Earth and rocks pulls all the rocks toward the center of the Earth leads to discussion of how we can "beat" gravity.
The students are then introduced to the procedure for small group evidence circles," in which they base their discussion on evidence. In evidence circles, students discuss and write about the effects of gravity by answering the question, "Is gravity strong or weak?" Once back in the large group they continue the discussion, sharing their evidence for each position. Key concepts about gravity are posted on the concept wall.

Students then read about the first person ever to orbit the Earth in space. They hear Yuri Gagarin's eyewitness description of the spherical Earth. They learn that although he felt weightless while in orbit, Gagarin did not escape the gravitational pull between him and Earth.

2.4: Weightlessness
The focus of this session is the idea that there are no situations in the universe in which there is no gravity, but there are situations in which we may feel weightlessness. Students are introduced to spring scales, devices used to measure the gravitational pull between an object and the Earth as weight. The concept of weightlessness is introduced, and students rotate through a series of stations. Each station features a particular situation, and students are challenged to determine if in that situation there is gravity, and if a person might feel weightlessness.

The students do a class reading about an airplane utilized to create temporary situations of weightlessness. After a discussion, a student volunteer jumps and lands with a spring scale weighing an object in hand while the class carefully observes. Students discuss how the measuring device shows temporary weightlessness, even though the gravitational pull between the object and the Earth remains in effect. Finally, they are shown footage of people experiencing weightlessness. As they watch the footage, they are reminded that the gravitational pull between the people and other objects still exist, despite the fact that the people are feeling weightless. 

2.5: Gravity and Air
Teams of two students are given two binder clips and challenged to get one of the binder clips to fall more slowly than the other, using simple provided materials. They demonstrate their inventions for the class, discussing how air resistance slows the fall of some objects. 

The teacher simultaneously drops a feather and a hammer as a demonstration. In evidence circles, students discuss why one dropped more slowly than the other, then predict what would happen if the same test were performed on the Moon. The class watches a brief film clip of an astronaut performing this test on the Moon, and discusses the results in the large group. Students are told that the question of whether there is air or gravity on the Moon will be resolved more fully in the next session.

Finally, the students revisit the story of the highest skydiver, and discuss this event in light of ideas about air and gravity. 

2.6: Gravity Beyond Earth
The session begins with a simulated mission to the Moon, as the students are shown a series of 22 images from the Apollo 11 Mission. After viewing the mission, students discuss two questions in evidence circles, backing up their answers with evidence from the Apollo 11 images or elsewhere: Is there gravity on the Moon? Is there air on the Moon? The evidence that there is indeed gravity on the Moon, but no air, is shared in a class discussion, and helps students answer the question, "Does air cause gravity?" The Apollo 11 images also serve to reinforce the concept of the spherical shape of the Earth and Moon. Key concepts about air and gravity are added to the concept wall.

To conclude Unit 2, students take the Post-Unit 2 Questionnaire to find out how their ideas may have changed since the beginning of the unit.

Unit 3: How Does the Earth Move?

Session 3.1: Spinning Earth

The unit begins with the students filling out a questionnaire on their ideas about how the Earth moves. After the questionnaires have been collected, the students share observations about how the Sun and stars appear to move in the sky. 

Next, they hear about two ancient models of the Earth that explained the apparent movement of the Sun and stars. They learn that the Greeks lived at the crossroads of trade routes. Realizing that all the stories they heard couldn't be true, the Greeks attempted to come up with scientific models that could be tested using evidence. 

An activity called Mount Nose introduces the students to the scientific model that explains the Sun's apparent movement in the sky. In this model, a light bulb at the center of the room represents the Sun, and each student's head represents the Earth. Their nose represents a mountain on Earth. Each student slowly turns to simulate the spinning of the Earth. As the Earth spins, they note the position of the Sun in the sky and time of day for a person standing on Mt. Nose. They notice that although the Sun appears to be moving around them, much as it does in the sky, it's actually the Earth itself that is spinning. The model is also used to illustrate why it is daytime on one side of the Earth while it is night on the other side.

Students are then challenged to apply their knowledge by describing the model to someone who thinks the Sun goes around the Earth. In small groups called "evidence circles," students discuss ways to explain that the Earth's spinning motion causes the apparent motion of the Sun and Stars, as well as night and day. Finally, each student writes their explanations on a student sheet which can be used as an assessment before moving on to Session 3.2.

Session 3.2: Spinning Earth and Earth in Orbit

Continuing their exposure to evidence of a spinning Earth, the students look at a image of the Earth in space, as well as a spinning globe, and notice how the Earth's sunlight and shadow and Earth's spin cause the cycle of day and night.

To further explore and apply what they have learned, groups of four do an activity called Spinning Globe. Each team has a globe with four colored dots affixed to four locations along the equator. Each student represents one of these four locations. They spin the globe until the teacher says to stop. Each student then determines whether it is noon, midnight, sunrise, or sunset at their location.

Next, the Mount Nose model of the Earth and Sun is used again, but as a demonstration using only one student to model Earth's orbit around the Sun along with the Earth's spin. Students learn that it takes one year for Earth to orbit the Sun and there are 365 days in a year. The terms rotation and revolution are introduced.

Students take the Post-Unit 3 Questionnaire: How Does the Earth Move? This allows the teacher to assess how their ideas about Earth's motion have changed.

Unit 4: Moon Phases and Eclipses

Session 4.1: Observing the Moon
The session begins with the students filling out the Pre-Unit 4 Questionnaire to find out their ideas about both phases and eclipses. Students then learn a way to measure the Moon's position in the sky relative to the Sun using their fists. On three to six days during a ten day period, students go outside to observe and measure the Moon's position and shape. Through their observations, students notice a pattern that prepares them to understand the model for Moon phases that will be introduced in Session 4.2.

If direct Moon observations are not possible, you can use the Powerpoint file for Simulated Moon Phase Observations.

Session 4.2: Moon Phases
In this session, your students first review the Moon observations they have made, as well as the concepts of orbit and models. They then use a model to explain the Moon's monthly cycle of phases. The students' head will represent the Earth. They hold "moon balls" in their outstretched hands and slowly move them in circles around their heads. With a single lamp, the "Sun," lighting up each student's "Moon," the students are able to observe moon phases. They will then be able to relate this simple model to their earlier observations of the real Moon and Sun in Session 1, "Observing the Moon." They learn that one Moon orbit takes about a month, and how that has influenced the way many cultures have marked time over the ages.

Because some students may need more experience accept that it is not the Earth's shadow that is causing the Moon's phases, the class does a short "Shadow Play" activity to explore the Earth's shadow. In teams of two, they take turns being the Earth and exploring the shadows cast by their partner's Earth (head). They record their observations on a Shadow Play sheet. As students share their observations with the class, they learn that shadows are the absence of light, and that shadows can be thought about as made up of three parts:

* the shadow cast by an object onto other surfaces.
* the shadow an object casts upon itself. The dark side of the object. 
* the "invisible" shadow cast to the dark side of an object.

Session 4.3: Eclipses
So, before moving on to model lunar and solar eclipses, students gather a bit more evidence to support the scientific model of Moon phases.

They begin by predicting the shape of several mystery objects placed by the teacher on the overhead projector. They learn that an object's shadow can provide evidence of the shape of an object (although it's difficult to determine whether the object is two- or three-dimensional).

Next, they look at pictures of the Moon in two different phases, crescent and "half-moon." They notice that if a person were to look at a crescent Moon, they might conclude that Earth's curved shadow is causing the Moon's shape to look that way. But if a person examines the shape of the half-moon phase, they will notice evidence that contradicts that idea: They know that a round Earth could not be making a straight-edged shadow on the Moon. 

Having established that Moon phases are not caused by Earth's shadow, students now focus on celestial events that are caused by Earth's shadow: eclipses. Returning to the moonball model, they gather around a light bulb to simulate an eclipse of the Moon. The model also shows why lunar eclipses can occur only during the Moon's full phase, when the Earth is between the Sun and Moon.

Finally, students simulate an eclipse of the Sun. They learn that Solar eclipses occur when the Moon is between the Sun and Earth. They also learn that an eclipse of the Sun can only be seen by people who are on the part of the Earth that is in the shadow of the Moon.

Session 4.4: Impossible Missions
The final session in the grades 3-5 Space Science Core Curriculum Sequence gives students a chance to review and apply concepts they have learned in Unit 4, and throughout the entire sequence. In the Impossible Missions activity, the class is encounters three "impossible" missions to the Moon and the Sun. Each statement contains inaccuracies which should be apparent to students who have a good grasp of the concepts addressed in Unit 4. Students work in evidence circles of four students, to discuss what's wrong with each statement and record their explanations on a student sheet. The discussion and writing provides them with an opportunity to review concepts. It also provides opportunity for students to reconsider some of the misconceptions they may continue to hold. 

Teachers whose classes have experienced more than one unit in the Space Science Sequence may select additional Impossible Missions, and thereby encourage students to revisit the concepts in all four units of the sequence.

At the end of Session 4.4, students re-take the Post-Unit 4 Questionnaire: Why do we have Moon phases and eclipses? to assess how their ideas may have changed.