XII. Making Connections to Educational Policies

B. Reflecting upon watching the sky

Nothing needs to be bought or assembled to engage children anywhere on Earth in learning about the Earth’s Moon. All one needs is the time and intention to look up at the sky whenever the Moon is visible. A class field trip to the school’s playground, a brief conversation while the children line up to come in from  recess, a greeting as students enter or leave the building all are venues within which one can teach about the Moon and its relation to the Sun when both are visible in the sky during school hours. Also engaging families in watching the Moon together at home can be an effective way to establish a positive home/school connection. It is important, however, to warn students and their families to protect their eyes by never looking directly at the Sun!

Students observed and developed understandings about the Moon and the Sun throughout the course. They began by responding to diagnostic questions that recorded their initial ideas about why it gets dark at night, why it is cold in the winter and hot in the summer, and why the moon seems to have different shapes at different times. They also recorded observations of the Moon and the Sun during class and at home during the first four weeks, identified patterns in their observations, used these patterns to predict when each phase of the Moon appears to rise, transit, and set, and responded to homework and a midterm question that focused on what they had observed but did not yet ask them to explain the phenomena observed.

After the midterm, students developed explanatory models for day and night, the phases of the Moon, and the Earth’s seasons. Typically about a third of the students experience major changes in their understandings about the Sun/Earth/Moon system. These include that the dark part of the changing phases of the Moon is caused by the Moon’s own shadow rather than the shadow of the Earth and that the Earth’s seasons are caused by the tilt of the Earth’s axis as the Earth revolves around the Sun rather than by how close or far the Earth is to the Sun. When time permits, students also consider the role of gravitational forces in the Moon’s orbital motion around the Earth and in causing the Earth’s tides.

Acting out the inferred motions of the Moon around the Earth while the Earth moves around the Sun can lead to a surprising inference: when one is looking at a third quarter Moon, one is looking at the “place in space” where everyone on Earth is heading next during the Earth’s orbit around the Sun! How soon will we all get there? An estimate of about 3.5 hours emerges from using the assumption of circular orbits, relevant mathematics, and information about the distance between the Earth and the Moon as well as the distance between the Earth and the Sun! (When looking at a first quarter Moon, the inference is that one is looking at the “place in space” where all of us on Earth have just been!)

Making observations and consulting Internet resources provided evidence for which constellations of stars are visible during which seasons. Such evidence provides support for the inference that the Earth revolves around the Sun each year rather than that the Sun revolves around the Earth each day. Making observations and consulting Internet resources also provided evidence for where along the horizon the Sun appears to rise and set, how the length and direction of a gnomon’s shadow changes during a sunny day, and how high above the horizon the Sun transits as it seems to move across the sky. Such evidence supported the inference that the Earth rotates on a tilted axis as the Earth revolves around the Sun.

An important aspect of this model is that the tilt is always in the same direction throughout the Earth’s journey around the Sun. The northern and southern hemispheres experience the effects of this tilt, however, in opposite ways. When one hemisphere is tilted toward the Sun, the other hemisphere is tilted away from the Sun.

This complex model explains that hot summers occur during the Earth’s revolution around the Sun when a hemisphere’s tilt is toward the Sun so that the Sun is high in the sky at local noon, shines more directly down through the atmosphere, and is visible above the horizon for more hours than not visible below. Cold winters occur during the Earth’s revolution around the Sun when a hemisphere’s tilt is away from the Sun so that the Sun is low in the sky at local noon, shines at more of an angle through the atmosphere, and is visible above the horizon for fewer hours than not visible below.

During spring and fall, neither hemisphere is tilted toward or away from the Sun: one hemisphere is tilted toward the direction of the Earth’s motion around the Sun; the other hemisphere is tilted away from the Earth’s direction of motion around the Sun. Acting out these aspects of the Earth’s revolution around the Sun, by leaning always in the same direction while revolving around a lamp in a dark room, can be both challenging and fun for students, whether children or adults.

The unit closes by making connections to educational policies as articulated in the US Next Generation Science Standards (NGSS, Lead States, 2013). As a last homework or question on the final, students use their initial and later responses to the diagnostic questions as evidence for reflecting upon what and how they learned about the Sun/Earth/Moon system during this course.

C. Making connections to NGSS understandings about the nature of science

The Next Generation Science Standards (NGSS Lead States, 2013) recommends that students engage in three dimensions of learning science by using science and engineering practices and cross cutting concepts while learning disciplinary core ideas. In this unit, for example, developing explanatory models for day and night, the phases of the Moon, and the Earth’s seasons are examples of the NGSS science and engineering practice of constructing explanations. Constructing such evidence-based accounts of natural phenomena also exemplifies the crosscutting concept of identifying patterns while learning disciplinary core ideas about the Earth and the solar system.

Children in grades K-2, for example, should learn that patterns of movement of the sun, moon, and stars as seen from Earth can be observed, described, and predicted. During this unit, students predicted rising, transiting, and setting times for each phase of the Moon by interpreting their observations of the shape of the lit portion of the Moon and the angle formed by their arms when pointing at the Sun and Moon if both were visible,

This unit also has provided many examples of the nature of science as articulated in Appendix H of the Next Generation Science Standards (NGSS, Lead States, 2013) https://www.nextgenscience.org/resources/ngss-appendices . Appendix H includes tables that provide insights about the development of these understandings about the nature of science across grade spans of K-2, 3-5 (elementary), 6-8 (middle school), and 9-12 (high school).

That scientific knowledge is based on empirical evidence, for example, is emphasized throughout this course. Unit 5 models NGSS recommendations that children in grades K-2 learn that scientists look for patterns and order when making observations about the world, that upper elementary students in grades 3-5 learn that science findings are based on recognizing patterns, that middle school students in grades 6-8 learn that science knowledge is based upon logical and conceptual connections between evidence and explanations, and that students in grades 9-12 in high school learn that science arguments are strengthened by multiple lines of evidence supporting a single explanation.

That scientific knowledge assumes an order and consistency in natural systems is key to understanding, for example, the cause of the phases of the Moon. By observing the Moon during the first four weeks of the course, the students documented how the shape of the lit portion of the Moon seemed to change. Next, if the Moon were visible during class, they could go outside, each hold a ball up next to the Moon in the sky, and see that the portion of their balls lit by the Sun matched the lit portion of the Moon in the sky (or if inside a dark room with a single lamp, they could each hold up a ball so that its lit portion would match the shape of the lit portion of the Moon they expected to see in the sky that day if the Moon were visible). Then by moving their balls around their heads, they also could make the changing shape of the lit portion of their balls match the same changing shape of the Moon they had been observing in the sky. Finally, they used the understanding that the basic laws of nature are the same everywhere in the universe (grades 3-5) to infer that the changing phases of the Moon they had seen in the sky were caused by the Moon revolving around the Earth just as the changing phases of their balls were caused by moving their balls around their heads.

This unit illustrated that scientific knowledge is open to revision in light of new evidence in several ways. When considering two explanatory models for day and night, for example, an obvious model is that the Sun revolves daily around the Earth. This is what students can infer when they compare the Sun’s changes in position in the sky over several hours. This geocentric model also is embedded in our language with descriptions of sunrise and sunset as well as in tools such as analogue clocks, whose hands sweep clockwise in a circle, like the Sun’s apparent daily rising, moving high across the sky, and setting when viewed from the northern hemisphere.

Some students initially answer the question, “why does it get dark at night?” with a version of the “the sun goes down”. The alternative model is much harder to envision, of an Earth rotating daily on its axis so that the side of the Earth facing away from the Sun is in the Earth’s own shadow. Seeing the model of a spinning globe in a dark room lit by a single lamp helps; in this course, an argument based on evidence occurs in resolving a paradox. After observing the Moon for several weeks, students start to notice that the Moon seems to move daily from east to west during several hours, like the Sun, but also from west to east during several days. They can explain this paradox by understanding that the Earth’s daily rotation on its axis causes the apparent east to west daily motion of the Moon whereas the apparent west to east motion of the Moon over several days occurs because the Moon actually is moving that way as it revolves around the Earth.

Such complex reasoning, based on logic and evidence, is an example of the way scientists gain confidence in one model versus another in their explorations of the natural world. One goal of this course has been to foster such understandings of the nature of science in a context that is familiar and accessible to all.

Question 5.59 What have you learned about science learning and teaching from your explorations in this unit?