The class record observations of the Sun's apparent motion or path through the daytime sky from East to West. This activity of tracking the Sun's path along the Southern horizon should be repeated 3 times a year during three different seasons.
Panoramic photo labeling in Science Notebook during Activity: Part 1 Intro
Panoramic photo data recorded in Science Notebook with follow up questions:
Computer generated illustrated model of the Sun's path with written explanation using computer graphics software (i.e. KidPix) to illustrate and answer the following questions:
The apparent motion of the Sun across the sky from East to West, as well as the similar motion of all celestial objects, is explained as a result of the motion of the Earth and us with it. In fact, as we shall see later (in Activity 7) the actual path of the Sun's apparent motion reflects a somewhat complex interplay of the Earth's rotation, the resultant change in our orientation depending upon our latitude, and the position of the Earth in its orbit (Activity 9).
Our purpose in this activity is not to discuss any of this. Rather, we wish to create a baseline of concrete observations common to the entire class, to which we will refer as we work through our understanding of the motions of the Earth/Sun/Moon system. This activity is also an excellent opportunity to introduce the importance of careful, systematic observation and of presenting and sharing the results of observation in a clear and accurate way. It also invites students to realize that underlying our ability to comprehend nature is the fact that our observations reveal repeating, predictable patterns. In essence, science is the process of discerning, describing, and explaining these patterns.
There is a somewhat subtle point here, on which educated adults have been known to be unclear. The issue may not come up in class until later activities, but we chose to address it early here. We typically describe the apparent motion of the Sun, as mentioned above, as a result of the Earth's spinning motion about its axis. The idea that the Sun is in fact moving around the Earth, it is thought, was overthrown by the Copernican revolution of the 17th century. This is, in fact, false. Indeed, all of our observations suggest the Earth is spinning about its axis, completing one rotation every 24 hours or so. These observations include the apparent motion not only of the Sun but also of all other celestial objects, essentially anything in the Universe that is not on Earth. One can, without contradiction with observations, say that the Earth is not spinning. But one then has to claim that the entire Universe is in fact spinning about the Earth as a center. One also has to posit some rather unnatural causes for the (weak, but certainly measurable) centrifugal forces that we ascribe to our motion as the Earth rotates. Most unnaturally, one will note that all the other planets in the Solar system, and indeed all other celestial bodies, rotate about their own axis in addition to their apparent motion about Earth. It is thus far more natural to assume Earth is also in constant rotation about its axis. But fundamentally, taking the point of view of an Earth-bound person, describing the Universe as revolving around the Earth, is consistent if not simple.
The revolution engendered by Copernicus was not associated to this question at all. Instead, it addressed the fact that planets appear to be moving relative to the stars, in addition to the apparent uniform motion of everything that is explained by the Earth's rotation. This motion of the planets is far slower than the daily rotation of the entire sky, taking months or years to complete a cycle, depending on the planet in question. Before Copernicus, these apparent motions of the planets relative to the stars were explained by having planets move along complicated trajectories about the Earth (epicycles). Copernicus showed that the same apparent motion resulted from far simpler, essentially circular, motion of the planets around the Sun, provided we allow that we observe this from an Earth which itself orbits the Sun. The complicated apparent motions are the result of viewing simple motion from a moving platform. One can maintain the point of view of a stationary Earth even after Copernicus, at the cost of having the entire Universe perform a yearly compensating motion, but the level of complexity involved in this choice becomes so high that is is rarely attempted by scientists.
Group Size: Whole class and small group recording teams
Each student needs:
Part 1: Science Notebook Intro
Daily Sunrise and Sunset times:
Recording the daily sunrise and sunset times is a wonderful everyday morning meeting activity. Each day a student or you can research the sunrise and sunset times from the local paper or website. Chart the times to notice patterns and an order to the sun's time spent moving across our sky. Additionally, add to the chart the high temperature of the day and see if they discover any patterns. These data can be graphed and interpreted to better understand the sun's path diagram.
Track the sun's movement by tracking a stick's shadow each hour. Much like the sun tracking groups each hour have a group track the stick's size, shape and direction each hour. Check out http://hea-www.harvard.edu/ECT/Stick/stick.html#intro for a great lesson that helps your students record the smooth arced motion of the sun across the southern horizon.
Sun's Path in the Southern Hemisphere:
Present students with the animation at arb.nzcer.org.nz. Challenge them to compare this with their observations. The sun's path in this animation is reversed relative to our observations - the sun appears to move from right to left - because this animation was designed in New Zealand, in the Southern hemisphere. This challenge foreshadows later activities in which we will introduce the effects on our observation of the sun's apparent motion of the fact that Earth is round. It will likely puzzle students and keep them guessing; a promise that this will be explained later will build excitement and curiosity.
K-6 Astronomy activities from Harvard-Smithsonian Center for Astrophysics' Everyday Classroom Tools at
Language arts and Astronomy connections at Stanford's Solar Center at
Earth, Sun, and Stars Teacher's Guide by LHS GEMS
Lawrence Hall of Science University Of California at Berkeley
Horizon: the line where the sky and the Earth appear to meet
East, West, North, South: the four cardinal directions on the compass
Semi-circle: the shape of half a circle
Altitude: elevation above the horizontal, describes a direction
Landmark: An identifiable, readily visible object in a landscape, used as a reference point for describing other locations.