Sample Lesson - Explore

Purpose

The purpose of the EXPLORE phase is to allow students to explore and “test” their prior conceptions about the relative size of the Earth we live on and the Sun and Moon as the two largest objects in our day and night skies. This EXPLORE phase also serves as a review, application, and extension of previously learned metric measurement and mathematics skills to develop scale models of the Earth and Moon.

Materials

• Create a “Black Bag of Solar System Science” by filling a black trash bag with a ping pong ball, golf ball, and handball [alternative models for the Moon];  racquetball, tennis ball, and baseball [potential models for the Earth]; and volleyball, soccer ball, and  basketball [the largest balls to provisionally represent the Sun].

• YouTube music videos:
  • An online video version of The Galaxy Song with astronomical images and subtitled lyrics can be found at: http://www.youtube.com/watch?v=jsgExTttJ2Y&feature=related.
  • Vangelis’s Albedo 0.39 song that is set against images of the Earth—Moon space program at: http://www.youtube.com/watch?v=rL1oU6fH25w).

• Meter sticks

Activity

1. If not previously discussed, briefly introduce the idea of a model as a scientific tool that allows us to visualize, manipulate, and test something that because of its size, speed, safety risks or other properties cannot be directly examined and studied. Models can be conceptual (e.g., theories), mathematical (e.g., equations, graphs, etc.,), computer-based (e.g., animations and simulations, or three-dimensional, to-scale physical models. Refer back to the images, posters, Earth globe models, and videos displayed in the previous activity and ask:

• Since astronomical objects like the Earth, Moon and Sun are too big to bring into the classroom, what everyday objects might we use as models or “stand-ins” for the real things?

2. Introduce the “Black Bag of Solar System Science” with a bit of mystery by asking the students to guess what you have inside to represent the Earth, Sun and Moon. (For fun, play the “space music” cited in the Materials section as an auditory background). Open up the black garbage bag and begin tossing an assortment of sports balls to randomly selected students. Note: these nine balls are in three size categories to allow students to have the option of suggesting that the three astronomical objects are either all approximately the same size or clearly different in size. (At this point in the 5E you do not need to mention that the largest balls are not nearly large enough to accurately represent the biggest object, the Sun, at the same scale with any of the smaller balls as scale models for the Earth and Moon.)

3. Ask students with the sports balls to hold them up for everyone to see. Have all students complete a Think—Write (their individual guesses or vote), followed by a Pair—Share (to discuss and change their choices if desired) as to which three balls they think best represent the correct rank ordering of sizes of the Earth, Sun, and Moon. During the Pair—Share, ask students to discuss: (1) the source of their estimates about relative sizes; and (2) whether looking up at the day and night skies provides much help. Tally the class results on the board to see how many students correctly identified the relative size order sequence of big (Moon) – bigger (Earth) – biggest (Sun).

4. Introduce information from an “authoritative source” that indicates that the Earth’s diameter is approximately four times that of the Moon. Assign student teams to calculate and/or directly measure the diameter of the different balls to determine which two would serve as the best, to-scale models of these two astronomical bodies. To directly measure the diameter of the balls, students will need a meter stick (or 12” long metric ruler) to place underneath two books that are used as vertical frames to hold the ball in place on top of the metric ruler or stick. Alternatively, students can use a string (or metric tape measure) and metric stick to measure the circumference and then calculate the diameter using the equation: Circumference = p x diameter = 3.14d or Diameter = C/3.14. Note: pi is not typically introduced in 5^th grade math, but it can be empirically “discovered” to a precision of 3.0-3.1 by simple metric measurements (C/d = ~3). See Table 1 (below) for the measured (and calculated) values for the various sports balls.

• This activity can be used to demonstrate that “mathematics and measurements matter when making models.” (Note: The task of uncovering the methods scientists used to determine the actual diameters of astronomical objects (see Table 2 below) must wait until later grades.) Table 2 shows that two different combinations of balls come close to the desired scaled ratio.

Table 1:  Sports Balls Dimensions

Table 2: Earth-Moon Dimensions and Sports Balls Scale Equivalents