30. Earth science#
Role-plays work well in simulating the motion of Earth, Moon, Sun, and stars. You can do them as demonstrations with some students performing the play in front of the class and then as a teacher you get this great feeling that everything must be perfectly clear. However, your students will need additional practice by role playing some tasks in small groups. Do you need this in the age of computer simulations? Yes, the back-and-forth thinking between different representations (role play, computer simulation, figures in the textbook) helps concept development and each representation has its strong and weak point and appeals to different students.
30.1. Visualizing revolution and rotation of the Earth#
The teacher becomes the Sun; a student is the Earth. The student “revolves” around the lecturer while rotating once per 24 hours. Do not let the student rotate 365 times ….
30.2. Visualizing Rotation of the Sun#
While the Earth revolves around the Sun (one revolution per year), the Sun (teacher) is rotating a little also … 12x per year or so. We know this from the “movement” of Sunspots. As a gas sphere, the Sun’s rotation at the equator is slower than near the poles.
30.3. Visualizing Movement of Moon#
While one student revolves around the teacher another revolves around the first student (the Earth), about 13 times per Earth revolution.
30.4. Visualizing rotation of the Moon#
The student (Moon) revolving around the Earth makes sure to keep his/her face towards the Earth……so the Moon rotates one time in one revolution and thus always has its same face towards the Earth. Now compare with the sentences in the book about Moon rotation, do we now understand what the book sentences mean?
30.5. Visualizing parallax for distance measurement#
Same arrangement as in revolution of the Earth. Take a student in the front row as (movie) star and another one in the back. Compare the position of the front row star as seen from the Earth in two positions 6 months apart (figure 1). There is quite a difference in direction of this star. Now look at the student star in the back. The difference in direction from the two Earth vantage points is already a lot smaller. What if the student was very far? This makes parallax as distance measurement visible! Use the meter stick and your arm to show the differences in angles/directions. If you have a string or a rope, so much clearer for your students.
30.6. Apparent movement of the stars throughout the year#
The same arrangement can be used to show the apparent motion of the stars throughout the year. While the Earth revolves, the view of the class (the stars) changes a bit.
30.7. Comet#
The Sun is a lamp on the table or take a student to play the sun. A comet (played by another student) comes from some random direction towards the Sun. What will happen with the velocity and the direction as the comet approaches the Sun? Let the other students give directions to the student who plays the comet about accelerating/decelerating and changing direction. Let them also explain why.
30.8. Visualizing plate tectonics, collisions between thin ocean plates#
The plates are thin, one easily gets below the other. Use two thin books and make them collide slowly back-to- back, one easily slips below the other. The friction of real tectonic plates generates heat resulting in a volcanic island arc.
30.9. Visualizing plate tectonics, collision between a thin ocean plate and a thick continental plate#
Take a thin and a thick book and let their backs collide slowly. Ocean plates have a higher density, so imagine the thin book having a higher density. The thin book slips below the thick one. The friction of real plates generate lots of heat. This way we get the volcanism of the Andes in South America and the Cascades in North America and the volcanoes along the spines of Sumatra and Java in Indonesia.
30.10. Visualizing plate tectonics with islands, accretion#
Now take the thin book (ocean plate) with something on top of it (a cube of sugar, whatever), the denser thin book goes below the thicker and less dense book (continental plate), but the cube of sugar (like an island) accretes to the coast of the continental plate. Such accreted former islands and the continent may have very different rock types.
30.11. Visualizing plate tectonics, collision between two thick continental plates#
Take two thick books, let them press against each other but now take the open sides. The pages will start folding, just like the Alps and the Himalayan Mountain ranges which were both formed by continents pushing each other.