Audience: Early elementary students
Objective: Students will act out the movement of the tides in relation to the gravitational pull of the sun and the moon.
Materials: Large red circle or ball to represent the sun; small white circle or ball to represent the moon; globe; group of students.
Background info: Prior to this lesson demonstrate the rotation of the Earth on it's axis, the revolution of the Earth around the sun and moon around the Earth. Give background information on tides including the following information: Earth is the water planet; water movement on coastline is sometimes high on shore (high tide) and sometimes farther out from shore (low tide) - called tides; caused by gravitational forces of the sun and moon; since moon is 200 times closer than the sun, the moon's gravitational force is stronger; most coasts have 2 high and 2 low tides approximately every 24 hours (most areas in Gulf of Mexico have 1 high and 1 low tide per 24 hours; gravitational pull on Earth's water causes tidal bulges; centrifugal force causes bulge from moon's pull on one side of earth to be equal to the bulge on the other side of the earth; neap tides(lower range of tidal movement than average) are caused when the sun and moon are at right angles; spring tides (higher range of tidal movement than average) are caused when sun and moon are in line with earth; spring and neap tides occur 2 times per month.
Procedure: Present students with background information. Students hold hand and stand to form a circle. Teacher chooses one student to act as the stationary sun by holding the big red circle and one student to act as the moon. Place globe in center of group to represent our planet. The other children holding hands will be the water on Earth. Teacher can stand in middle of group with the globe to help direct the students movement. Teacher directs the "moon" to walk slowly around the "water" (outside of circle) of the Earth. Teacher directs students to slowly take one step backwards (bulge) as moon passes near and students on opposite side do the same because of centrifugal force (teacher standing in middle with outstretched arms can be pointing to students who should be bulging out). As moon passes by, step slowly forward to original position. Teacher can direct the moon to stop at several spots to let the class see where high and low tides are in relation to the moon's orbit and to comment on how the pull/bulge feels. Repeat with other students acting as sun and moon.
Assessment: Teacher observation of students bulging and returning appropriately.
Lesson plan by Terry Hartnett.
