Dance of the Moon and Oceans
In part A, children ages 10 to 13 discover how the Moon's gravitational pull causes the level of the ocean to rise and fall twice a day along most coastlines. Six children represent the oceans, solid Earth, Moon, and Sun and move their bodies to show the interactions of these elements. In part B, they consider what the Earth's tides might have been like if there were no Moon. They model the smaller tides that would be produced solely by the Sun. Allow 30 minutes for this activity.
Note that this activity is appropriate for older children (ages 10 to 13) who are able to explore the geometry of Sun-Earth-Moon relationships in three dimensions. Many children under 10 are not able to fully conceptualize the Earth's spherical nature and their relationship to it, and so they are unable to create an accurate mental model.
What's the Point?
- The Moon's motion in orbit around the Earth and its gravitational pull results in an observable phenomenon at Earth's surface: tides.
- Tides are the daily rise and fall of ocean waters along coastlines. They reach a maximum height known as high tide and a minimum height known as low tide.
- Tides have important effects on marine life and ocean currents.
- The Sun also pulls on the Earth and oceans, contributing less than half of the total height of the tides.
- Without the Moon, Earth would have smaller tides generated only by the Sun's gravitational pull.
For the group:
- Images of high and low tide in the Bay of Fundy, preferably printed in color
- Optional: Images of high and low tide at a local ocean beach photographed from the same location, preferably printed in color
- 1 large, brown T-shirt
- 4 large, blue T-shirts
- 1 large, grey T-shirt
- 1 large, yellow T-shirt
- 4 blue scarves or strips of fabric
- Art supplies, such as colored pencils, crayons, and markers
- Books and videos about oceans, seashore animals, and tides for the children to check out after the program
- Books about the Moon and tides; for instance:
Moon and Tides
Rob Lang, Creative Teaching Press Inc., 2009, ISBN 1591987083
After providing basic information about the Moon, the author discusses eclipses, gravity, and tides. Appropriate for children ages 9–12.
Exploring Our Solar System
Sally Ride and Tam O'Shaughnessy, Crown Books for Young Readers, 2003, ISBN 0375812040
This well-illustrated book takes children ages 9–12 on a tour of the planets (and our Sun!) in our solar system. In addition to clear explanations of lunar phases and Earth's seasons and tides, this book includes a timeline of major events in the history of our planet.
For the children:
For the facilitator:
- Review the background information.
- Print images of high and low tide. You may choose to present images of the Bay of Fundy, or you may wish to provide your own photographs of a local coastline or from a beach vacation. Be sure to photograph high and low tide from the same location for easier comparison.
- Display several books and videos about oceans, seashore animals, and the Moon and tides in a place where the children can page through them before and after the activity. Encourage the children to check them out at the end of the program for further investigation.
Facilitator's Note: This activity builds upon the fact that the Moon has gravity, but the children may have false ideas about the concept of gravity. You may wish to first undertake the activity Heavyweight Champion: Jupiter, where children ages 9–13 can discover whether other planets and the Moon have gravity and what causes this natural force.Advanced learners may wish to explore the complex relationship between the Moon (and its phase), the Sun, and Earth. Older children may create their own tide wheels.
Part A: The Moon’s Gravity Creates Ocean Tides
1. Ask the children to consider the reason behind the difference between images of high and low tide. Show the images to the children and have them describe the differences between them. Guide their discussions toward identifying them as tides, and finally, toward relating the Moon as the main cause of t