Education and
Public Engagement
at the Lunar and Planetary Institute
Explore! Marvel Moon

Dance of the Moon and Oceans

Adapted from "Tides,"Scientific Explorations with Paul Doherty © 2003, rev. 18 November 2003, the Exploratorium.


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


For the group:

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:


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 that pattern.

Add that the Sun's gravitational pull also helps create tides. However, the Moon's gravitational pull gives the tides their height and regular, daily pattern. An area's geographic location and the shape of the sea floor also affect the tide.

Facilitator's Note: There is a tricky distinction between waves and tides. The waves we like to watch breaking along the beach are caused by wind and are independent of tides. Tides cause the water level to be really high up on the beach, or really far out (often leaving clams and other sea life exposed), and everything in between.

A tidal wave, or tsunami, is caused by a sudden disturbance — such as an earthquake — and is unrelated to tides. If the conversation turns to tidal waves, gently clarify this distinction.

2. Explain that six children will model how the Moon’s gravitational pull creates tides
. Because the Moon and Earth are in motion together as they orbit the Sun, this model will be similar to a dance. Have one child put on the T-shirt and represent the solid Earth. Have four other children wear blue T-shirts and stand in a circle around the "Earth": one behind, two on each side, and one directly in front of "Earth." These children represent Earth's oceans. The oceans are linked by four scarves or strips of fabric that they are holding in their hands. Have all five children stand to face the sixth child, who wears the grey T-shirt and represents the Moon.

We use models to help us represent objects and systems so that we can study and understand them more easily. Scientists use computers to create models to study the complex interactions between the Sun, Earth, and Moon.

Ask the children to recall the scale model that they constructed in Earth's Bright Neighbor: The Moon was held 15 inches (38.4 cm) from a blueberry-sized "Earth."

Explain that while a pair of dancers has to actually touch each other in order to move together, moons and planets can influence each other’s spins and tilts from a distance. All objects that have mass have their own gravity, but only large objects — like planets — have enough gravity to influence each other from afar.

Facilitator's Note: Does the Moon's gravity pull on humans, too? The Moon's gravity affects humans, as well. The tug of the Moon's gravity decreases a person's weight by a few grams. These tides are inconsequential, however, compared to the much stronger pull of the Earth beneath our feet. 

2. Ask the children to demonstrate how the Moon’s gravitational pull creates two tides in most coastal locations on Earth each day.

Have the "ocean" child nearest the "Moon" take three large steps toward him or her. "Earth" and the two "oceans" standing beside Earth take two large steps toward the "Moon." The "ocean" child furthest from the "Moon" takes one large step toward the Moon.

Explain that the water from the oceans has "piled up" under the Moon and directly opposite the Moon. The two children standing beside "Earth" represent parts of the ocean where there is less water.

Note which body parts — the arms or front and back — are experiencing “high tide” and which are experiencing “low tide.”

Facilitator's Note: The formation of the second ocean bulge is simplified in this model and ignores subtle motions of the Earth. A more accurate and complete description is presented in the following sources. Note that the science content level of these sources is intended for an adult audience.

"Our Restless Tides," National Oceanographic and Atmospheric Administration (NOAA)

Bad Astronomy: Misconceptions and Misuses Revealed, from Astrology to the Moon Landing "Hoax"
Philip Plait, John Wiley & Sons, Inc., 2002, ISBN 0471409766

Explain that the model demonstrates how the Moon produces two high tides and two low tides at the same time. The ocean furthest from the Moon is far enough away that it "feels less" of the Moon's gravitational pull.

Invite "solid Earth" to spin about once on his or her axis (the line straight up from the floor to his or her head) a few times to demonstrate about one day. Explain that the Moon is also moving — orbiting around the Earth over about 27 days — and that the oceans are dragged along with the solid Earth as it spins. Have Earth stop spinning in a new position. Note again which body parts — the arms or front and back  — are experiencing "high tide" and which are experiencing "low tide."

Summarize that the Moon's gravitational pull creates two high and low tides for most coastal areas on Earth each day. As the Earth spins, the tide flows in and out.

Part B: What If There Was No Moon?
3. Ask the children to consider what Earth’s tides would be like if there was no Moon. Have the "oceans" stand in their original positions around the "Earth" so that the scarves or strips of fabric are linked in a circle. Have a new volunteer put on the yellow T-shirt and join the model as the "Sun." Invite "Moon" to rejoin the audience.

Explain that the Sun does pull on Earth and its oceans (and keeps them in orbit). Have the children to recall from the scale model that they constructed in Earth's Bright Neighbor that the "Sun" was a pumpkin 491 feet or 150 meters (about three blocks) from a grape- or blueberry-sized "Earth." Since it is so far away, the Sun's pull gives the tides only a third of their height.

4. Have the children model how tides would be smaller on a Moon-less Earth with only the Sun to pull on the oceans. Have the child nearest the "Sun" take one large step toward him or her. “Earth” and the two standing beside him or her take one normal step toward the "Sun." The child furthest from the "Sun" takes one small step forward.

Facilitator's Note: The time of high tide changes each day because the Moon is moving around the Earth. If we had no Moon, the tide due to the Sun alone would occur at essentially the same time every day.


Regroup the children and discuss Earth’s tides — and how different it would be without the Moon's gravitational pull adding significantly to the height of the tides. Explain some of the effects of tides on marine life: Tides create tide pools along rocky shores and where many creatures breed, feed, and hunt. Other creatures thrive in places like harbors, bays, and mangroves where the tide exposes mud flats or tree roots. Tides create currents that mix the ocean, spreading nutrients and removing waste.

Allow the children time to illustrate the influence of smaller tides in their Without the Moon... 3 comic panels.

Studying the motions and gravitational pull of the Moon today helps scientists understand its influence on Earth today — and long ago. Scientists use computer models to help them understand the relationship between the Sun, Earth and Moon — just like the children used their own bodies! They want to know more about how the Moon's gravity has affected the Earth over their long history together. They use mathematics to describe how the masses, speeds, and directions of the Sun, Earth, and Moon interact in space; and the computer combines all of the factors together to show the overall effect. Mathematics and computers are tools for looking at the past, into the future, and considering what might have been!

Now that the children have modeled the Moon's gravity and its major influence on our oceans, invite them to explore further. Invite them to check out books and videos about the oceans, seashore animals, and tides and share them — and their new knowledge of the Moon's importance — with their families.

Invite everyone to return for the next program, Moon Mythbusters, where they will put their science skills to the test!