Most kids have heard the old saying, “What goes up, must come down.” This movie will explore the force of gravity. It will teach the difference between mass and weight, explaining how weight is the measure of how much gravity pulls on an object, while mass is the amount of matter in something. In the movie, Annie and Moby will compare gravity’s pull on a few different bodies in our Solar System, including the Moon, Jupiter, and Pluto. Help children explore the world around them and understand the force that keeps the entire universe together!
Throw a ball up in the air. What happens? Have children explain that the ball falls down to the ground. Explain that the ball falls because of gravity. Gravity is a force that pulls objects together. Earth’s gravity pulls everything downward. Without it, everything on our planet would float away.
Review with children that mass is the amount of matter in an object. Since all things have matter, all things have mass. But, some things have greater masses than others. Brainstorm different items with various masses and compare them. Which has more mass, an elephant or a mouse? A book or a pencil? A bowling ball or a basket? Guide children to understand that things with larger masses are not necessarily larger in physical size. For example, a balloon might be bigger than a baseball in diameter, but a baseball has a greater mass. Explain that objects with greater mass have a stronger force of gravity.
Throw a ball up in the air again. Explain to children that the ball has mass, but Earth’s mass is much, much greater. When you throw a ball, Earth’s gravity pulls the ball down. Without gravity, the ball would continue flying up and up.
Many children have seen images of astronauts walking on the Moon. The Moon has less mass than Earth, so the force of gravity there is much weaker. That is why astronauts can jump high on the Moon. They can jump far and high, but they will not float off the surface because the Moon’s gravity still pulls them back down. On Earth, we cannot jump as high because our planet’s force of gravity is much stronger.
Remind children that mass and weight are not the same measure. Weight is a measure of how much gravity pulls on an object. Mass is the amount of matter an object has. On the Moon, gravity’s pull isn’t as strong as it is on Earth. So a child who weighs about sixty-five pounds on Earth would only weigh about ten pounds on the Moon, about the weight of a small dog. Help children understand that weight changes with gravity, but mass always stays the same. The amount of matter in an object doesn’t change depending on where the object is in the universe.
Explore weight on other bodies in our Solar System. Jupiter is the largest planet and has the greatest mass. Thus, its force of gravity is much stronger than Earth’s. A child who weighs sixty-five pounds on Earth would weigh about one hundred fifty pounds on Jupiter, about the same weight of a washing machine. The mass of Pluto is much smaller than Earth. A child who weighs sixty-five pounds on Earth would weigh only about five pounds on Pluto. That’s about the same weight as a sack of flour. Help children understand that in space, there is very little gravity. Astronauts in space are practically weightless and so they can float.
Gravity keeps our universe together. On Earth, it keeps us on the ground and prevents us from floating off the surface of our planet! What might life be like if we lived on the Moon? Or on Jupiter? Have children imagine a world where gravity is weaker or stronger than on Earth.