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Free sample, lesson 1.2, animation
A rocket goes up because it throws hot gas down. It is the same rule that sends you rolling backward when you throw a ball from a skateboard.
Thrust is a push. But what does a rocket push against? Under it there is only air, and in space there is not even that.
Play through the five scenes. In every one, something gets thrown one way and something else moves the opposite way. Spot both each time.
More than 300 years ago, Isaac Newton wrote down a rule that has never been broken: when you push on something, it pushes back on you just as hard, in the opposite direction. Scientists call it Newton's third law of motion. We will call it push back.
You felt it in the first scene. You pushed the ball forward, and the ball pushed you backward. A heavier ball, or a faster throw, means a bigger push back.
A rocket engine is a machine for throwing. It burns fuel to make very hot gas, then throws that gas out of a bell-shaped nozzle. In the big engines of the Artemis rocket, the gas leaves at about 13 times the speed of sound. The engine pushes the gas down. The gas pushes the engine, and the whole rocket, up. That push back is the thrust you met in lesson 1.1.
So a rocket does not push against the ground, and it does not push against the air. It pushes against its own exhaust. That is why rockets keep working in empty space. They even work a little better there, because no air is in the way.
Wow factIn 1920, a famous newspaper made fun of the rocket scientist Robert Goddard. It said a rocket could never work in space, because there would be nothing to push against. In 1969, while astronauts were on their way to the Moon, the newspaper printed a correction.
Sit on a rolling desk chair on a smooth floor and lift your feet. Throw a basketball or a heavy pillow straight ahead, as hard as you can. Your chair rolls backward. You are the rocket, and the ball is your exhaust.
Check first that nothing breakable is in front of you.
Think about it: an astronaut is floating next to the space station, holding a wrench, when her safety line comes loose. She cannot reach anything. How could the wrench get her back?
23 lessons over five weeks: real films, games you play, builds at home, and a final project reviewed by an instructor. Then a certificate with an ID anyone can check.
More free samples: 1.1 What a rocket has to beat, 2.2 Why rockets curve sideways
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