He folded his arms and sat back against the chair.

Ms. Belfry looked triumphant. Thats quite right, Oliver.

She turned back to the drawing and added arrows. Oliver felt a paper ball hit his head but this time he didnt even react. He didnt care anymore what his classmates thought of him. In fact, they were probably just jealous that he had brains and knew cool stuff like Isaac Newtons laws of physics when all they could manage was screwing up a ball of paper and aiming it at someones head.

He folded his arms more tightly and, ignoring the paper balls smacking him in the head, focused on Ms. Belfrys image. She was drawing an arrow pointing down. Beside it she wrote downward force. The other arrow shed drawn pointed up with the word lift.

What about hot air balloons? a voice challenged from behind. They dont work that way at all, but they still fly.

Oliver turned in his seat, searching for the owner of the voice. It was a grumpy-looking kiddark, bushy eyebrows, dimpled chinwho had joined Paul in throwing the paper balls.

Well, thats a completely different law at play, Oliver explained. That works because hot air rises. The Montgolfier brothers, who invented the hot air balloon, realized that if you trap the air inside some kind of envelope, like a balloon, it becomes buoyant due to the lower density of hot air inside compared to cold air outside.

The boy just looked more angry at Olivers explanation. Well, what about rockets? he challenged further. Theyre not buoyant or whatever you just said. They go up, though. And they fly. How does that work, smarty pants?

Oliver just smiled. That comes back to Isaac Newtons third law of motion again. Only this time the force involved is propulsion, not lift. Propulsion is the same thing that moves a steam train. A big blast out one end produces an opposite reaction of propulsion. Only with a rocket its got to get all the way to space, so the blast has to be really massive.

Oliver could feel himself growing excited as he spoke about these things. Even though all the kids were staring at him like he was a freak, he didnt care.

He turned back in his seat to face the front. There, smiling proudly, stood Ms. Belfry.

And do you know what all these inventors had in common? she said. The Montgolfiers and the Wrights and Robert Goddard, who launched the first liquid-propellant-fueled rocket? Ill tell you what. They did things theyd been told were impossible! Their inventions were crazy. Imagine someone saying that we could use the same principles of ancient Chinese catapults to launch a man into space! And yet they became groundbreaking inventors, whose inventions have changed the world, and the whole trajectory of humankind!

Oliver knew she was speaking to him, telling him that no matter what people did or said, he should never be cowed into silence.