Galileo is under close scrutiny because of his Copernican views. Unfazed, he carries on his research and his teachings. Will the Inquisition bring his demise or will his powerful friends, Pope Urban VIII among them, protect him?

Galileo faces an uncertain future. Behind the scenes are political and religious intrigues and enemies plotting his downfall. The Pope, until now sympathetic to Galileo, has a change of heart. Under pressure from all sides and insulted by his latest works, The Dialogue Concerning the Two Chief World Systems, portraying the Church's view through the character Simplicio (Simpleton), the pope finally sends Galileo to the Inquisition Tribunal.

Galileo is in prison. He tries one more time to prove his theories to his inquisitor. But he finally recants during the trial saying the famous sentence: "and yet... it turns"

In the series "Once Upon a Time... the Discoverers," the Maestro lets off some steam. Some two thousand years ago, Heron invented the steam machine in Alexandria, but it took two millenia to perfect the invention and put it to practical use.

In part two of this series, "Once upon a Time... the Discoverers," Maestro talks about Cugnot, the inventor of the steam traction engine.

Years of research and trial and error culminated in the invention of the first locomotive on rails. Not bad for a father-and-son experiment. That's what Murdoch and his son George achieved in 1797.

George Stephenson tries out his invention, a steam locomotive. He allows his son, Robert, to ride on it as long as he stays on the edge of the carriage and gets ready to jump off if the rails buckle under the weight of the locomotive... which they do. Luckily his son followed his instructions!

The future of the railroad depends on whether George Stephenson's locomotive, 38 cars long, will run or not. The local townspeople debate whether it will go full speed ahead or not budge at all due to its size.

This next part of the Il était une fois series on George Stephenson deals with the Rainhill Trials, a competition that determined what kind of trains (steam engines or locomotives) would be used on the Liverpool and Manchester Railway.

This last part of the Il était une fois episode on George Stephenson deals with the Rainhill Trials, a competition that determined what kind of trains (steam engines or locomotives) would be used on the Liverpool and Manchester Railway. Stephenson proves to be the best competitor.

It's back to the past, with the Once Upon a Time series. How did America get its name? Take a trip back to Renaissance Italy in this first episode of The Explorers to find out.