Behaim had no clue that North and South America even existed. There were three continents Europe, Africa and Asia, and only the great world ocean in between. Like everyone else, he believed that the jigsaw puzzle of geography was complete.

This first globe of the Earth was cutting-edge when Martin Behaim made it in 1492. This is our planet as it was known then, just before Columbus set sail. ' The architecture of our language, myths and dreams comes from that prescientific age. After all, it looks like the Sun and stars all revolve around us. It was natural to assume that we were at the center. How seriously would you take their claim? Our ancestors believed the universe was made for them. Suppose, on one of them, there lives an intelligent species, one the ten million life-forms on that planet, and there's a subgroup of that species who believe they have it all figured out- their world is the center of the universe, a universe made for them, and that they know everything they need to know about it- their knowledge is complete. It's orbited by dozens of planets and moons. How about that star? Or that one? Okay, this one. ' Pick a star- any one of the hundreds of billions of stars in our Milky Way Galaxy, which is just one galaxy out of the hundred billion in the known universe. It's not the kind of experiment that requires a laboratory. I think we're ready to perform an experiment.

What will happen the next time the mob comes? DEGRASSE TYSON: We've come a long way together, traveling from deep inside the heart of an atom clear out to the cosmic horizon, and from the beginning of time to the distant future. So in the fourth century AD, when the mob came to destroy the library and the genius of classical civilization, there were not enough people to defend it.

This was not true in Alexandria, where knowledge belonged to the elite. The collective knowledge of our species, our own electronic Library of Alexandria, may be accessed by anyone who has a device and the interest and the freedom to do so. And all of it all of this is but a tiny fraction of the information that you have at your fingertips at this very moment. They range from 500,000 to nearly a million. Estimates vary on the total number of scrolls. The original manuscripts of the masterpieces of Greek comedy and drama, poetry, science, engineering, medicine and history- the total work product of the awakening of ancient civilization- were kept here.

The Old Testament Bible comes down to us mainly from the Greek translations made here. Euclid set forth the precepts of geometry in a textbook that remained in use for 2,300 years. Here, Eratosthenes, one of the chief librarians, accurately calculated the size of the Earth and invented geography. Every ship entering Alexandria's harbor was searched- not for contraband, but for books that might be copied and stored here, in what was then the greatest library on Earth. Rarely, if ever, before or since, has there been a government that was willing to spend so much of its gross national product on the acquisition of knowledge. The Ptolemys, the Greek kings who inherited the Egyptian portion of Alexander's empire, built this library and its associated research institution. 1 (sail rustling) NEIL DEGRASSE TYSON: The dream of becoming a citizen of the cosmos was born here, more than two millennia ago, in the city of Alexandria, named after and conceived by its dead conqueror, Alexander the Great.

Cosmos a spacetime odyssey