Hey there, this is part two of a two-part episode.

If you haven't listened to part one, I recommend you do.

Thanks.

In 1609, the Italian scholar Galileo took a piece of military spy technology and turned it aloft

toward the heavens.

Human beings had been gazing at the skies for millennia by then, and they of course knew that the moon had

light and dark spotches on its face, the man in the moon and all that.

But when Galileo looked through his military spyglass, now called a telescope, he saw something different.

Wow.

Something new in human history.

You see, during the 1600s, the ancient Greek philosopher Aristotle was highly influential. People called him

the philosopher as if he were the only one that mattered. Among other things

Aristotle argued that heavenly bodies like the moon were perfectly spherical

with surfaces as smooth as polished mirrors.

So everyone in the 1600s believed that as well.

After all, Aristotle, the philosopher, had said so.

Looking through his telescope, however,

Galileo suddenly saw craters on the moon and valleys and mountains.

The moon wasn't a smooth pearl at all.

It was dynamic and rugged.

Now obviously the telescope played a key role in this discovery.

It allowed Galileo to see details hidden from the naked eye.

...