Greek cosmology

[Belacqua]

There were Greek philosophers who, several hundred years BC, speculated as to whether the stars were suns like ours, but very far away, with inhabited planets going round them.

It's always amazing to me how much they were able to figure out, without modern methods. And without coffee!

Bishop Nicholas of Cusa, almost 100 years before Galileo, suggested that the universe is infinite, that the earth is not the center, and that aliens out there might be looking back at us. We owe a lot to these creative thinkers. 

Here is a good, careful, propaganda-free blog that traces the history of these issues:

https://thonyc.wordpress.com/