Note I post these PP every other day.
When I was a very young lad-I couldn't have been more than seven at the time-I found a map of Greater New York. I had never seen a map before and I hadn't the faintest notion what it was.
There were curious shapes, and there were lines crossing here and there, and small print everywhere. However, as I studied it with puzzlement and curiosity, I came across some fairly large print which said BROOKLYN.
That excited me. After all, I knew that we lived in Brooklyn. The common conversation I heard from grown-ups around me made it clear that Brooklyn was home. I therefore looked eagerly for other words that made sense, and eventually I discovered the names of streets that were familiar to me.
I remember the feeling of awe and gladness that I experienced. After all, my horizon was very close to my center, and I hadn't the faintest idea what lay beyond it. I therefore strongly suspected that the map I had which listed the streets I knew and many, many that I didn't know in dim faraway places like Queens and Manhattan must be a guide to the whole world-even the whole Universe.
I soon learned better, for in school, I eventually received geography books with maps covering more ground and I found that Brooklyn and even all the five boroughs of Greater New York are but an insignificant patch on an inconceivably larger world.
I felt the loss. For a brief period of time I'd thought I had a clear representation of everything there is, and that my knowledge was (at least potentially) total. To be introduced to misty distances plunged me into a rather fearful unknown.
From this introduction, Asimov segues into a discussion of how mankind learned about its existence in the universe - not as the center of the "musical spheres", with the sun circling us, but as us just an insignificant speck whirling around in a galaxy, which was whirling around other solar systems in other galaxies.