Soon after entering elementary school, he began to express a strong inquisitiveness about nature.
Sagan recalled taking his first trips to the public library alone, at the age of five, when his mother got him a library card.
He wanted to learn what stars were, since none of his friends or their parents could give him a clear answer:

"I went to the librarian and asked for a book about stars ...

And the answer was stunning.

It was that the Sun was a star but really close.

The stars were suns, but so far away they were just little points of light ...

The scale of the universe suddenly opened up to me. It was a kind of religious experience.
There was a magnificence to it, a grandeur, a scale which has never left me. Never ever left me."