When man's ambition expanded to fill the solar system, his technology expanded to take him as far as he wanted to go. Technology went on expanding. So did man's ambitions. But there was a danger only dimly suspected, and only poorly comprehended when it began to make itself felt. It was that man's ambition would outleap his imagination; that his technology would outstrip his emotional capacity. It might be that it was just too big, the universe. That there was just too much of nothing there for man to bear.
Used availability for Barry N Malzberg's Universe Day
April 1971 : USA Paperback
September 2011 : USA, Canada Kindle edition
September 2011 : Australia, UK Kindle edition