| From the novel, The Great Gatsby, by F.Scott Fitzgerald. This is a symbol of unrequited love and dreams unfulfilled.
"He had come a long way to this blue lawn and his dream must have seemed so close that he could hardly fail to grasp it. He did not know that it was already behind him, somewhere back in that vast obscurity beyond the city, where the dark fields of the republic rolled on under the night." -from the novel (above).
This light, and all it represented, would haunt Gatsby.
As a young child, my mother (an English teacher) had me read this book. Years later, when we moved out to the country we lived on a small lake with lane markers that lit up every evening. 300 feet away from our shore, directly across from us, was marker number 31, with a small green light. It meant nothing to me until I was 20, and had the "first big heartache."
After that I have never forgotten what a terrific symbol that Fitzgerald chose. A light, close but far away, a constant reminder.
On, off, On, off ....till dawn. | 
