I don't know if this story will inspire or depress..
Many years ago when I was a graduate student, I got interested in a certain 'side project'. It was just something that captured my interest, but I knew it wasn't important enough to make a major focus of my work. For about 3-4 years, I occasionally worked on this project with 2-3 other friends from grad school, slowly collecting enough data to start figuring things out. When I became a professor, I advised an undergrad student for a senior thesis on the topic, and we wrote a paper together. That was good, but that paper just scratched the surface, and I felt strongly that there were more things to investigate. But again, it was never a priority.
Over the years, I never quite gave up on the project. I kept thinking about it, acquiring new data, and writing bits and pieces of a manuscript. The work sort of became a joke with some of my grad school era friends. They would ask "How's Project X going?" and I would say that it was still going.. slowly as ever. But not long ago, I finally finished the manuscript with help from a few grad school friends, it got pretty good reviews, and last night (late of course, as is fitting for a manuscript that took insanely long to construct), I resubmitted the revised version.
One of the things I like most about this paper is that all my co-authors are friends from grad school, even though we now work on different research topics. I told one of my former professors from grad school about the paper, and he was very pleased. It made me realize that I would also find it thrilling if some day a group of my former grad students get together and write a paper, independent of anything they ever worked on with me.
10 months ago