Origins of '39

From an interview with Brian in "The Guitar Greats" by John Tobler and Stuart Grundy (thanks to Nessa Lopez for typing this in). [Comments] are mine

" '39 is a Science Fiction story I made up, it's a story about someone who goes away and leaves his family, and because of the time dilation effect, where the people on earth have aged a lot more than he has when he returns, he's aged a year and they've aged 100 years, so instead of coming back to his wife, he comes back to his daughter [presumably great grand daughter actually], in whom he can see his wife.

I think I also had in mind a story by Hermann Hesse, which is called "The Poet" [in the interview Brian says "The River", but he is remembering incorrectly - "The Poet" is found in the short story collection "Strange News From Another Star" by Herman Hesse], I think, where a man leaves his home town and travels a lot, then comes back and observes it from the other side of a river and sees it in a completely different light because of his experiences. I felt a little like that about my home at the time, having been away and seen this vastly different world of rock music which was totally different from the way I was brought up. People may not generally admit it but I think that when most people write songs there is more than one level to them - they'll be about one thing on the surface, but underneath they're probably trying, maybe even unconsciously, to say something about their own life, their own experience - and in nearly all my stuff, there is a personal feeling."