I am in the very early stages of brainstorming for a story, and I have come up with a concept that interests me quite a bit. The only problem is that there is a hole that I can't find a proper explanation to fill. The idea is thus, a lone astronaut wakes up upon his small ship after being under the sleep of cyogenics for an innumerable number of years, centuries, or millennia even and finds himself in a universe he does not know (humanity is gone perhaps? Somehow transported to another dimension?). Coming to this discovery, he goes about progressing through the story (where ever that may take him). My main issue is, why was he put to sleep for so long? I haven't been able to find a reasonable explanation for such a question that satisfies me, an answer that makes a semblance of logical sense.