tense? I am

I'm writing an SF story set in the near future, but written in the past tense (if that makes sense). The problem is, although not written in the first person, the 'author' must be in the future to write in the past tense, but some of the things written about would/will still be the same when the 'author' is writing, so should they be referred to in the present tense?

The grammars I have say that tense should be consistent, and if I were writing a third person piece set in the past I would use the past tense throughout, however it seems to me that switching tense could make the premise of the story more believable for the reader; then again, it might just bug them.

Not only is this a quandary, it also explains why I post finished pieces infrequently :)