Five years ago, I started pondering this question and people have clicked on this essay nearly a thousand times, making it the single most-viewed thing I’ve ever posted. I’d like to continue thinking out loud on the issue now that I’m older and the world has changed a bit...
When I talk about Christianity disappearing in space, I'm talking about the observations that I've made in the reading I've done. I'm a member of Science Fiction and Fantasy Writers of America and am currently on the Norton Award Committee. As part of that group, we read and recommend new SF and F written specifically for middle school/high school/early college aged young people. So far, out of over a hundred novels I've read or previewed, only one character has been a professing Christian. The others curse, talk to gods, goddesses and other minor deities and engage in any number of normal, mundane things -- but they don't appear to be Christians.
Don't get me wrong, it's not amazing to me that author's biases, beliefs, and orientations -- their personalities -- come out in their writing. Someone once made a comment that eventually became an aphorism, "Want to be a writer? Just open up a vein and bleed." An author's philosophy of life becomes clear when we read their writing.
C.S. Lewis, my favorite writer, observed, "We can make people (often) attend to the Christian point of view for half an hour or so; but the moment they have gone away from our lecture or laid down our article, they are plunged back into a world where the opposite position is taken for granted. As long as that situation exists, widespread success is simply impossible. We must attack the enemy's line of communication. What we want is not more little books about Christianity, but more little books by Christians on other subjects with their Christianity latent." (GOD IN THE DOCK)
What I am talking about is that evangelical Christians (or for that matter, evangelical Buddhists, Hindus or Confucianists) have either a) made little or no effort to write stories and novels with latent faith -- or b) Christianity is being supressed by evangelical atheists in the SF/F world. (c) is a hard one for me to consider, but here it is: that Christians, Muslims and Taoists all write bad SF/F. It's possible but on the face of it, unlikely. After all, despite Philip Pullman's rants, people still read Tolkein and Lewis more often than they read him and both of them are Christians.)
Christianity will NOT disappear from space. Christians will "boldly go where no one has gone before" -- as will Muslims, Hindus, Buddhists and atheists. Christian writers need to write GOOD science fiction with Christianity latent in every story. Atheist/agnostic editors and publishers need to quit panicking in fear that publishing stories with Christians in them will somehow undermine their atheist or agnostic beliefs and quit pretending that Christianity (and other faiths) will somehow disappear when the real exploration of the Universe begins. They need to be bold in their willingness to look at futures that might include faiths other than insipid atheism or militant agnosticism...