The TVTropes article also points out that “hardness” in science fiction is always subject to change. Science continues to advance, and often stories that are written on the best science available at the time turn out to be only fantasy. On the other hand, news headlines today could make something written as fantastical, futuristic SF suddenly reality. This was also pointed out by Vivienne Raper in her article. The rate of change in science and technology is one of the things that discourages SF writers from attempting to grapple with even the near future. You could be in the midst of writing a hard SF novel when your science suddenly becomes obsolete. On the other hand, you could be in the midst when suddenly you find you’re writing non-fiction. Cyborg roaches? No problem.

TVTropes points out that, because of these changes, the hardness rating of SF can easily change over time. However, they suggest that the rating should be based on science during the time period in which the work was written. In other words, Jules Verne wrote hard SF, even though we know he was off a little bit in what he predicted.