Science fiction postulates possible futures based on technological innovation. Even when the extrapolated future is hundreds, thousands, or millions of years down the line, the premises of science fiction books have an inherent knowability. Science fiction books like Dune and Foundation push the boundaries of what technology can do to humanity, taking scale and physiological transformation to extremes. But even in these stories, there is an inherent knowability to the universe. The exact opposite is true of cosmic horror stories. Here’s more on cosmic horror from the Los Angeles Review of Books:
To appreciate the cosmic mystery that Lovecraft so obsessively tried to convey and conjure to hideous life in his stories, we are invited to consider human knowledge as a flat plane in the middle of black depths of outer space. The plane is thin, fragile, and ever-tilting, like a huge pane of glass. Everything within that plane has been explained and understood: terrestrial biology, classical physics, physiology, large swaths of human history. But as soon as you step near the edges, you face the abysmal immensity of all that is unknown: numberless galaxies, planets, and stars that have existed for billions of years; white dwarfs-cum-black holes dense enough to bend time; an infinite kaleidoscopic expanse, potentially just one of many infinite expanses in a hydra-headed multiverse that perpetually begs the question of its own sentience.