> My observation is that most sci-fi is set in a world mostly similar to ours, except for one aspect/tech that's dialed to 11. Fantasy has a much looser attachment to our world, and sometimes the weirder, the better.

I don't remember where I read it but what you just described is one of the best strategies for writing scifi that many of the most well known authors used. I'd wager it is the defining quality of science fiction from a historical perspective: it's a form of fiction that split the difference between vanilla fiction and fantasy that just happened to grow popular in the 20th century's golden era of scientific research. This was the era of boundless optimism with flying cars and the World Fair's Futurama so a fuzzy genre that took our world and changed one abstract thing or dialed it up to 11 (alien invasion! total surveillance! AI! galaxy far far away!) became science fiction because authors chose convenient plot points based on the cultural zeitgeist of the time.

On the surface the difference between science fiction and fantasy isn't all that big ("Any sufficiently advanced technology is indistinguishable from magic") but I think fundamentally they're different approaches to imagining a literary universe. The former is based in reality but the "science fiction" part is a plot device to implement the one aspect of the universe the author wants to change, whereas in fantasy it's supposed to be a new universe whose rules/laws are only vaguely related to our own because the author just happens to also be human.

Edit five minutes later: Found it! Philip K Dick wrote in a letter (from The Collected Short Stories Volume 1):

> I will define science fiction, first, by saying what sf is not. It cannot be defined as "a story (or novel or play) set in the future," since there exists such a thing as space adventure, which is set in the future but is not sf: it is just that: adventures, fights and wars in the future in space involving super-advanced technology. Why, then, is it not science fiction? It would seem to be, and Doris Lessing (e.g.) supposes that it is. However, space adventure lacks the distinct new idea that is the essential ingredient. Also, there can be science fiction set in the present: the alternate world story or novel. So if we separate sf from the future and also from ultra-advanced technology, what then do we have that can be called sf?

> This world must differ from the given in at least one way, and this one way must be sufficient to give rise to events that could not occur in our society -- or in any known society present or past. There must be a coherent idea involved in this dislocation; that is, the dislocation must be a conceptual one, not merely a trivial or bizarre one -- this is the essence of science fiction, the conceptual dislocation within the society so that as a result a new society is generated in the author's mind,

> Fantasy involves that which general opinion regards as impossible; science fiction involves that which general opinion regards as possible under the right circumstances.

> Thus "good science fiction" is a value term, not an objective thing, and yet, I think, there really is such a thing, objectively, as good science fiction.