Reading a bunch of old (or based-on-old) science fiction made me think about a very peculiar characteristic of old sci-fi that gives it a strange sort of freedom:
Ignorance (amazingly!)
Consider--an author writing science fiction a hundred years ago would have different ideas of how the universe or solar system was constructed. For example, the proliferation of science fiction in the early 1900s that portrayed Venus as a hot, watery world, or the "canals" on Mars, or the notion that the life on the planets became older and wiser as you got further from the sun.
Consider also--a concept of interstellar travel unaware of the limits of general relativity or time dilation, positing a spacecraft with zero mass, and determining speed by simply equalizing thrust with drag! (as in the Lensman series)
In this video, I consider these examples and the possibility that, the more we know about the universe, the harder it is to write science fiction that follows that knowledge.