Note: This post has been automatically imported from my old blog. Formatting may be incorrect.
I'm looking for examples of theoretical knowledge (in any field) that, while true in some context, had no proposed practical applications at the time they were formulated. It's ok if they've since had direct or indirect applications. I want to investigate a hypothesis about why I think the pursuit of knowledge needs no further justification qua productive enterprise once it's shown that the knowledge is connected to reality, no matter how abstract or esoteric the subject.
Some potential examples of what I'm thinking of (might be wrong here, need to research the history of these): Much of number theory (Euclid didn't forsee RSA when proving the infinity of the primes), astronomy before Newton (did Copernicus know his work would lead to a unified theory of force and gravity that enabled countless mechanical technologies, among other things?), Mendel's genetic research (I'm guessing 23&Me was far from his mind), etc. I'm particularly interested in examples from the humanities, as I'm quite lacking in those myself.