I always feel like "hypothetical history of science" questions are kind of impossible, but here's a go anyway:
Imagine that, for the entirety of human history, EM radiation from anything beyond the Kuiper belt was totally obscured. No star besides the sun had ever been observed, and in particular no large scale structures like galaxies have ever been directly observed. In such a world, it's possible that we'd still be clueless about dark matter, since the relative orbital periods of stars around our galactic center were the impetus for positing such a thing.
I'm interested in the kinds of physics we'd have available if we couldn't rely on long range astronomical observations. To narrow the focus a little more as one commenter suggests: In particular, how much of relativity would be available from local observations? Would near-earth time dilation effects be enough impetus to develop (if perhaps more slowly) the entirety of general relativity? If not, what are the likely missing pieces?
(The specific narrative motivation here is, if the situation above held, and our intrepid protagonists stumbled across a traversable wormhole, whether they would have even the faintest idea what they were looking at.)