The study of diseases and their treatment is arguably the oldest science.
There doesn't seem to be a question about medecine on the site now (perhaps because most participants are from existing Stack Exchange sites and there isn't one about medecine?), but I don't see why it would be off-topic.
It would seem that space exploration is on topic (eg. "Why it did take so many attempts before the Russians managed to land a probe on Venus?" "Who discovered Titan?"), but what about geographic exploration? It seems to me that as with the social sciences, there is a line somewhere. E.g.
Determination that the North Pole was not a large magnetic mountain
Questions on Amundsen's magnetic observatory during his NW Passage voyage
Questions on meteorological, natural and geological observations made by Darwin & Humboldt during their voyages
Who was the first person to visit both Poles?
Questions on the subsistence lessons that Amundsen learnt from the Inuit and other native people, on his NW Passage voyage
How did Mallory & Irvine probably fail in their ascent/descent of Everest?