Our English word science derives, ultimately, from the Latin verb scire, which meant “to know.” In modern English, though, science doesn’t refer simply to knowledge in general. Rather, it denotes a certain kind of knowledge — or, even, to be really precise, a certain methodology (or bundle of methodologies; after all, cosmology and botany and geology and particle physics and genetics and astrophysics and ecology employ quite distinct methods and styles of reasoning) for attaining that certain kind of knowledge.
Very few if any people in the English-speaking world, for instance, would describe art history as a “science.”
Is history, more generally, a “science”? Some historians have aspired to that status — Leopold von Ranke’s famous goal of recording or writing history wie es eigentlich gewesen (“as it actually was”) surely expresses some such ambition — but most today probably don’t. And, while history can be ranked among the “social sciences” (as at BYU), it’s often placed within colleges of “Arts and Letters”). And it’s arguably at least as close to literature as it is to nuclear physics.
Is “political science” really a “science”? As practiced by some (e.g., by those who work with survey data), it may tend in a genuinely “scientific” direction. But more than a few “political scientists” are either uncomfortable with or irritated by the notion that they’re doing “science.” Courses on political philosophy, for instance, don’t seem “scientific” at all — though that doesn’t even begin to render without value the study of Plato’s Republic and Laws, Aristotle’s Politics, or the work of John Rawls.
There are valuable areas of scholarship, study, and thought that have nothing to do with “science” as it is generally conceived in English.
In German, though, the word Wissenschaft is quite a different matter. On which, some additional notes to come.
If you’re interested in the topic at all, I think there’s good reason to expect that you’ll find this provocative article extremely interesting:
On the outer edges of current astronomical research:
“Two black holes are thought to have formed a new black hole 80 times larger than the Sun and sent ripples through space-time”