Spanish (and indeed most Romance languages) use the article far more than English does, and its incorrect or over use is often a sign of a beginning English learner. In English, the article is ONLY used when making something specific.
So, you could say "the physics of moving bodies," or "the physics of quantum mechanics," but if speaking in general - as here - you would say "physics" without the article. "Physics is a science."
This is simply not true. While it can be a general term, science can indeed be pluralized in English.
One can say that “anthropolgy is one of the social sciences.” My father for many years taught at university in “the college of earth and mineral sciences.” We speak often of “the arts and sciences.”
Here are some of the many examples one can find of this: