1 Answer

Heluva question! The old-timey (think of the Greeks; the word comes from them) notion is that of discovering the laws of physics. those formulas and such involving mass and velocity and acceleration and time.
Part of the difficulty here is that it is the beginning of science, this particular way of acquiring knowledge. Perhaps you remember a bit of it from school. First a hypothesis, then testing, then evidence, then verification.

Anyway, getting back to physics. It's the physical world. I know that's not terribly helpful, but hold on. Metaphysics is about the physical world. It's not very verifiable, and so it's part of philosophy. When the Greeks, and others, told a story about the causes and effects in this world and posited why this was, they told a myth. In our present understanding, myth means "not true." Whenever you try to answer the questions: where did I come from?; who am I?; where am I going?; you are at the limits of science and thus speaking mythically.

Within physics are theoretical and applied physicists. As example, Einstein discovered Relativity, but it took years for other physicists to test and eventually accept it as fact. Soon thereafter, applied physicists built the bombs we dropped on Japan.
I use that example to emphasize the truth with a small "t" of physics and science. Their facts are not to be challenged, until they are! And then they say, "Well, yes, it seems we had that bit wrong." And so it goes.