What is considered a part of "learning Torah" is extremely important because of the sin of "bitul Torah".[Bitul Torah means the very severe sin of not learning Torah when one is able. ]
So when some rishonim [mediaeval authorities]like Ibn Pakuda and the Rambam include Physics and Metaphysics in the category of learning Torah, the significance is great. What I mean is that one is obligated to learn Torah all the time. And if Physics was not a part of Torah, then it would be possibly bitul Torah. [Unless one was doing it for the sake of making a living.]
The significance of the concept of bitul Torah is not just to make one guilty if e is not learning when he could. Rather it is to point out the awesome sweetness of Torah that one would not give up after having tasted it even once. The only thing is thatt I am saying that to some rishonim, math and physics come under the heading of "Learning Torah"
To so degree you can see this in Psalms 77, 105 and other places where it says to speak of God's wisdom in his creations.
