תלמוד תורה כנגד כולם That is there is a mishna in tractate Peah: that brings a list of the commandments that have no lower limit. E.g., charity. That means even the smallest coin. [It does not mean that one ought to give just the smallest coin. Rather that even with the smallest coin one has done a good deed.]And after that list it brings, "learning Torah is equal to them all." The Gra explains that even with one word of Torah, one has fulfilled the commandment of learning Torah.

The Rambam brings in laws of learning Torah that the things that he explained in the first 4 chapters of the Mishna Torah that are called "Pardes"  (Physics and Metaphysics as he explained in greater detail in the Guide for the Perplexed) are in the category of the Gemara  [That is learning the Oral Law in depth.] So  every word of Physics is included.