Torah that Flows Like Water - Parshat Nitzavim-Vayelech

This week's parsha says that the Torah is no longer in the heavens. Instead, it is for us on Earth. Rabbi Glenn Black of NCSY Canada points out that this same line appears in the Gemara, where it describes an argument between Rabbi Eliezar and the sages and three surprising miracles unfold to prove his point. Why does a carob tree uproot itself, a stream flow backwards, and the walls of a Beit Midrash bend?