The Midrash @Barry quoted here, tells us that the special light G-d created was used by Adam HaRishon to see from one end of the world to the other. Later, G-d hid that light and saved it for the Tzadikim in the future.
The Ba'al Shem Tov taught that the light was hidden inside the Torah, and Tzadikim of every generation can use that light to see from one end of the world to the other.
The Degel Machaneh Efraim, grandson of the Ba'al Shem Tov, attests that he personally saw the Ba'al Shem Tov do this many times. He brings one story where the Ba'al Shem Tov sent a letter to his brother-in-law in Israel, mentioning that he (the Ba'al Shem Tov) had seen that his brother-in-law had spent a Shabbos outside the land of Israel. The brother-in-law responded that he went to do a bris milah on Shabbos, outside the land of Israel. How was the Ba'al Shem Tov able to do this? By using the light hidden in the Torah. He further points out that this is hinted to in the Ba'al Haturim, who points out that את האור has the same numerical value as the word בתורה (An English translation can be found here).
Here is another essay that further examines the Ba'al Shem Tov's explanation.
The Gemara (Nedarim 8b) says that the light of the sun was concealed in a sheath, that will be removed when Moshiach comes. Once removed, the true light of the sun will burn up the wicked and heal the righteous. (In English)