The scientist Kilowog trains Hal Jordan in the rudimentary basics of wielding a Green Lantern ring. He taught Jordan how to fly, make a protective shield around his body, make energy blasts from the ring. They did all this without knowing the very basic fact about the ring: that it’s powered by will power. Perhaps that revelation is reserved for future volumes of the series, or maybe it’s a twist and we learn that the rings aren’t powered by will power at all. Wouldn’t be surprised by that since the Earth 1 series is full of these twists.
From – Green Lantern – Earth 1