What if he hands an object over or throws it from one home to another, with the public street in between? Here, Rabbi Akiva makes him liable, while the other Sages do not. What is the argument about? Rabbi Akiva says that there is another principle: an object flying in the street is as if resting there. Thus, we view it as if having landed in the street. The Sages disagree with this principle.
But why is handing over forbidden at all? All kinds of labor needed for constructing the Temple are forbidden on Shabbat. And why - because the Temple is the microcosm of Creation. Since the Levites were handling beams from one wagon to another in building the Temple in the desert, this labor is forbidden.
Art: Girl Carrying a Basket by Winslow Homer