It's actually quite obvious: This entire song is one whole big metaphor: "Half a world between us" could be an actual half world (Earth) or metaphorical world but it describes a divide the writer see between him/herself and the subject. "Gravity will bring our orbits together" simply means that no matter what we do, we always find ourselves in the same place. It could be that it's someone he/she always runs into or someone they are always drawn to. Either way, the subject is important in a way that the writer can never seem to separate themselves from. Minus energy, Gravity is relentless and will always win.
It's actually quite obvious: This entire song is one whole big metaphor: "Half a world between us" could be an actual half world (Earth) or metaphorical world but it describes a divide the writer see between him/herself and the subject. "Gravity will bring our orbits together" simply means that no matter what we do, we always find ourselves in the same place. It could be that it's someone he/she always runs into or someone they are always drawn to. Either way, the subject is important in a way that the writer can never seem to separate themselves from. Minus energy, Gravity is relentless and will always win.