Call it Schrödinger's space probe: Voyager I may or may not have left our Solar System. Some of the information the probe has collected suggests that it's slipped the surly bonds of the Sun, while other incoming data leaves scientists believing it hasn't yet crossed that boundary. Both Xeni and I have written about this in the last couple years. At Nature, Alexandra Witze explains why we probably won't know exactly when Voyager leaves the Solar System. Instead, we'll only figure it out when the probe is well past the System limits sign.