"It's impossible to physically travel back in time".
The "misfire" shot an energy burst back.
So if the girls could work out how to target it they could send bolts of energy to different points in history...Hilary struck by lightning before messing with Pip...History being made better by certain people being struck by bolts of energy.[/quote]
Actually, it's quite possible they COULD send physical objects if said objects were converted into energy and then back to mass later a la Star Trek.