User blog comment:Cualabear2/Porphyrion( didn't spell that right)/@comment-67.163.29.102-20111211223715/@comment-3146930-20111212144713

This is going to sound a bit nerdy, but I'm going to use Doctor Who as an example. The Doctor talks about fixed points in time. These are events in time that must happen and cannot be changed no matter what. However, some events are fluid and can be changed or altered. Using an example from the series, Percy being given the knife by Annabeth is a fixed point, but the choice to give Luke the knife or not was a fluid point in time and could have gone either way