Quote:When the DR decides to change history, does that alter the timeline or create another alternate one?
You can't change your timeline.
If the Doctor (Or anyone else for that matter) does make a change to an established history, then all they're doing is creating an alternate timeline. A parallel timeline.
Which is not really that big of a deal, considering that alternate timelines are probably being created naturally every second of every day.
So there would be essentially nigh infinite time lines that the Dr could travel down upon?
That every version of the Dr could be living in one of those lines?
Thought Dr can history his history, but cannot change "fixed points" in time?