this is something ive thought about. I know that jj abram's trek is set in an alternate timeline, due to the romulans coming back in time. What is the difference between that, and "Yesterday's Enterprise" where the timeline was altered by the enterprise-C? in that episode the prime timeline was messed up by that. so doesnt the same logic apply with the romulans going back in time? messing up the timeline? not creating an alternate timeline? or are they both alternate timelines? im probably thinking about this too hard. lol