I was thinking of Time Travel the other day. When we think of our Timeline, we view it as a continuous series of unchanged events and each event leads to subsequent events.
There is a commonly accepted premise that if a Time Traveler were to be inserted into our Timeline at some point in our past, then they might do something to change the events that have led to our current point on the Timeline. The general conclusion is, changing an event would lead to a different future. While I agree with that conclusion, my question is how would we ever know that our Timeline had changed and how would it change. Would our former history be wiped out, or would the Timeline split into two branches. I think it would branch and the way I see it is, making the decision to send or not send a Time Traveler into our past would cause the Time Line to split and the split would occur at the point where the Time Traveler is inserted.
On the branch of the Timeline where the decision was to not send a Time Traveler back in time, no one was sent into the past. Looking back along that branch of the Timeline from a point after the decision is made, what one would see are the events that were always seen before the decision was made. No Time Traveler being inserted and the past events unchanged.
On the branch of the Timeline where the decision was to send a Time Traveler back in time, someone was sent back. Looking back along that branch of the Timeline from a point after the decision is made, one would see the events that were always seen before the decision was made. A Time Traveler being inserted and the past events unchanged.
The only way someone on either branch of the Timeline would know that events had changed would be if they were aware of the events that occurred on both branches of the Timeline. The conclusion would likely be that inserting a Time Traveler does not change the past.
I wonder if this could be built into a story. Perhaps a Timeline Control substation where people from different branches of the original Timeline meet each other. Is there a temporal limit on how far into the past a Time Traveler can be sent? Is there a restriction on Timeline insertions to minimize the number of Timelines? What sort of conversation might the John Smiths from Timelines 1 through 5 have with each other? The bad guys might be Time Travelers trying to split Timelines to create social conditions where they are in power and can do what they want.