"The future ain't what it used to be."

Chronological protection


What if time is linear but time travel is possible?

What I mean is, that in travelling to the past you are only fulfilling your own destiny and not really alterring past events at all?

There used to be this BBC television series called Crime Traveller, in which the main protanganists (Jeff - a police detective, and Holly - a physicist) would use a time machine to solve crimes in the past. The capability of the machine was limited to something like a single day's time travel. Whatever they did, they could not change history, only become part of it. For example, once when Holly went back to tell Jeff that he would be shot later that day, her actions put in motion a chain of events which ultimately resulted in him being shot!

They also could not bring anything back from the past. They always had to return to the machine at the same time as when they left, or else they would be doomed to repeat the day again and again for eternity without realising it. Once they returned, anything they tried to bring back from the past would be erased. Jeff frequently tried to thwart time by trying to win the lottery or something, but in the end, 'time' would always win.

The show puts forward an interesting idea that time can be changed as long as you don't do anything to prevent yourself from travelling back in the first place. For example(not the best example I know, but just take as an isolated incident) in Back to the Future, Doc Brown knows that he will be shot and that Marty will be sent back in time before any of this actually happens. He also knows that Marty can only give him this information in 1955, so when the events unfold, he makes sure that he does nothing that would create a paradox. He could have just not shown up on that particular night to avoid the Lybian terrorists or he might have chosen a different source for the plutonium - but no, he chooses a set of actions which will not interfere with the time line. He wears a bullet-proof vest, and plays dead until Marty can travel back in time.

So what if time travel were to be possible as long as events leading up your departure occur as normal. This reasoning could allow the salvation of people from catastrophes. If you don't know who actually died, it would leave a 'gap' in time, which makes it possible to save these people by returning to the past and taking them back with you to your own time! Yours decision to go back in time has not been altered. As far as your past self knows, these people that you would save are already dead. The only problem lies in the fact that the saved people MUST lose the time between the accident and the time-travel.

What was the point of all this?
First, your thread title was "Chronological Protection".
Then, you talk about an old show on BBC
Then, you talk about Back to the Future.
Throughout, backwards babble which makes no sense whatsoever.
Try to find a point-and then stick to it.

And time is not linear.
The idea was that Time has an inbuilt protection against alterations to history.
All that has happened will happen.
The BBC show was a example of this principle. If someone goes back in time - they were meant to. Or at least time travel is only possible if you don't cause a paradox.
The BTTF example explained this in a scenario probably better well known to people here. eg. that Marty was not prevented from returning back to the past.
And finally I presented my own example on how to travel in time. eg. that as long as you change nothing in the past that would prevent your relevant future self from experiencing the same 'life-line' as you. I say relevant from the point of view of yourself time travelling in the past.

I'm sorry if you didn't follow. Maybe I wasn't clear enough - but please... no need for the attack.