The question I have is, doesn't John have to send Kyle back before Skynet sends the T800?
No, because Skynet failed before it ever sent a terminator back. That's the only reason John even exists in the first place.
Agreed, but that's a different issue. My question is, in the examples of the first three movies and the instances of Skynet/Resistance time travel, doesn't John have to launch a preemptive mission to the past in order to have any hope of affecting the outcome? T1 would otherwise have been successful in his mission eventually if not for Kyle Reese. The T-900 likewise if not for T2 and the T-X if not for T3! In each instance there is an attempt to protect Skeynet's target in the past with a time traveler ordered to protect Sarah Connor and/or John Connor. If Skynet is first to send any Terminator, the T-800, T-900 or T-X then it should meet no resistance from the future and eliminate John Connor's influence on subsequent events.
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You are making the mistake of assuming that the time travel even happens in the future, and then changes made to the past propagate into the future. This requires multiple time dimensions and is incorrect. In essence, you have the order of things backwards.
The past effects of the backwards time travel happen before the backwards time travel occurs. It doesn't matter when Kyle steps into the time macchine, or in what order. All that matters is when he appears in the past, and where, and what actions he takes there.
From John Connor's perspective, and the perspective of an outside observer, the events of The Terminator and of Terminator 2 have already happened. They're written in stone before Skynet even builds the machine.
As I explained earlier in the thread the reason why Kyle Reese and John Connor didn't vanish when the T-800 went back was because the temporal energies inside the time sphere protected them. They were in the chamber when the T-800 went back so they weren't affected by the changes to the timeline caused by the T-800 and they were able to send Kyle back in time to stop the 800. Because of this new timeline now there would exist a reality where Connor knew of all the proposed attacks upon him because he would have experienced them. I think arguing about temporal paradox has given me a headache.
But there was a reality where John Connor was born not to Kyle Reese but someone else.
Temporal energies? Seriously? That's very scifi pseudosciency. I prefer my Terminator harder than that.
The propagation of a field change across closed timelike curves always results in the initial conditions. This provides a hard limit to the potential energy states of a universe in which CTCs are possible, and fulfills Novikov's self-consistency conjecture.
Thorne's and Klinkhammer's solution to Polchinski's paradox confirms Novikov's conjecture, suggesting that alterations to the past are impossible. Though it shows that there are in infinite number of self-consistent trajectories along any CTC for any initial conditions, it also demonstrates that each of these trajectories has a distinct quantum probability. Quantum waveform collapse would produce a single set trajectory that would be unchangable.
In modeling the CTC created by Skynet and Jon Connor, one can treat Skynet, the T-800, Sarah Connor, John Connor, and Kyle Reese as a single system. Their interactions create a single self-consistent worldline.
This remains true up to Terminator 3, in which case things change, which I prefer to choock up to an error in T3's than a mistake made by Novikov, Thorne, or Klinkhammer.