He shouldn't have been able to go back to see Emma

the 1890s logic of time travel was a time-machine can travel through time like a ship through water, not only to places where other ships existed. but really the time machine itself has to become removed from the timeline of the universe in order to travel through it in that context, so by it existing at any point in the timeline it's capable of moving through that timeline.

by your logic (which i mean it's all time-travel, so yours is just as sound as mine) the time machine would only be capable of traveling within the machine's actual lifespan (from creation to first issue that impedes its function, where you could stop, fix it, and maybe keep going). but that also puts a limit on where a person could travel, they'd only be able to travel within their own lifespan, which makes for less interesting stories.

the biggest problem with Emma was that since her death inspired the time machine, simply by it existing when he went back to save her, she has to die again. or if she didn't, the time machine and Alex would have to cease to exist the moment she was safe (again less interesting for storytelling). really the thing with time travel is unless you're in a purely observational state, removed from the timeline (let's say, inside the bubble, for this particular machine) there's a good chance that the simple existence of you and your machine in the past would alter the future to the point where the second you put it in park you and the machine would cease to exist.

the idea of splitting timelines is kind of a egotistical human approach to time travel, at it's base level we think we could create a universe simply by existing, whereas it's much easier for the universe to simply blink us out of existence (we're not that important to it). whether or not time travel for humans is possible, it's probably pretty safe to say that altering the past is impossible. i dunno about traveling to the future, perhaps you could only move forward in time, it depends on the relative nature of time and space, if on a universal scale there even is a "present" to use as a benchmark, or if that's a uniquely human way of looking at things.

then again, i'm no physicist so what the hell do i know? just the fun theories of sci-fi movies. for all i know since all matter in the universe was created in the big bang, by traveling through time, you'll create a moment where the same two bits of matter (you, and wherever your matter was at the time you traveled to) exist at the same moment in the universe, and for all we know the whole damn thing might be fragile enough that you could wipe out existence with just that.

The time machine shouldn't have been able to go back in time to when Emma was still alive because the time machine wasn't even built yet.

"Champagne for my real friends, and real pain for my sham friends..."

[deleted]

That's only a theory. In his novel Timescape, Gregory Benford theorizes tachyons allow time travel into the past before the creation of a time machine because time is more akin to a landscape than to a river.

Personally I've never bought the idea that a time machine, if possible to construct, would be limited only to being able to travel to the point of its origin.
Requiescat in pace, Krystle Papile. I'll always miss you.

The only thing time travel is determined by is whether you change the past, not whether something from the future can exist before it was made.
In other words, Causality.

If Alex had changed events so that Emma lived, the version of himself that went back in time to change those events would never have existed.
Certain events must then be unable to be changed.
At this point it would have to create multiple universes to allow for this loophole, or time itself may break. We have no idea what a paradox would actually do.


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"I wasn't paying attention, that makes it a plot-hole!"
-The Average IMDB Thread

There are lots of different theories of time travel, how it works, it's limitations and how paradoxes are resolved. Here paradoxes are apparently resolved by something that stops the action that would create a paradox, in essence a kind of "magic" or super intelligent force would have to intervene (sending the horse leading to emma's death). I find this theory rather implausible but it does fit nicely with the story in a poetic way.

What you are talking about is the theory / rules for primer.

It is only a movie. So, the time machine can do whatever the writer(s) say it can do.

This isn't Primer. The Time Machine doesn't have to be in existence for him to travel back in time. By the rules exposited in The Time Machine,.. he could visit the time of the dinosaurs.