Headscratchers / Safety Not Guaranteed

• So when did he do it "once before"?
  • A test run of some sort. Possibly a scale model that didn't require stealing as many materials. Alternately, it could have been a full-scale short run but the technology could break down after one trip.
  • Or could have landed somewhere where he couldn't retrieve the time machine. One thing many time travel plots forget is that the Earth isn't a static location, it's constantly moving in its orbit and one needs to compensate for that. Consequently, the machine could have appeared in or above a large body of water, in the middle of a highway, anywhere.
    • I've seen many people cite this as an issue with time travel, but since it's never expressly stated that they do not take the entirely predictable movement of the earth in its orbit into account, I don't know why it keeps being brought up.
    • Entirely predictable, but there are still many variables: Earth's rotation, wobbling on its axis, continental drift, revolution around the sun, sun's movement relative to galaxy, galactic rotation. Experimenting with time travel doesn't mean one has the background in astrophysics to make all those calculations correctly.
    • Predictable on the macro-scale but on the micro-scale, nothing's particularly predictable just very probable. Also, the fact that we do experience the arrow of time suggests that while the math says the laws of physics are reversible, there is some mechanism that makes them not reversible.
    • It's predictable, sure, but that doesn't mean the method of compensating for it is easily doable. The Earth orbits the sun at about 18.5 miles per second, so it wouldn't take much of an error for the result to be catastrophic - just destroying the time machine in a way that doesn't kill the traveler (or, if it's an unmanned test, doesn't make it impossible to verify that it worked) would be a pretty massive success for an experimental system.

• Another time-travel problem; if Darius succeeded in saving her mother, wouldn't she then never have said in the first place, since her mother has been alive the whole time? If subscribing to the maybe-maybe-not logic that Kenneth saved Belinda, then Darius's mother would have been saved, too, and she would have known. Or would this be explained away with the alternate universe theory that Kenneth had been describing?
  • If Kenneth's explanation of the Belinda situation is correct, the universe apparently compensates for the grandfather paradox. It could be that anything needed for the time traveler to make the changes in the past is carried over into the new timeline, even if it's memories that conflict with the new reality. It could even be the case only in situations that matter for the time travel - in Darius's case, it could be that her mother is indeed alive, but from when Kenneth asked her why she wanted to time travel, after which knowing her mother was alive could cause her to not time travel, she remembered only the timeline in which she died. Effectively, everything - actions, memories, et cetera - needed for the time travel to happen in the first place might take place in an alteration-proof bubble in the timeline.
    • Given that she handwaves to her colleagues that her parents are divorced and that's what she was trying to change, it would be possible for a new timeline to have led to that divorce and estrangement which would leave a mostly-consistent universe. But the easier explanation is that Kenneth was just embarrassed to admit the real reason he wanted to travel to the past and a successful time jump would create a new timeline.
  • Or maybe Kenneth really is insane, there is no time travel, and all he’s created is a machine that quietly and tidily disintegrates itself and anyone on it.

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