I know it's impossible to tell at this point (I also don't know if it's been talked about here before), but the use of Allomancy and "faster-than-light" travel through space is really bugging me (from a physics point of view).
The thing is, given that nothing in our universe as we know it can travel faster than light, there are only a few logical possibilities of what happens: 1) Time as we know it stops; 2) You travel so fast that planets die within a short amount of your time (for instance, the light speed in Star Wars would've made it so Vader was dead by the time they made it to the Death Star); or 3) You teleport instantaneously. I've been trying to figure it all out by myself, but besides being given the fantasy element, there has to be some sort of scientific logic behind it. I can't really see myself believing any of it otherwise.
Or am I just digging too deep at too early of a time?