While the story and the scenery are fantastic in their whimsical scope, the actual technology of Ember will make anyone with even a high school physics education scratch their heads from time to time.
Outside of the minor head-scratchers (no foundry/ironworks? how did the phones and phone lines 'deteriorate'? Why does everything look so weathered in an underground bunker?), one major flaw sticks out at me (!MAJOR SPOILER HERE STOP!) as the three are escaping, they exit VIA this kind of log ride DOWN several tall chutes... yet somehow they emerge several hundred meters above the city and are able to look directly down on it. Who would build such a terrifying escape mechanism to begin with, and how do they gain all that altitude? Overall the movie is nice, but if you have a passion for the sciences you will cringe throughout this movie almost as much as you did while watching The Core (maybe a little less).