1632/Fridge

Fridge Logic

 * The only military threat Grantville could fear was a cavalry raid, (as the slow-movig tercios had no chance against modern guns). So why don't they build at least a wooden palisade around the town? Or at least around the power plant and other important buildings? And why don't they make at least rudimentary flamethrowers? In a world dominated by close combat, they would be much more useful than even the best modern hunting rifles and shotguns.
 * "Rudimentary flamethrowers" is easy? Are you kidding? Even actual military grade flamethrowers could be dangerous to users and could still malfunction. A rudimentary flamethrower assembled by people with no experience building them would be even more dangerous and prone to malfunction. And the 17th century is hardly dominated by close combat, unless you consider marching in ranks and shooting muskets "close combat." There's only a limited amount of modern weaponry, so later in the series most warfare still uses ranks of troops firing single-shot rifles. A short-ranged flamethrower is useless in that style of warfare.
 * If the "Ring of Fire" the town is in is at a depressed altitude from the land around it, why doesn't it just turn into a lake?
 * It's not at a depressed altitude. There are differences in terrain that make some portions jut up and above, some portions are below, and some are more or less on level.
 * But the cliffs are frequently described as forming a ring entirely around the town six hundred feet high -- there should still be a substantial area below the lowest point where it can drain.
 * The average elevation is about the same as before, but the topography doesn't match up, so there are cliffs where a hill on one side of the ring faces a valley on the other. Several of those valleys are drowned. Fortunately for the town, the lowest spot on the ring, where the main creek drains out, faces even lower ground outside. You can see maps of the result here.

Fridge Horror

 * Remember the beginning of the novel, where the Abrabanels get rescued by the Americans? This obviously doesn't happen in the original ("our") timeline. There, the Imperial soldiers caught them... (Likewise, the biography of most other downtimers who found a safe haven in Grantville would probably be a far more gruesome -- and short -- read in the original timeline.)
 * Presumably, an equal-size chunk of 17th-century Thuringia wound up in Turn of the Millennium West Virginia. Presumably there were some, if not many, people on it. What happened to them?
 * Time Spike strongly implies that the US government has them in custody and is trying to hush the whole thing up so they can blame the incident on terrorists. It also strongly implies that the coverup is going to be blown out of the water in short order after the Illinois incident.
 * The prologue to the original book specifically mentions seven dead bodies found by US government investigators where Grantville should have been. The prologue is by an omniscient narrator who explains about the aliens whose carelessness caused the incident. If any transposed Germans had been found alive, presumably the narrator would've known. So either he, she, or it is unreliable, or there were only those dead seven.
 * In-universe: Eddie Cantrell, now married to a daughter of the King of Denmark, mentions in the opening of one book that in the original timeline, she died, apparently of illness, in August 1633 -- ten days after her fifteenth birthday. But the Ring of Fire somehow prevented that, even before Eddie came to Denmark. The revelation still chills the blood of the person Eddie tells it to in 1635; presumably, it bothers him a bit as well.
 * Similarly, whenever a down-timer sees the date and/or circumstances of his/her death recorded in history. Even knowing there are ways they might be able to avert it, especially if it wasn't due simply to old age, it comes as a horrific shock ... and not just to them, but to those they tell about it. French marshal Turenne casually asks Hugh O'Donnell, Earl of Tyrconnell, what the future has in store for the Irishman, and is appalled and apologetic when told, "I am a dead man in seven years."