10 Major Plot Holes You Probably Missed

7. Back To The Future 3

The Plot-Hole: The Steam-Powered Time Machine

Even ignoring Doc's clearly contradictory, but heart-warming assertion that nobody's future has been written yet, and it is what you make it, the finale of Back To The Future III has a number of glaring questions. Chief among them is how the Dickens the Doc managed to make a time machine that completely runs on steam - presumably including the flux capacitor that previously needed to run on radioactive material - and how he managed to keep it a secret.

The second part seems fairly simple - he hid it - but according to the lore of the first film, the time machine requires either plutonium, or at the very least a modified food processor to run: neither of which Doc had access to in 1885. There is of course a modified flux capacitor at his disposal, which was attached to the time machine that transported him back to 1885 - but the time machine was broken by the lightning strike to the extent that he had to bury it for Marty to rediscover in 1955 so that the 50s version of the Doc could repair it and send Marty back to the future.

So what, Doc took the time machine apart before burying it and made another working time machine with the parts? Then what did he bury for Marty to get back to the future, or the past as actually became his destination? Pick it apart enough and you really get into the complexities of the time continuum.

That's exactly what writers who get confused by their own complex time travelling stories would say anyway. All very confusing, and something that seems to have been ignored largely because of the simple entertainment of Doc's final appearance with his kids in tow.