Care to explain? Because what I gathered from the wiki entry about the Novikov-principle is that, if the theory is correct, a "grandfather paradox" is completely impossible to occur (which is depicted CORRECTLY in the movie when Cooper, inside the tesseract, fails to make himself stay at home in the past) because this particular part of history has happened that way and thus cannot be changed.
Applied to the grandfather example, it would mean that it even if you could travel to the past it would just be completely impossible for you to kill your on grandfather before you are born; or that it would impossible to go to the past to kill Hitler, because that would mean the motivation behind the time travel would never have existed in the first place.
So far, so good, so Novikov. In this movie, however, there's also an ontological bootstrap paradox, i.e. where an information/entity/whatever has no more discernable origin.
I also read Kip Thorne's wiki entry (the guy who did the actual physics for Interstellar) and from what I gather there, he mostly says that timetravel might actually be possible. It says nothing about this particular kind of paradox but maybe I'm just too dumb.
So the past can't be changed anymore because Cooper HAS to get into the black hole and relay the necessary information so he could end up there in the first place, fair enough. However, without the wormhole, the tesseract etc. humanity would've gone extinct so they could've never developed into "5d beings", so those beings could've never sent a wormhole back in the first place to save humanity or build the tesseract or anything. The technology/advanced state of being/wormhole that saved humanity has no real origin anymore. It's more of a metaphysical than a physical paradox, the way I see it. And it pisses me off. It seems so lazy.
I also read Kip Thorne's wiki entry (the guy who did the actual physics for Interstellar) and from what I gather there, he mostly says that timetravel might actually be possible. So I guess the physics are right (or at least possible), but the horrible bootstrap is Nolan's very own fault.
I'm not a physicist, but this is how I see it and I'm horrified by the fact that a promising movie ended so stupidly. The love-stuff, holy cow...
12 Monkeys is still the only movie that did timetraveling really well in my eyes.
Sorry if this sounds like gibberish, but english is my second language and this shit is confusing enough to write about even in my first.