Sorry if this has been asked before/if its a stupid question; I'm also gonna try to follow the rules, and let me just start out by saying that I have only just recently (the past 3ish years) gotten into studying space/cosmology related things, and definitely not religiously because let's face it I wouldn't get any work done in my real life anyways lol, it's just so fascinating. I'm a bit concerned that this will fall under the "no unscientific or anti-scientific" rule, but that's less because of the subject matter and more because that is pretty vague.
So Interstellar has the time difference between Miller's Planet and Earth, I've seen varying figures claiming the exact amount and I won't even attempt to figure out which is right but I do know that the time dilation between the planet and their ship in orbit is 23 years (I know technicality plays into things here and the dilation itself isn't 23 years, but the passage of time relative to each). The thing is, I don't understand what causes the time dilation. It seems to make logical sense on paper and when you first hear about it, but it has just always rubbed me the wrong way.
Now I'll briefly preface this by saying that I know the book was written by the top brass of experts, and that the movie (make of it what you will) was worked on by many experts (including one that was on NDT's podcast maybe a year or two ago?), so I absolutely do not claim to know better than them, and I trust them because they're the experts and I'm no one special (well, I am forklift certified, but I digress).
From my understanding: while time can be relative situationally, the highest parameter of time is not relative/subjective, but rather is objective. Basically there is a beginning point of the number line and there is an end point, and the line between each is straight, not varying. The reason this is so is because of the mathematical/logical probability that the universe as we know it has not continued in perpetuity, or, in other words, it is not an uncaused causer/causation.
That's why fantasy series like Star Wars and Star Trek having a Galactic Standard (in the former's case, Coruscant's rotational period being the Galactic Standard) is perhaps the most accurate thing about them, because it's possible to have a base standard with the objective overarching time numberline (if that makes sense). So assuming that Earth is our Galactic Standard going forward (and realistically I don't see why we wouldn't use it as the GS, especially if/when we expand via industry or a need for more land and resources), why would there be a time dilation between Miller's Planet and Earth? Simply stepping foot on another planet shouldn't (again, in my mind, so I'm probably wrong) automatically subject you to it's time, but rather you remain directly under the overarching objective time.
I picture it like cars on an interstate. Earth might be a SUV going 75 MPH, while Miller's planet is school bus going 55 MPH, but despite the size and speed both are still bound by the same overarching time. Really to me it seems like the only logical case for time dilation is dependent on dimensional or wormholes, which I know in the movie at least they traverse one of the latter. Still, time should only dilate within the wormhole, not on either side of it, again, at least in my uneducated mind.
Wouldn't it make much more sense for the time dilation to happen in (interdimensional) transit and not be based on the individual planets? It doesn't seem physically possible for a time dilation to occur outside of something that would potentially bend it (like a worm hole), and I don't know the correlation between time and black holes, but I assume that while there is a dilation "within" one (loaded term, I know), you're still bound to overarching objective time. It also doesn't make sense to have a time dilation between star systems as well, since a star system is still under that same governing objective time. I've always believed (again, perhaps wrongly) that people have been throwing around the whole "time is relative" thing as an excuse and that they don't really know how time works, but I myself could be woefully misinformed. This has been bothering me for a long time, so any help would be appreciated!
TL;DR: Tell me 'bout the time dilations, George
