I don't have an answer but 1,000 questions instead. I'm not a math guy but am usually pretty quick to grasp concepts. If someone wouldn't mind helping me out with the conundrum of Gargantua v Miller's planet, I'd be very grateful.
At the heart of my questions is the concept of gravitational time dilation. If I understand correctly, when gravity is X, then time dilation is Y. In other words, the ratio is constant. (I know, this is dramatic oversimplification but bear with me.) So, on Miller's planet, which is being affected by the blackhole's gravitational field, 1 hour = ~7 Earth years given the Earth's point of reference related to Miller's planet. However, on board the Endurance, which is also presumably being affected by Gargantua's gravity but to a slightly lesser degree Than Miller's planet, one would expect the degree of time dilation to be less than what is experienced on Earth. Correct?
For example, Endurance is experiencing gravity at X while the Ranger is experiencing gravity at Y. You can then simply perform X-Y, the result of which is the difference between gravitational forces on the two bodies in question and presumably the gravitational time dilation between them as well.
However, in my example above, X is really measured as X meters per second squared (m/s2), right? Essentially, the measurement is based on the excelleration of the body caught within the gravitational field. Essentually we are measuring the different rates of excelleration between the Ranger's passengers and the Endurance's.
All of that said, I cannot believe the passenger on Endurance waited 22 relative years for the occupants of the Ranger to return 3 hrs after leaving to Miller's planet. I haven't done any math, but aren't we talking about ~1 minute here, at most, if in fact the Endurance was orbiting Miller's planet?
If I am correct above, let's look at Earth in the same context. In Earth's case, the calculations become much more complex. You have to account for the difference between the Earth's speed vs Miller's planet, the chance in speed differentials as the planets revolve around there gravitational governing body. (For example, when the Earth is orbiting away from Miller's planet, the difference between the two bodies' relative speeds increases, right?) Further, the angle at which Earth observes Miller's planet changes the relative perception of Miller's planet's movement. Then you have to account for the speed at which the Galaxy in which Miller's planet exists is racing away from the Earth as well as the many variables associated with this movement.
In short, the time dilation associated with the relativistic movements between Earth and Miller's planet likely needs a super computer to calculate, I think.
Even then, the gravitational time dilation caused by Gargantua is likely a small contributing factor when calculating the actual relative time dilation between Earth and Miller's planet.
And if I'm on the right track, I don't even want to think about what happens when Cooper shows up on Dr B's planet, although I might travel a great distance to start a population with Anne Hathaway.