Here is a diagram from the Wikipedia. I'm sure you understand what this represents. Those who don't, can go to the Wikipedia page (https://en.wikipedia.org/wiki/Twin_paradox) and see all the details. After my prior post, I have a better appreciation for simultaneity. Originally, when I looked at this diagram, I looked at it using the common meaning of "simultaneous". I thought it was telling me that where the red and blue lines cross the space time lines of the stationary and traveling twins, the twins exist in the same moment from both twin's perspectives. My insight is that the correspondence is just for the traveling twin. The stationary twin will draw different lines. The word (on the chart itself!) "simultaneity" really tripped me up. I'll be honest; even when the diagrams included the stationary twin's idea of simultaneous, I didn't really understand what I was looking at. There's seeing and there is understanding. I'm sure this is so ingrained with experienced physicists that they may not understand why throwing these diagrams at beginners doesn't make things crystal clear. I mean, you even tell the poor beginner what the lines means and he still doesn't get it. Diagrams like this that omit the other twin's simultaneity lines tend to support the wrong idea. Yes, there is a question here. Two, actually. The diagram above assumes the traveling twin can change directions instantaneously. I want to check my understanding. The stationary twin can look at a giant clock attached to the traveling twin. He records the clock and then corrects the recording for light delay. I believe he sees the traveling twin's clock running slow by the same factor on each leg of the trip. The stationary twin also has a clock that the traveling twin can record. The traveling twin corrects his recording for light delay. He also sees his stationary twin's clock running slower and by the same amount on each leg. However, at turn-around, he sees his twin's clock jump forward in time. Do I have it right or am I still missing something? The re-alignment of the spacetime axes of the traveling twin resolves the twin paradox. But I realize I still have a hole in my understanding. If any frame can be considered the stationary frame, is there some perspective in which the traveling twin could assume he was motionless for the whole trip and that the "stationary" twin went out and back? (By the way, I have seen a video that showed just that: the traveling twin stationary while the Earth moves back and forth and claiming that, since everything is relative, either viewpoint is equivalent.) Could we redraw the Minkowski diagram from the traveling twin's point of view? My own attempt at an answer is that, if you change your frame, you can't treat it as though you are motionless and everyone else changed frames. Even if you had an inertialess drive and could switch directions instantly, you could still tell that you changed direction and not the rest of the universe. And if you wanted to draw a Minkowsky diagram for the traveling twin, you would need two, one for each direction. I can say those words, but I have to admit to not having an intuitive understanding of why it's true. My best guess is that maybe inertialess drives are impossible because it would create this very confusion. Someone who didn't see the inertialess drive activated wouldn't be able to tell if they just experienced a change in direction or the rest of the universe did, and the twin paradox would turn into a real paradox. You can't resolve it if everything is symmetrical. Everyone has to be able to agree that the traveling twin was the one who changed direction. Corrections and clarifications welcome.