Katherine watched him forlorn on the big sofa. This was her home, not his. He had been thrown from almost certain damnation into something stranger. Only time would heal the stress and disbelief.
"Always," she shrugged. "When most people travel, most humans anyway, they need to go linear. You can't just go from A to D without also crossing B and C. I can, that's what we did. But some jumps are even to big for me. So, you need to bend things, you need to forge connections where naturally where are none. Same goes for time... time for you only naturally goes one way. Forwards, step-by-step. It doesn't have to. You've seen Thanos do so with the time gem. He stepped back. We are in a different universe, if you want to return to yours, you need to find it and somehow manage to create a bridge and no one knows at which time point that universe will be then. Time isn't always running at the same speed in every universe and sometimes even within a universe." Einstein and stuff. They had had special lessons about the science of different universes back in the 26th century. For people like Katherine, it was important. Different worlds were just as important to island folk as photosynthesis was.
After the long explanation, Katherine decided not to answer his other questions. Let him have time to query her on this matter before any of the others. There was something, however, she could add. She let a bottle and two glasses appear. It was a fine make - crystals that shimmered when hit just right by the light. She poured him a glass before pushing it towards him. "Here, I'm sorry, it's just water."