Relationships are physics. Time transforms things- it has to, because the change from me to we means clearing away the fortifications you'r put up around your old personality. Living with Susannah made me feel as if I started riding Einstein's famous theoretical bus. Here's my understanding of that difficult idea, nutshelled: if you're riding a magic Greyhound, equipped for light-speed travel, you'll actually live though less time than will any pedestrians whom the bus passes by. So, for a neighbor on the street with a stopwatch, the superfast bus will take two hours to travel from Point A to Point B. But where you're on that Greyhound, and looking at the wipe of the world out those rhomboidial coach windows, the same trip will take just under twenty-four minutes. Your neighbor, stopwatch under thumb, will have aged eighty-six percent more than you have. It's hard to fathom. But I think it's exactly what adult relationships do to us: on the outside, years pass, lives change. But inside, it's just a day that repeats. You and your partner age at the same clip; it seems not time has gone by. Only when you look up from your relationship- when you step off the bus, feel the ground under your shoes- do you sense the sly, soft absurdity of romance physics.