I was rereading The Amber Spyglass today, and there's that part when they're still in the Mulefa world and the angel comes to them and is telling them how all the windows will have to be closed. And then
"The way you have [of travelling between worlds]," Lyra said, "is it possible for us to learn?"
"Yes. You could learn to do it, as Will's father did. It uses the faculty of what you call imagination. But that does not mean making things up. It is a form of seeing."
"Not real travelling then," said Lyra. "Just pretend..."
"No," said Xaphania, " nothing like pretend. Pretending is easy. This way is hard, but much truer."
So...does that mean that Will and Lyra could see each other again? Xaphania goes on to say that it takes a long time to learn, though. What is more, it's never mentioned again - their parting is quite final. Although...oh god wait
Xaphania had told Serafina Pekkala that when all the openings were closed, then the worlds would all be restored to their proper relations with one another, and Lyra's Oxford and Will's would lie over each other again, like transparent images on two pieces of film being moved closer and closer until they merged; although they would never truly touch.
So imagine if, on Midsummer's Day, at midday they were both sitting on the bench and their worlds were so close to touching and they were thinking of each other so vividly and then they became aware of someone sitting next to them and they almost didn't want to look in case it broke that fragile interlocking of the universes and yet Lyra knew it was Will and Will knew it was Lyra and then just for a second the two universes were so close and they knew each other so well and they looked up just in time to smile and see that each other were ok before the connection was lost.
