I'm in Paris, about which I'll have much more to write later. But along the way I've read two science fiction books, both older, both brought along from our used book sale.
The first I believe I read years ago: "Time-Scape," by Gregory Benford (1980). But it holds up, a complex book that predates Orson Scott Card's "Pastwatch" by many years: in the future (1998) the world is on the edge of ecological collapse. A desperate experiment ensues to communicate via tachyon beams with the past, the 1970s. The book is fascinating on many levels. It talks about the intersection between politics and science -- meaning the pursuit of funding. It illuminates the politics within academic institutions despite what is nominally supposed to be the pursuit of truth. And finally, the book is about the open-endedness of the universe. If the message is successfully communicated, the present ceases to be. And by the end of the book, at least three endings are presented: all "real."
The second book was "Guardian" by Joe Haldeman (2002). It's a fast read, about a woman who marries a twisted but not very realized character, has a son by him, then, when the son is 14, flees the husband when he sexually abuses the son. It's a period piece: Dodge City in the late 1800s, a brief look at the Alaskan gold rush -- and abruptly, an encounter with the Tlingit myth of the Raven. The woman, with Raven, experiences multidimensional travel, and then is returned to a moment before a tragedy. This time, it plays out differently.
So I picked up two books at random, written over twenty years apart, to discover that both are about alternative timelines, about redoing the past with the knowledge of the future. Or as Heinlein once wrote, a paradox can be paradoctored.
My family had a great conversation last night about the feeling of deja vu. I experienced that often as a young teen, although rarely since then. Both of my children report experiencing it, too, as well as dreams of buildings they've never seen -- only to come across them months later.
Current physics suggests that the flow of time is not necessarily in one direction only, and that perhaps our decisions branch into whole new universes, all existing at the same time. So maybe those moments of deja vu and "precognitive" dreams are nothing more than moments when our perceptions jump track.
Or maybe it's just a trick of the temporal lobe, tuning itself through adolescence. There are many universes in our brains, too.