I've been reading a lot of physics lately, which is something I haven't really done in earnest since my later high school and college years. At the time, I had reached the saturation point for what my adolescent brain was capable of absorbing in abstraction, and to dig any deeper would require mathematical training beyond my patience or capacity.
My math is most certainly even weaker now than it was then, but fortunately, the nearly two decades that have passed have opened up other ways of thinking about some of these fundamental laws of time and space, matter and energy, chaos and order. Not in anyway relevant to the fields of physics, mathematics or information, but in how I think about the world I experience. But to get there, we will need a quick, non-mathematical, primer on the relevant physics...
The universe is way, way, WAY weirder than most people think. It is also far more interesting, far more elegant and far more beautiful than anything dreamed up in the minds of men and women. But most people are unaware of the true depths of strangeness that the universe reaches, because most people are still at least a hundred years behind the times, living in a clockwork Newtonian universe where everything is neat, orderly and mostly fits in with what we call "common sense." (Actually, many people are closer to five hundred years behind the times, stuck in an Aristotelian conception of the universe in which bowling balls fall faster than tennis balls because they are heavier, which is not the case.)
But the universe we inhabit is much, much stranger than all that. While I could give many examples, only one is relevant here, and the rest would get us off track. Take a photon. Photons are, as most people know, the smallest reducible "bit" of light. (As soon as you start talking quantum or relativistic physics, you have to hedge all of your definitions, since a photon is simultaneously both a wave and a particle. And that's not even the weirdest thing about it.) You are able to see the world because millions and billions of photons are striking your retina every moment your eyes are open.
But the strange thing about photons is that they don't actually "travel" from point A, say a light bulb, to point B, your retina. What modern physics has learned, quantum mechanics in particular, is that we can't ever say that an individual photon took such-and-such a path to get from point A to point B. All we can say is, "Here are all the possible paths the photon could have taken from A to B, and here are the probabilities that it took each of those paths."
Let me repeat this. A photon leaving light bulb A, is nowhere to be found until it strikes your retina B (or some other thing it interacts with along the way). It "leaves" the bulb A, "chooses" one of an infinite number of possible routes, "travels" that route, though without actually travelling the route, and "arrives" at your eye, causing you to be able to see whatever it is you are looking at (it'd have to actually bounce off whatever you're looking at, of course, but that isn't really relevant here, because we aren't concerned with how vision works). All we can do is calculate the likelihood that it took each (infinite) potential path and, taking all of these probabilities together, use this sum to describe the "route" the photon took.
Whew. Now if that sounds like cockamamie horseshit (and it should), slow down for a second, and consider two relevant factors. Number one, all of the truly weird aspects of quantum mechanics, this being one, have been experimentally verified to something along the lines of a factor of one in a billion billion. That means that experiments have verified the theoretical predictions to roughly the 18th decimal place. That's pretty good. That would be like launching a rocket from earth and hitting a dime on the moon. Every time. That doesn't happen by accident.
Number two, think about where your brain comes from. Your brain evolved over the last few million years largely on the African savannah to be pretty good at communicating, problem-solving, tool-crafting, mating, politics, etc. Nowhere in there was it ever critical to our survival to appreciate the deepest workings of nature on unfathomably small (or large) scales. In fact, it is a testament to our great fortune that some of our savannah-useful skills happen to translate into something useful for probing the fundamental depths of the universe. (I mean, we could have been born dolphins. Dolphins are wicked smart. Dolphins have names. Dolphins have good taste in music (oh wait, that's killer whales- whatever). But dolphins will never build a Large Hadron Collider.)
Now, here is where it gets really weird. (No, like, really, really weird.) Physicists have been working for the last century or so to explain what this, the weird travel habits of photons (and every other particle in the universe), actually mean. Only one of the possible explanations is relevant here, but trust me when I say, the explanations are even more counter-intuitive than the phenomena itself.
The one explanation that we will consider, not because it is the most right (in fact, it is probably the most wrong), but because it is foundational to what I actually want to talk about, is the Many Worlds Interpretation. The Many Worlds Interpretation of Quantum Mechanics posits that, essentially, everything that can happen, does happen, albeit in an infinitely branching series of increasingly different universes. In other words, for every possible path the photon could take, it does take, but it only takes one in any particular universe.
Now, for the most part, physicists hate this interpretation, for obvious reasons. It leaves reality a convoluted, messy, insane place. But, it does make the math work, and as has been shown time and time again, when the math talks, it is usually worth listening. Mostly, however, Many Worlds is acknowledged as a possible explanation for the weirdness of the universe we find ourselves in, but since it is, in principle, completely untestable, it is largely swept under the rug while a more satisfactory explanation is sought.
What I want to do today, though, is to imagine for a moment that the universe does work like that, but I want to scale up from the "choices" photons make to the ones that we do. Going through a major life change, as I recently have, has left me spending lots of time wondering, "What if?" Even more so, I have had numerous conversations with other people wondering, often more feverishly, "What if? What if this? What if that? Whatifwhatifwhatif?"
Our lives are full of choices; what friends to keep, what college to go to, what to study, what job to take, what girl to ask out, who to marry, where to live, whether to have children, whether to stay married, whether to change careers, and on and on... Each of these choices, in a very simplistic sense, represents a single branch on the tree above, let's call it The Tree of Potentiality. Each of these choices, once made, precludes us from making a host of other choices that were previously open to us. (In fact, this is just another way of explaining mid-life crisises. Do you remember being 18? That feeling that you could do anything, absolutely anything with your life? Chances are, if you're 28, or 35, or 50, or 80, this feeling has progressively dimmed. At some point along the way, when people realize this, they throw a little tantrum for a bit.)
The thing about the Tree though, is you can only move in one direction along it. You can only travel from the base, or the trunk, to stick with the metaphor, up through the limbs, down the branches, out to the twigs. We all get this, at least intellectually. You can't be 18 again. You can't travel back in time, or undo the past.
But what a lot of people don't seem to get, at least on an emotional level, is that you can't travel parallel, either. You can't hop from one branch to another. But when people ask, obsess, over whatifwhatifwhatif? that's precisely what they are hoping, wishing, to do.
Again, let's play Many World's for a minute. We can use my life. Under these presumptions...
There's a universe (a whole bunch, actually) where I never climbed onto the roof of that elementary school, never got arrested and never solidified my relationship with the kid that turned out to be my longest and best friend. (Those would all be sucky universes.)
There are universes where I took applying to college seriously, and didn't end up at a place where I really didn't belong...
But then I wouldn't have ended up in the universes where I met other great friends, and never would have moved years later to Seattle to visit one of them...
And wouldn't have met a whole host of wonderful people there...
And there are universes where I stick around there for the woman who was, at the time, the love of my life...
But then I wouldn't have moved back to Maine, continued cooking, met the woman who would become my wife, and who would give me my incredible daughter...
And, of course, there are universes where that woman is still my wife, and we are still happily married.
It's those last universes that some people in my life, at least right now, keep wanting to leap to, when they ask whatifwhatifwhatif?
But we can't. The universe doesn't work that way. We "make" our choices (nod to the free-will discussion that we clearly don't have time for here), we travel down the branches of the Tree, and we come, every moment of our lives, with every thought, word and gesture, to yet another intersection that opens up new possibilities while precluding others. And all we can do is make the best choices we can, with the information we have, between the branches in front of us.
We can't go back. We can't even go sideways.
All we can do, and thus all we should ever want to do, is move forward. All the rest is futility.
All we can do, and thus all we should ever want to do, is move forward. All the rest is futility.