Dreaming the past

My novel In the Midst of Lions opens with a character named Mary Hansard -- an ordinary forty-something high school physics teacher -- suddenly realizing she can see the future.

More than that, really; she now has no reliable way of telling the future from the past.  She "remembers" both of them, and if she has no external context by which to decide, she can't tell if what's in her mind occurred in the past or will occur in the future.  Eventually, she realizes that the division of the passage of time she'd always considered real and inviolable has changed.  Instead of past, present, and future, there are now only two divisions: present and not-present.  Here's how she comes to see things:

In the past two months, it felt like the universe had changed shape.  The linear slow march of time was clean gone, and what was left was a block that was unalterable, the people and events in it frozen in place like butterflies in amber.  Her own position in it had become as observer rather than participant.  She could see a wedge of the block, extending back into her distant past and forward into her all-too-short future.  Anything outside that wedge was invisible...  She found that it completely dissolved her anxiety about what might happen next.  Being not-present, the future couldn’t hurt her.  If pain lay ahead of her, it was as removed from her as her memories of a broken arm when she was twelve.  Neither one had any impact on the present as it slowly glided along, a moving flashlight beam following her footsteps through the wrecked cityscape.

 I found myself thinking about Mary and her peculiar forwards-and-backwards perception while I was reading physicist Sean Carroll's wonderful and mind-blowing book From Eternity to Here: A Quest for the Ultimate Theory of Time, which looks at the puzzling conundrum of what physicists call time's arrow -- why, when virtually all physical laws are time-reversible, there is a clear directionality to our perceptions of the universe.  A classic example is the motion of billiard balls on a table.  Each ball's individual motion is completely time-reversible (at least if you discount friction with the table); if you filmed a ball rolling and bouncing off a bumper, then ran the recording backwards, it would be impossible to tell which was the original video and which was the reversed one.  The laws of motion make no differentiation between time running forward and time running backward.

But.

If you played a video of the initial break of the balls at the beginning of the game, then ran the recording backwards -- showing the balls rolling around and after a moment, assembling themselves back into a perfect triangle -- it would be blatantly obvious which was the reversed video.  The difference, Carroll explains, is entropy, which is a measure of the number of possible ways a system can exist and be indistinguishable on the macro level.  What I mean by this is that the racked balls are in a low-entropy state; there aren't that many ways you can assemble fifteen balls into a perfect equilateral triangle.  On the other hand, after the break, with the balls scattered around the table seemingly at random -- there are nearly an infinite number of ways you can have the balls arranged that would be more or less indistinguishable, in the sense that any of them would be equally likely to occur following the break.  Given photographs of thousands of different positions, not even Commander Data could determine which one was the pic taken immediately after the balls stopped moving.

Sure, it's possible you could get all the balls rolling in such a way that they would come to rest reassembled into a perfect triangle.  It's just extremely unlikely.  The increase in entropy, it seems, is based on what will probably happen.  There are so many high-entropy states and so few low-entropy states that if you start with a low-entropy arrangement, the chances are it will evolve over time into a high-entropy one.  The result is that it is (very) strongly statistically favored that entropy increases over time.  

The Arrow of Time by artist benpva16 [Image licensed under the Creative Commons Creative Commons BY-NC-ND 3.0 license: creativecommons.org/licenses/b…]

The part of the book that I am still trying to parse is chapter nine, "Information and Life," where he ties the physical arrow of time (an example of which I described above) with the psychological arrow of time.  Why can't we all do what Mary Hansard can do -- see the past and future both -- if the only thing that keeps us knowing which way is forward and which way is backward is the probability of a state's evolution?  After all, there are plenty of cases where entropy can locally go down; a seed growing into a tree, for example.  (This only occurs because of a constant input of energy; contrary to what creationists would have you believe, the Second Law of Thermodynamics doesn't disprove evolution, because living things are open systems and require an energy source.  Turn off the Sun, and entropy would increase fast.)

So if entropy actually explains the psychological arrow of time, why can I remember events where entropy went down -- such as yesterday, when I took a lump of clay and fashioned it into a sculpture?

Carroll's explanation kind of made my mind blow up.  He says that our memories themselves aren't real reflections of the past; they're a state of objects in our environment and neural firings in our brain in the present that we then assemble into a picture of what we think the past was, based on our assumption that entropy was lower in the past than it is now.  He writes:

So let's imagine you have in your possession something you think of as a reliable record of the past: for example, a photograph taken of your tenth birthday party.  You might say to yourself, "I can be confident that I was wearing a red shirt at my tenth birthday party, because this photograph of that event shows me wearing a red shirt."...

[Is] the present macrostate including the photo... enough to conclude with confidence that we were really wearing a red shirt at our tenth birthday party?

Not even close.  We tend to think that [it is], without really worrying about the details too much as we get through our lives.  Roughly speaking, we figure that a photograph like that is a highly specific arrangement of its constituent molecules.  (Likewise for a memory in our brain of the same event.)  It's not as if those molecules are just going to randomly assemble themselves into the form of that particular photo -- that's astronomically unlikely.  If, however, there really was an event in the past corresponding to the image portrayed in the photo, and someone was there with a camera, then the existence of the photo becomes relatively likely.  It's therefore very reasonable to conclude that the birthday party really did happen in the way seen in the photo.

All of those statements are reasonable, but the problem is that they are not nearly enough to justify the final conclusion...  Yes, the photograph is a very specific and unlikely arrangement of molecules.  However, the story we are telling to "explain" it -- an elaborate reconstruction of the past, involving birthday parties and cameras and photographs surviving essentially undisturbed to the present day -- is even less likely than the photo all by itself...

Think of it this way: You would never think to appeal to some elaborate story in the future to explain the existence of a particular artifact in the present.  If we ask about the future of our birthday photo, we might have some plans to frame it or whatnot, but we'll have to admit to a great deal of uncertainty -- we could lose it, it could fall into a puddle and decay, or it could burn in a fire.  Those are all perfectly plausible extrapolations of the present state into the future, even with the specific anchor point provided by the photo here in the present.  So why are we so confident about what the photo implies concerning the past?

The answer, he says, is that we're relying on probability and the likelihood that the past had lower entropy -- in other words, that the photo didn't come from some random collision of molecules, just as our surmise about the billiard balls' past came from the fact that a perfect triangular arrangement is way less likely than a random one.  All we have, Carroll says, is our knowledge of the present; everything else is an inference.  In every present moment, our reconstruction of the past is a dream, pieced together using whatever we're experiencing at the time.

So maybe we're not as different from Mary Hansard, with her moving flashlight beam gliding along and spotlighting the present, as I'd thought.

Mind = blown.

I'm still not completely convinced I'm understanding all the subtleties in Carroll's arguments, but I get enough of it that I've been thinking about it ever since I put the book down.  But in any case, I'd better wrap this up, because...

... I'm running short on time.

****************************************

Sending pucks to Bolivia

Over the last few days I've been reading physicist Sean Carroll's wonderful book Something Deeply Hidden, which is about quantum physics, and although a lot of it (so far) is at least familiar to me in passing, he has a way of explaining things that is both direct and simultaneously completely mind-blowing.

I'm thinking especially of the bit I read last night, about the fact that even the physicists are unsure what quantum mechanics is really describing.  It's not that it doesn't work; the model has been tested every different way you can think of (and probably ones neither one of us would have thought of), and it's passed every test, often to levels of precision other realms of physics can only dream of.  The equations work; there's no doubt about that.  But what is it, exactly, that they're describing?

Here's the analogy he uses.  Suppose there was some physicist who was able to program a computer with all of Newton's laws of motion and the other equations of macroscopic physics that have been developed since Newton's time.  So if you wanted to know anything about the position, velocity, momentum, or energy of an object, all you have to do is input the starting conditions, and the computer will spit out the final state after any given amount of time elapsed.

A simple example: a cannon fires a cannonball with an initial velocity of 150 m/s at an incline of 45 degrees.  The (constant) acceleration due to gravity is -9.8 m/s^2 (the negative sign is because the acceleration vector points downward).  Ignoring air resistance, what is the highest point in its trajectory?

And the computer spits out 574.4 meters.

Now, anyone who took high school physics could figure this out with a few calculations.  But the point Carroll makes is this: could someone input numbers like that into the software, and get an output number, without having any clue what the model is actually doing?

The answer, of course, is yes.  You might even know what the different variables mean, and know that your answer is "maximum height of the cannonball," and that when you check, the answer is right.  But as far as knowing why it works, or even what's happening in the system that makes it work, you wouldn't have any idea.

That's the situation we're in with quantum physics.

And of course, quantum physics is a hell of a lot less intuitive than Newtonian mechanics.  I think the piece if it that always boggles me the most is the probabilistic nature of matter and energy on the submicroscopic level.  

Let me give you an example, analogous to the cannonball problem.  Given a certain set of conditions, what is the position of an electron?

The answer -- which, to reiterate, has been confirmed experimentally countless times -- is that prior to observation, the electron kind of isn't anywhere in particular.  Or it's kind everywhere at once, which amounts to the same thing.  Electrons -- and all other forms of matter and energy -- are actually fields of probabilities.  You can calculate those probabilities to as many decimal places as you like, and it gives phenomenally accurate predictions.  (In fact, the equations describing those probabilities have a load of real-world applications, including semiconductors, microchips, and lasers.)  But even so, there's no doubt that it's weird.  Let's say you repeatedly measure electron positions hundreds or thousands of times, and plot those points on a graph.  The results conform perfectly to Schrödinger's wave equation, the founding principle of quantum physics.  But each individual measurement is completely uncertain.  Prior to measurement, the electron really is just a smeared-out field of probabilities; after measurement, it's localized to one specific place.

Now, let me point out something that this isn't saying.  Quantum physics is not claiming that the electron actually is in a specific location, and we simply don't have enough information to know where.  This is not an issue of ignorance.  This was shown without any question by the famous double-slit experiment, where photons are shot through a pair of closely-spaced slits, and what you see at the detector on the other side is an interference pattern, as if the photons are acting like waves -- basically, going through both slits at the same time.  You can even shoot one photon at a time through the slits, and the detector (once again after many photons are launched through), still shows an interference pattern.  Now, change one thing: add another detector at each slit, so you know for sure which slit each photon went through.  When you do that, the interference pattern disappears.  The photons, apparently, aren't little packets of energy; they're spread-out fields of probabilities, and when they're moving they take all possible paths to get from point A to point B simultaneously.  If you don't observe its path, what you measure is the sum of all the possible paths the photon could have taken; only if you observe which slit it went through do you force it to take a single path.

It's as if when Wayne Gretzky winds up for a slap shot, the puck travels from his stick to the net taking every possible path, including getting there via Bolivia, unless you're following it with a high-speed camera -- if you do that, the puck only takes a single path.

[Image licensed under the Creative Commons Alexandre Gondran, 100 trajectories guided by the wave function, CC BY-SA 4.0]

If you're saying, "what the hell?" -- well, so do we all.  The most common interpretation of this -- called the Copenhagen interpretation, after the place it was dreamed up -- is that observing the electron "collapses the wave function," meaning that it forces the electron to condense into a single place described by a single path.  But this opens up all sorts of troublesome questions.  Why does observation have that effect?  What counts as an observer?  Does it have to be a sentient being?  If a photon lands on the retina of a cat, does its wave function collapse?  What if the photon is absorbed by a rock?  Most importantly -- what is actually happening that makes the wave function collapse in the first place?

To add to the mystery, there's also the Heisenberg uncertainty principle, which states that for certain pairs of variables -- most famously, position and velocity -- you can't know both of them to high precision at the same time.  The more you know about a particle's position, the less you can know even theoretically about its velocity.  Or, more accurately, if you pinpoint a particle's position, its velocity can only be described as a wide field of probabilities.  And vice versa.

I think the passage in Carroll's book that made me the most astonished was the following summation of all this:

Classical [Newtonian] mechanics offers a clear and unambiguous relationship between what we see and what the theory describes.  Quantum mechanics, for all its successes, offers no such thing.  The enigma at the heart of quantum reality can be summed up in a simple motto: what we see when we look at the world seems to be fundamentally different from what actually is.

So.  Yeah.  You can see why I was kind of wide-eyed, and I'm not even a quarter of the way through the book yet.  

Anyhow, maybe we should lighten things up by ending with my favorite joke.

Schrödinger and Heisenberg are out for a drive, with Heisenberg at the wheel.  After a while, they get pulled over by a cop.

The cop says to Heisenberg, "Do you have any idea how fast you were going?"

Heisenberg replies, "No, but I know exactly where I am."

The cop says, "You were going 85 miles an hour!"

Heisenberg throws his hands up and the air and says, "Great!  Now I'm lost!"

The cop by this time is getting pissed off, and says, "Fine, if you're going to be a smartass, I'm gonna search your car."  So he opens the trunk, and in the trunk is a dead cat.

The cop says, "Did you know there's a dead cat in your trunk?"

Schrödinger says, "Well, there is now."

Thanks.  You've been a great audience.  I'll be here all week.

**************************************

Breaking the world in two

It's no revelation to regular readers of Skeptophilia that I'm fascinated with quantum physics.

In fact, some years ago I was in the car with my younger son, then about 17, and we were discussing the difference between the Many-Worlds and the Copenhagen Interpretation of the collapse of the wave function (as one does), and he said something that led to my writing my time-travel novel, Lock & Key: "What if there was a place that kept track of all the possible outcomes, for every decision anyone makes?"

And thus was born the Library of Possibilities, and its foul-mouthed, Kurt-Cobain-worshiping Head Librarian, Archibald Fischer.

The Many-Worlds Interpretation -- which, put simply, surmises that at every point where any decision could have gone two or more ways, the universe splits -- has always fascinated me, but at the same point, it does seem to fall into Wolfgang Pauli's category of "not even wrong."  It's not falsifiable, because at every bifurcation, the two universes become effectively walled off from each other, so we wouldn't be able to prove or disprove the claim either way.  (This hasn't stopped fiction writers like me from capitalizing on the possibility of jumping from one to the other; this trope has been the basis of dozens of plot lines in Star Trek alone, where Geordi LaForge was constantly having to rescue crew members who fell through a rip in the space-time continuum.)

So it was with great curiosity that I read an article written by physicist Sean Carroll that appeared in Literary Hub last week, that looks at the possible outcome in our own universe if Many-Worlds turns out to be true -- and a way to use quantum mechanics as a basis for making choices.

[Image is in the Public Domain]

Carroll writes:

[Keep in mind] the importance of treating individuals on different branches of the wave function as distinct persons, even if they descended from the same individual in the past.  There is an important asymmetry between how we think about “our future” versus “our past” in Many-Worlds, which ultimately can be attributed to the low-entropy condition of our early universe. 

Any one individual can trace their lives backward in a unique person, but going forward in time we will branch into multiple people.  There is not one future self that is picked out as "really you," and it’s equally true that there is no one person constituted by all of those future individuals.  They are separate, as much as identical twins are distinct people, despite descending from a single zygote. 

We might care about what happens to the versions of ourselves who live on other branches, but it’s not sensible to think of them as "us."

Carrol's point is whether, if you buy Many-Worlds, we should concern ourselves with the consequences of our decisions.  After all, if every possible outcome happens in some universe somewhere -- if everything that can happen, will happen -- then the net result of our decision-making is exactly zero.  If in this branch, you make the decision to rob a bank, and in the other, you decide not to, this is precisely the same outcome as if you decided not to in this branch and your counterpart decided to go through with the robbery in the other one.  But as Carroll points out, while it doesn't make any overall difference if you take into account every possible universe, that's a perspective none of us actually have.  Your decision in this branch does matter to you (well, at least I hope it does), and it certainly has consequences for your future in the universe you inhabit -- as well as restricting what choices are available to you for later decision-making.

 If you'd like to play a little with the idea of Many-Worlds, you can turn your decision-making over to a purely quantum process via an app for iPhones called "Universe Splitter."  You ask the app a two-option question -- Carroll's example is, "Should I have pepperoni or sausage on my pizza tonight?" -- and the app sends a signal to a physics lab in Switzerland, where a photon is sent through a beam-splitter with detectors on either side.  If the photon goes to the left, you're told to go with option 1 (pepperoni), and if to the right, option 2 (sausage).  So here, as in the famous Schrödinger's Cat thought experiment, the outcome is decided by the actual collapse of an actual wave function, and if you buy Many-Worlds, you've now chopped the universe in two because of your choice of pizza toppings.

What I wonder about, though, is that after you get the results, the decision-making isn't over; you've just added one more step.  Once you get the results, you have to decide whether or not to abide by them, so once again you've split the universe (into "abide by the decision" and "don't" branches).  How many of us have put a decision up to a flip of the coin, then when the results come in, think, "That's not the outcome I wanted" and flip the coin again?  What's always bothered me about Many-Worlds is that it's an embarrassment of riches.  We're constantly engaging in situations that could go one of two or more ways, so within moments, the number of possible outcomes in the entire universe becomes essentially infinite.  Physicists tend to be (rightly) suspicious of infinities, and this by itself makes me dubious about Many-Worlds.  (I deliberately glossed over this point in Lock & Key, and implied that all human choices could be catalogued in a library -- albeit a very, very large one.  That may be the single biggest whopper I've told in any of my fiction, even though as a speculative fiction writer my stock in trade is playing fast-and-loose with the universe as it is.)

Carroll is fully aware of how bizarre the outcome of Many-Worlds is, even though (by my understanding) he appears to be in favor of that interpretation over the seemingly-arbitrary Copenhagen Interpretation.  He says -- and this quote seems as fitting a place to stop as any:

Even for the most battle-hardened quantum physicist, one must admit that this sounds ludicrous.  But it’s the most straightforward reading of our best understanding of quantum mechanics.   

The question naturally arises: What should we do about it?  If the real world is truly this radically different from the world of our everyday experience, does this have any implications for how we live our lives?

Largely—no. To each individual on some branch of the wave function, life goes on just as if they lived in a single world with truly stochastic quantum events...  As counterintuitive as Many-Worlds might seem, at the end of the day it doesn’t really change how we should go through our lives.

********************************

This week's Skeptophilia book recommendation is by the team of Mark Carwardine and the brilliant author of The Hitchhiker's Guide to the Galaxy, the late Douglas Adams.  Called Last Chance to See, it's about a round-the-world trip the two took to see the last populations of some of the world's most severely endangered animals, including the Rodrigues Fruit Bat, the Mountain Gorilla, the Aye-Aye, and the Komodo Dragon.  It's fascinating, entertaining, and sad, as Adams and Carwardine take an unflinching look at the devastation being wrought on the world's ecosystems by humans.

But it should be required reading for anyone interested in ecology, the environment, and the animal kingdom. Lucid, often funny, always eye-opening, Last Chance to See will give you a lens into the plight of some of the world's rarest species -- before they're gone forever.

[Note: if you purchase this book using the image/link below, part of the proceeds goes to support Skeptophilia!]