Chapter10E

Zoë, Tuesday 16th March, evening
The lecture notes begin in almost continuous prose and I can hear Richard's voice in it in a way that still spooks me out. From beyond the grave again.
Lecture 5 – Many Worlds (I wanted to call it “What the Cat Saw“)
The story so far:
- Very small things like sub-atomic particles are not just in one place or moving in one direction but smeared out into a blur in which multiple possibilities exist in parallel.
- When you “ask” them to behave as ordinary in-one-place-at-a-time particles, they do, randomly choosing one of the parallel possibilities of where they are – the other possibilities apparently vanish into nothing. This, it seems, is why the world we see does not look blurry and wavy (unless you're drunk), why we see things in only one place at a time.
- Our attempts to explain how particles know which kind of behaviour we are expecting of them have conspicuously got nowhere. Some physicists think that there is some limit to the size or complexity of systems which can be in a mixture of different states, but we have no evidence of this: particles interact in such a way as to form similarly ambiguous configurations (technically “superposed states”) of larger multi-particle systems – the phenomenon called quantum entanglement. There seems to be no limit to how far this can go.
- All we know is that the collapse of the wavefunction – the evaporation of the other could-have-been possibilities – happens before these parallel versions of reality impinge on human consciousness. The role of the human mind seems to challenge the objectivity of the world – surely we can't be creating reality by perceiving it? Schrödinger and Wigner invented paradoxes involving the reprehensible mistreatment of cats to illustrate the absurdity (as they saw it) of this idea.
This is getting a bit too much to keep track of in a “let's just have a look” frame of mind – I'm going to have to make a solo evening of it. I go to the corner shop to buy some alcohol, which seems important, and struck by a sudden impulse I come back with a half-bottle of JD, two litres of Coke and some candles. I'm not quite sure why candles, but they seem to belong to doing things properly. I put on a CD that a not-very-competent two-tone revival band gave me when we went to see them at the Derby Arms, mix a drink, light a few candles and then decide that they're a bit silly after all and put them out again.
Now I feel a little more ready for Richard's document. It goes on like this:
In the fifties a PhD student called Hugh Everett came up with a different explanation, which got little attention at the time but which has gradually gained credibility as we have come to understand it better and as various apparently more plausible alternatives have bitten the dust. Today opinion polls suggest it is the majority view among physicists.
It was to introduce Everett's idea that I asked you to imagine the world through the eyes of Schrödinger's cat.
ASK FOR REACTIONS – WHAT DO THEY RECKON THE CAT SEES?
I still have no idea what the cat sees – what the world looks like if you are alive and dead at the same time – despite the headaches I've given myself over the last ten days trying to solve the riddle.
At this point the continuous prose gives way to notes which are a bit harder to follow. There's a diagram labelled put this in presentation which consists of a sketch of a fairly normal cartoon cat and a sketch of a cartoon cat on its back with its legs in the air, with a sort of cloud in between them labelled form of equations says they can't interact. Underneath all this in big bold capitals there's the question WHY CAN'T THE LIVE CAT SEE THE DEAD CAT? I think about this for a while, trying to ignore the reference to equations as well as the fact that it involves dead cats. The number of things I have to ignore is getting larger than I like it to be.
What would it be like to be a living-dead cat in the blurry world of Richard's subatomic particles? I wonder about the analogy with split-brain patients I thought of yesterday: two minds in the same head, two cats in the same box... only here, for some highly abstract and theoretical reason involving equations, they are completely unaware of each other instead of just mildly surprised at each other's behaviour.
I pour some more whiskey and fizzy brown gunk into the glass and stare into it for a while as if I could expect to find inspiration in there, floating among the bubbles like an ice cube. That's a point – it needs ice. I go to the kitchen, where I'm quite impressed to find that the ice tray actually has ice in it. I even find a lemon and a knife sharp enough to slice it. The drink makes a nice clinking noise as I carry it back to my room. I'm sort of hiding from the others, Jasmine's going to be cross with me for not giving up the whole Richard-related investigation thing but I can't stop now when I feel so close to cracking it.
As I sit down I decide he did do the experiment on himself – if I can work out what he thought the live Richard was going to see maybe I'd understand why. Back to the however-many-zillion-dollar question then: why can't the live cat see the dead cat? Well probably because they can't interact, whatever that exactly means. Feeling a bit as if I'm cheating in an exam, I read on in the document for the answer, and find:
Entanglement (as far as sight is concerned, entanglement of the cat with the light reflected off it: the light that falls on the dead cat has only fallen on a dead cat from the dead cat's point of view).
I try to say that aloud and fail. Then I say “How much wood would a woodchuck chuck” several times and then stop suddenly, wondering if Jasmine can hear me – she'd take it as final proof that I've lost it and need to be forcibly restrained and prevented from reading any more of Richard's notes. I wonder how much of this booze I've drunk already – it depends how much of the JD that's missing from the bottle is still in the glass, and I can't really tell because of the Coke.
I try to remember what entanglement is. The pool game – the cue ball never bounces off the same way that the black goes. You can only get the right combinations, the possible combinations; the different parallel versions of the particles get linked together until you've got parallel versions of the whole cat. I take another gulp of my drink and kind of wish I'd got something else instead. I try rearranging Richard's sentence a few times until it makes more sense: the live cat can only see the version of reality where the cat is alive.
The next sentence says almost the same thing, so I must be on the right track: The live cat is only aware of the live cat, and the dead cat, of course, isn't aware of anything.
Wigner's friend opens the box – now he is entangled too. Wigner next.
I have to slow down and think it through again, and then I decide to take a break and check on Jasmine and Charlie. I wander back into the lounge where the music's turned down and they're talking quietly. They stop when I come in; Jasmine has a kind of reproachful look on her face.
“Zoë...”
“You thought I was going to give up all this nonsense.”
“Well...”
“Last attempt. I promise. Tomorrow I stop.”
Charlie is wearing the goofy grin that means he's about to roll yet another funny-shaped spliff. I give him a not now look and he gives me a go on, it'll do you good look. I'm starting to wonder why people bothered inventing speech. I can tell he's about to explain that I need to stop reading about theoretical physics before I turn into a dropout, and spend more time drinking alcohol and smoking weed like a good student. I'm sure there's something wrong with the logic of that but I'm not quite sure what it is, so I just say “I need to read this last thing, then that's it,” and go back into my room.
At least I've got the alcohol. Right then. So we have these two parallel versions of reality starting with tiny particles and gradually entangling more and more things into their side-by-side existences until we have simultaneous parallel versions of a cat and eventually of two presumably-mad scientists, unaware of each other's existence. I read on.
And so on – ever more of the world entangled into parallel realities. The way the idea is usually presented: the universe splits into two parallel worlds whenever an event has two possible outcomes.
Implies all “would-have-been” worlds are still there (e.g. where Germany won WWII or where dinosaurs are still alive), we just can't see them (like the cat).
This sounds more like the kind of thing I expected from Mysteries in Physics, and I start to get the feeling that this business with electrons and mystical cats is finally starting to get somewhere, to reconnect with ideas I can cope with. It's a bit mean of him to spend so long on electrons and leave all the cool stuff until the end though. Not to mention shooting himself before giving the lecture that he's left all the cool stuff to. It occurs to me that these carefully-prepared notes represent a hell of a lot of work for someone who's going to shoot himself – though not necessarily for someone who's about to play a quantum-blurry-random version of Russian roulette, perhaps?
Actually truer to say it's the observer that splits, not the universe – becomes two people who each see only “their own” (entangled) aspects of reality.
I think about this for a while, and about what it means for one person to become two people – the split-brain analogy again. Then hear Jasmine and Charlie giggling and suddenly feel lonely, sitting here on my own at the mercy of the astonishing idea I can feel gradually creeping up on me. I decide to take another break.
In the lounge I see what they're giggling at: Charlie's mixing his weed with some kind of herbal smoking mixture apparently meant for the benefit of cannabis smokers who don't want to do tobacco – Jasmine, I assume, as Charlie smokes like a defective industrial chimney – which is made somewhere in east Asia and goes by the remarkable name of Poof Dragon. They've got the rest of the set of felt tips that the orange one came out of and they're drawing very camp pink dragons and laughing a lot. Jasmine's have long eyelashes and lipstick and Charlie's have moustaches and what appear to be tight leather trousers, only it's a bit hard to tell on a dragon.
I suddenly wish I could forget about Richard and wacky physics theories and just laugh about pink dragons with my friends. I almost manage it – I sit down with them and draw my own dragon with pouting lips done in a different shade of pink, and we have a giggle about it and feel all warm and loving, and then I catch a glint in Jasmine's eye that says we've finally got her away from that obsession and I remember the feeling of being nearly there and have to go back to the document.
“Oh Zoë, it's not doing you any good!” says Jasmine.
I assure her that this is the last bit and she says “but that's what you said last time” before reluctantly letting me go back and carry on.
I change the music: it's really not very good, and another album of spacey dub seems more appropriate.
I try to visualise the branching streams of human consciousness winding through a universe of multiple possible realities, which I imagine like an illustration in a kids' encyclopaedia with little pictures of dinosaurs and Hitler standing among forking coloured ribbons.
The notes continue – fortunately we're back to the stuff where he's planned the exact wording:
This is Everett's idea – there is no collapse of the wavefunction, just a separation of the different outcomes and with them the observers that perceive them. It's known as the many-worlds interpretation, a slightly unfortunate name as it has led many people to the knee-jerk reaction that this is all simply too far-fetched.
Then there's some complicated explanation of why this is actually a simpler, more Ockham's-Razor-friendly idea than any alternative, but I reckon I'll take his word for it. Instead I close my eyes, trying to visualise all the concepts Richard talked about on the course instead of making any further effort to understand the details. Inside my eyelids, blurred particles in several places at once entangle cats and people into their parallel realities, oblivious of each other... each imagines that the others don't exist when they've just gone out of view. It kind of makes sense – reality as a multidimensional maze where all the would-have-beens and could-have-beens are other turnings that we haven't taken. It's not exactly a completely unfamiliar idea, but it's a fairly dizzying one when you really think about it. Scary – a universe littered with evil dictators and ravenous monsters you thought were all safely dead.
Is another version of Richard still alive in a parallel world, with a Zoë who has no idea about all of this? I suddenly realise who the other Zoës are and open my eyes.
It takes a second or so for my sight to focus back on the screen. For a moment I think that's the end of the document, but as I scroll down a last page comes into view, once again in the form of a continuous script. And this, if I can make sense of it, could be the last jigsaw piece I'm looking for – it's headed The Quantum Suicide Experiment.
One of the most important criteria that a scientific theory must fulfil is that of falsifiability. It must be possible, in principle, to tell if the theory is wrong – otherwise we can never have any evidence that it is probably right. A theory gains credibility by surviving attempts to disprove it. Critics of the many-worlds interpretation often claim that it is not falsifiable – that we can never know if there are parallel worlds irrevocably separated from our own, because we simply couldn't tell the difference if there were.
There is, however, an experiment that a scientist who doesn't care about his or her own survival could do to find out whether or not the many-worlds interpretation is correct. That is to put himself (or herself) in the position of Schrödinger's cat. Imagine an apparatus in which a quantum event with a 50% probability triggers a shotgun, blowing the experimenter's brains out.
I feel a bit wobbly and upset again – I don't need to do much imagining here, and I wish I did. Instead I do my best to turn my imagination to Richard presenting this lecture in some parallel world – he'd pause for dramatic effect, and his students (myself, or my “sister“, among them) would no doubt think he was rather cool and he'd feel all smug. They would of course have no idea he's already done the experiment he's talking about, or they'd run a mile.
Imagine he can arrange the experiment so that his death is instantaneous. If the many-worlds interpretation is correct, the scientist will survive in one world and die unaware of the outcome in another. To put it another way, one of the scientist's two future selves is alive, the other dead. Like the cat, the live experimenter is unaware of the dead one, and the dead experimenter is of course unaware of anything. From the point of view of our scientist's only surviving future self, nothing has happened. Of course, that could – from his point of view – be by chance. However, he can repeat the experiment as many times as he likes. If he does it seven times, he has less than a one per cent chance of survival according to the conventional view of the universe. If he repeats the experiment thirty times, the chances are less than one in a billion. If the many-worlds interpretation is correct, however, one of his future selves will always be alive, unaware of what has happened in other worlds. His apparently miraculous survival against odds of a billion or a trillion to one would be very strong evidence that the many worlds are in fact real.
So should we hope that some scientist one day, perhaps someone who is terminally ill, will put his own life on the line to discover the truth? Unfortunately, although it will arguably answer the question from his or her own point of view it will do nothing to inform the rest of us. The overwhelming majority of our future selves will live in worlds where the experimenter dies – or to put it in terms of our instinctive understanding of the world, anyone who does this experiment will almost certainly die without leaving any record of any useful findings. It is only the experimenter in the single world in which he remains alive, from our point of view corresponding to a very tiny probability, who will know for sure. Of course, every one of us has a future self in his low-probability world too – what will they think? Well, from their point of view, what has happened is just an immense coincidence. And ultimately, they would be extremely unlikely to believe him if he told them the truth. I know I wouldn't.
I've nearly got to the end of the document and I'm still not convinced that what I've got so far explains Richard's death. So the biggest mystery in physics is something that you can answer with a simple experiment, with the catch that if the theory's wrong you die, and even if it's right you die from everyone else's point of view apart from their alter egos in your highly improbable world. And here's a physicist who's terminally ill, so he's got nothing to lose.
So far and taken at face value, it makes sense in a kind of barely-logical way but doesn't quite ring true – unless there's something very very powerful about scientific curiosity that I just don't get, I can't imagine it being reason enough to shoot yourself in the head. I can imagine him years ago deciding he'd do the experiment if he ever happened to find himself terminally ill, as he seems to be implying in that letter to Colin, but I can't imagine him going through with it when he actually was. That's the kind of unsatisfactory answer you expect in an Agatha Christie novel, not in real life.
How about a more psychological explanation: if he was desperate and wanted to end it all anyway but needed an excuse to justify it to himself, what better way than pretending he's doing it in the name of science? But he didn't seem desperate at all – far from it, he seemed more like he'd won the lottery.
Or another one: I think again about the quantum suicide experiment, the forking streams of reality, the state of mind of a dying man, and all this talk of immortality, and wonder if the truth can really be as outlandish as what this all seems to add up to. I'm beginning to think I can see what he meant in one of the weirder sentences of his letter to Colin: My motives aren't really all that noble or philosophical; to be frank I'm more interested in the possibility it raises that everybody's favourite dream of the supernatural is actually, in its own peculiar way, reality.
I scroll down to the last section of the document – and this, at last, seems to be what I should be looking at. The heading is Quantum Immortality.