"But all of that just proves what I'm saying," Adam says. "I wouldn't conclude that the spiders intended to use the light to help trap the insects. I'd assume that I could never understand what the spiders were doing and why, because I'm not a spider."
"But scientists have to try to understand things. They have to ask why."
"Yes, but they'll never get a proper answer," Adam says.
"Anyway," I say, in a louder voice than I intended. "Er ... Anyway, I was just going to say that this stuff about science and language is really interesting in relation to something I read about the big bang. It's a bit complicated, but it shows that if you start with a few basic assumptions about the big bang, then logic takes you to a situation where we're either living in a multiverse, or a universe created by God. There's really no other option."
"My head's going to be wrecked by the end of tonight," says Heather.
"Just drink more wine," says Adam, smiling at her.
I've just finished the last piece of garlic bread and Heather and Adam have both put down their knives and forks. I pick up my bag and take out a packet of cigarettes.
"If you're into all this meditation, are you supposed to drink wine?" Heather asks.
"Oh, I do it very rarely," says Adam.
I don't know if he means meditation or drinking and although I expect Heather to ask him, she doesn't. Instead, she picks up a stray rocket leaf and puts it back in the salad bowl.
"Do you mind if I smoke?" I ask her.
"No, not at all. I'll open the back door though, if you don't mind."
She gets up to do that and Adam and I briefly start making movements towards clearing the table before she tells us not to fuss and just leave it all.
"No, come on," she says. "Tell me about this whole God-or-the-multiverse thing."
"OK," I say, lighting my cigarette. "Sorry—do you have some sort of ashtray? I can go outside if you want..."
"No, I'll get you a saucer."
"God or the multiverse," says Adam softly as Heather gets a saucer. "Hmm."
"Are you both familiar with basic quantum physics?" I say. "Not the really hardcore stuff, but the kind of thing you'd find in a popular science book. You know, the wavefunction and probability and that sort of thing."
Adam's shaking his head. Heather cocks her head to one side as if she's trying to make the information roll down a hill in her mind and come to rest in a place she can access it.
"I should know it," she says. "I think I did know it once. But you ignore all that stuff when you're working on the molecular level. It just doesn't have any perceivable effects so it can be disregarded."
"I'm afraid I'm completely in the dark," says Adam.
"OK, well in a nutshell—and I warn you, I'm doing a humanities Ph.D. so you could probably get this from a more reliable source—quantum physics deals with subatomic particles, in other words, particles that are smaller than atoms."
Adam now frowns. "Call me nuts, but I'm having this odd sensation as if I'd seen one of these particles once or something," he says. "Maybe I'm drunk. I must have learnt this at some point and then forgotten it. Anyway, despite all that, my brain is begging me to ask you: What on earth is smaller than an atom?"
"Oh, well, everyone knows that an atom is made up of neutrons, protons, and electrons," says Heather.
"And those parts are all made up of quarks," I say. "Apart from the electron, which is indivisible—or at least people think it is. People thought the atom was indivisible a hundred years ago, and before that they didn't think it existed, so it's not as if we know everything."
It's cold with the back door open; Heather gets up and takes a small cardigan from the back of a chair and puts it on.
"I think we're pretty sure about the electron," she says. "Brrr. It's cold."
Adam and I exchange a look.
"Anyway," I say, "quantum physics deals with those tiny particles of matter. But when physicists first began theorizing about these particles and observing them in action in particle accelerators and so on, they found out that the subatomic world doesn't act the way we'd expect."
"How?" asks Adam.
"All that common sense stuff—the past happening before the future, cause and effect, Newtonian physics, and Aristotelian poetics—none of it is applicable at a subatomic level. In a deterministic universe, which is the sort Newton thought we lived in, you can always tell what's going to happen next, if you have enough information about what went before. And you can always know things for sure. It's either day or night, for example: It's never both at once. On a quantum level, things don't make sense in that way."
"This is the stuff that does my head in," says Heather.
"Yeah, it's weird," I say. "It's like ... there are particles that can go through walls just like that. There are pairs of particles that seem to be connected and stay connected in some way even when they are separated by millions of miles. Einstein called it 'spooky action at a distance' and rejected it completely, as it seemed to suggest that information could travel faster than the speed of light."
"And nothing can travel faster than the speed of light," Heather says. "I'm with Einstein on that one."
"Anyway, one of the weirdest things about subatomic particles is that something peculiar happens when you observe them. Until they are observed, they exist in a smeared-out state of all possible positions in the atom: the superposition, or the wavefunction."
Adam's shaking his head. "You've lost me, I'm afraid," he says.
"OK," I say. "Imagine that you are out on a walk and I don't know where you are. You could be at the university, in the park, in the shop, in a spaceship, on Pluto, whatever. These are all possibilities, although some are more likely than others."
"All right," says Adam.
"Well, conventional logic tells us that you are definitely in one place or another, regardless of whether or not I've seen you there, or know for sure that you are there. You are somewhere, I just don't know where that is."
Adam's nodding and, for a second, I imagine a life so normal that I could be with someone like him, perhaps sharing a house like this, and have such a mundane, but somehow amazing, thought: Is he in the shop or is he at work?
"Anyway," I say, "obviously you're standing in for the particle in this example ... Well, quantum physics says that when your situation is unknown—so you could be in the shop or in the park for all I know—you actually exist in all places at once until someone finds out for sure by observing you. So instead of one clear 'reality,' there's a smear. You're in the shop and the park and the university, and it's only when I go out looking for you and see that you're in the park that all the other possibilities melt away and reality is set."
"So observation has an effect on reality?" says Adam.
"Yes—well, in this way of looking at it. This idea that all probabilities exist as a wavefunction until an external observer looks at—and therefore collapses—the wavefunction is called the Copenhagen interpretation."
"Are there other ways?"
"Yes. There's the many-worlds interpretation. In a nutshell, while the Copenhagen interpretation suggests that all probabilities collapse into one definite reality on observation, the many-worlds interpretation suggests that all the possibilities exists at once, but that each one has its own universe to go with it. So there are, literally, many worlds, each one with a tiny difference. So in one universe you're in the park and in another you're at work and in another you're on the moon, or at the zoo or wherever."