"I don't accept that you have to resort to animal experiments for explanation."
"But no real animals are involved, let alone harmed! It's an example to reason through, a thought experiment."
"I don't like your thinking. It's unnecessary, not to mention cruel and unusual. There's nothing reasonable about putting a cat in a box with a vial of poison and a lump of radioactive material, then wondering whether it's dead, alive or caught in some weird zombie state between the two, further prolonging its torment by pondering the philosophical meaning of it all instead of opening the damned box and rescuing the poor cat! Thinking it is not much better. I'm sure Mr Schrödinger–"
"Professor. Professor Erwin Schrödinger." OK, that didn't help. Jen's glare confirms it. The argument is slipping away from me. Not that it's supposed to be an argument.
Jen came round an hour ago for what's becoming our ritual end of weekend wind-down. Sunday night in after Friday and Saturday — and probably Thursday — nights out. Beer, pizza, TV and my flat to ourselves.
"Nice T-shirt," she said when I opened the front door. "What does it mean?"
Wanted Dead and Alive – Schrödinger's Cat is a favourite of mine, and this kind of geeky T-shirt has become my trademark in the physics department. I guess Jen hadn't seen this one before. A sure way to kill a joke is to explain it, but not explaining would be worse — apparent elitism, a sure-fire romance killer.
The discussion started out well enough. I managed to talk around subatomic particles and metaphor my way through wave functions without Jen's eyes glazing over. Quantum mechanics is now, however, threatening the evening, having somehow picked a fight with ethics and animal rights. Beer on empty stomachs is doing little to bridge the art–science divide.
"I'm sure he could have come up with something more humane to make his point," Jen continues.
"The fact it's a cat is not important–"
I'm boxed in and more in need of rescue than any gedanken cat.
The doorbell goes.
"Ooh, pizza!" Jen's mood has found new prey.
"I'll get it."
They're quick tonight — I'm only halfway through my second beer. I ordered the pizza en route to the fridge for more bottles. I grab some cash, go downstairs and return, pizza in hand, as the scooter whines off into the night.
"What did you order?"
"A large one, for sharing."
"Well, duh. What kind?"
I pause. Pick up the conversation again or let it go?
"Schrödinger's pizza." Clearly something within me favours the risky option. "The box is closed and you can't tell exactly what's inside, right? It's pizza, and smells generically of pizza, but you can't be sure of the topping. You're probably wondering whether it's got pineapple or not. Maybe it does, maybe it doesn't. Fifty–fifty. What's the state of the box? Pineapple or no pineapple? Or both? Dead or alive, or dead and alive?"
I love pineapple on pizza. And the morning after, fresh from the fridge? Throw in coffee and sex and that has to be the perfect start to the day. For me. Jen prefers herbal tea and pizza without pineapple. Pizza in the morning is simply not on the menu. But the sex is good.
"If you loved me, you'd order without."
The L-word catches me off guard. Jen hasn't used it before. Not about us, not about me, not about anything — sex is sex, not making love. We've been playing around and playing along, having fun, nothing more. Just a summer thing, a summer fling. In September Jen is heading off to South America for a year and that'll be it. We both understand that... or I'd thought so. Neither of us has actually said as much. On the outside it's improv. But in this case I thought we were both sneakily reading from the same prepared script, no hidden variables.
"But I'm just the narrator! I'm outside the experiment."
"No you're not. And I'm not sure I appreciate being part of an experiment — although I guess it spares the cat... smart move." A smile. I'm not totally out of favour.
"You said earlier that this Schrödinger paradox raises the question of observer-created realities," Jen says. "As narrator, there's no question: you ordered the pizza; you created the reality. You know the outcome. The pineappleyness doesn't manifest itself one way or the other simply because I open the box."
"In theory, but I don't know if they got the order right. So at this point, like you, I guess I'm just an observer. The contents of the box are in a shimmering state of uncertainty, a superposition of different possibilities. Until we open the box, there's no better description of the pizza than simultaneously topped with pineapple and without. And, if you imagine these possibilities played out across parallel universes, there's one universe where the pizza has pineapple, another universe where it doesn't and–"
"Don't forget the universe where I thump you. In case you were wondering, teasing me with physics while withholding my half of the pizza, shrouding it with an air of undecided pineapple? Not a winner."
"But at least it's not pepperoni," I say, trying desperately to regain favour.
A couple of weeks after the end of the summer term, the pepperoni discussion had not gone well. But I guess it had helped clarify some things. We'd been in the kitchen, having a beer, thinking about getting a takeaway or seeing if Niall, my flatmate, had left anything useful in the freezer.
The doorbell rang.
"Who's that?" Jen asked.
"Don't know. I wasn't expecting anyone."
I went downstairs to find out and came rushing back up.
"It's a pizza delivery!"
"But we didn't order pizza."
"I know. It must be for one of the other flats. Hungry?" I grinned, grabbing some change.
"But it's not ours!"
"I know. It's probably for upstairs. And when it fails to turn up in half an hour, they'll ring up and get the free pizza they're entitled to for late delivery. It's win–win!"
"Hugh, you're bad," she called after me as I disappeared out the flat door.
"Pepperoni!" I returned in triumph, mischievous grin on face, pizza box in hand.
"I'm vegetarian," Jen replied.
I'd known that, but it hadn't really registered as something I needed to care about. That was about to change. "You could, err, pretend it was fish?"
"First, I'm not going to pretend. This isn't a case of being clever by being naughty. I'm not a vegetarian because someone else told me to be — it's my choice. Second, vegetarians don't eat fish."
"Some vegetarians do. Niall says he's vegetarian and he eats fish."
"People who eat fish are not vegetarians. Just because some of them say they are doesn't make it so. Mental hospitals are filled with people who claim to be Napoleon, Jesus and Elvis. Doesn't mean they are."
"You never know." I smiled. Jen glared. "OK, if they're not vegetarians and they're not omnivores, what are they?"
"Pescetarians or fishetarians, take your pick. Anyway, I saw Niall eating bacon the other morning."
"So what am I supposed to call him?"
Niall being away for the most of the summer is good for everyone.
I'm spending a lot of time in the lab at the moment, trying to get sensible results out of my current experiment. Low-temperature physics gives you easy access to helium, and where there's helium there's always squeaky-voiced fun to be had. The week after most undergrads had gone home, Niall had dropped by my end of the building for mid-morning coffee and downtime.
"Hi, I'm Jen," he squeaked. "I like Spanish, media studies, kittens and postgrads."
Anything in a Mickey Mouse voice is funny, even jealousy. Jen standing behind him as he did this? Priceless. Niall stumbled a high-pitched apology, a mockery that only dug him a deeper hole. Jen then suggested a sudden and intimate relationship between kittens and Niall she would be more than happy to arrange — one severely at odds with her moral stance this evening.
"Dead or alive?" I push the pizza box across the table to her.
"If it's pineapple, you're dead to me."
She opens the box, smiles, leans over and kisses me.
It's an eight-slice pizza. Four with pineapple, four without.
"I love you too," she whispers in my ear.