Perpendicularity

The post-box asked me how I was feeling, and commented that I had a slightly-elevated temperature.  I thanked it, and walked off feeling a little disconcerted.  Then the fire hydrant on the corner, where I paused to wait for the traffic to clear before crossing, called me things I'd rather not write down and assured me that a place in Hell was being reserved for me even now.  I asked it, politely, if it meant the Norwegian town, and it cackled with delighted laughter.  After I'd crossed the street I dug my mobile phone out of my pocket and called my psychotherapist.
"Dr. Fraud's not available right now," said his receptionist, a pleasant young man with a fear of teeth.  My sister had dated him for a few weeks until he admitted that the only way they could have a relationship was if she had all her teeth removed and wore dentures, but not when he was around.  She gave it serious consideration before dumping him, so I was reasonably certain he was a nice guy.  "He's... well, since it's you, he's screaming in German about squirrels and keeps hitting his desk with a broom.  He's got a three o'clock with a near-catatonic, and that always calms him down, so I'd call back after four."
I thanked him and hung up.  I wasn't really sure that a session with Dr. Fraud would make me saner, but it would certainly make me feel saner.  Even while the urban furniture talked to me and commented on my health and future.
I arrived at the university about twenty minutes early and found the rest of my physics class in the coffee-hall.  The architect who'd designed the campus could clearly remember his student days well as there was a coffee-hall, a beer-hall, six lecture-halls and a Mensa rumoured to be capable of seating the entire university, albeit over seven floors, if it needed to.  My group were sitting by the windows that looked out onto Anneliese Quad, near coffee-station six where they served specialty coffees and the baristas hand-selected blends and beans.  I ordered the latest Kenya single-estate, black, no sugar; and sipping its slightly fruity, earthy liquid, sat down next to John.  He grinned at me, and dropped a text-book into my lap.
"Ouch!  Watch it, muffmonkey!"
"Yeah, you too Mr. Handcuffs," he said.  "Look what chapter we're up to."
I put my coffee down, carefully out of John's reach, and turned to the bookmarked page.  'Perpendicular AIs' I read.  "What're they then?"
"Don't you ever do the pre-lecture reading?"
"Not when I've got you to do it for me."
"Hah!  I should completely tell you the wrong thing now, so you can look stupid in front of Professor Clerihew.  It's all about... chickens!  Purple chickens, that they breed in the Large Hadron Collider so that they can have eggs that are poached forty minutes before they're laid.  The chickens are too heavy to escape of course, because they have a diet of Higgs Bosons."
"Yeah, very funny.  Purple like your sister's rug?"
"Oh the shame!"  John's eyes twinkled.  "My sister's far too proletarian to look after herself like that.  It gets mown once a year at Easter; at any other time I leave a machete by her bedroom door for would-be explorers."
I laughed, despite myself.  "So what are perpendicular AIs then?"
"Hah, that's the thing, no-one really knows any more."
"Any more?  They knew once then?"
"Sort of.  You know that we've located nine dimensions so far?"
"Yes, that was the first week of lectures, pinhead.  They're numbered from -1 to 7 and we all pretend that was deliberate and not a cock-up."
"Yeah, well, about twenty-years ago they were doing some experiments with computers to see if they could discharge heat into one of the other dimensions.  The idea was that if the heat could all be dissipated into a different dimension then you could improve the efficiency of chips and circuits, although you'd still run into the quantum barrier at some point.  So they're building these chips with these odds little fins on them that cross the dimensional barriers, which they can do at microscopic scales but no larger."
"Like now," I said, knowing John hated to be interrupted.  He glared at me, I sipped my coffee and pretended to be innocent.
"Yeah.  Well, that's kind of because we stopped trying.  The computers with these chips with their special fins... they somehow slipped through the dimensions altogether and disappeared."
"Disappeared?"
"Yeah, I don't quite get it, but Clerihew might explain it in the lecture.  I can ask him if he doesn't."
"So what happened to these computers then?"
"Well, at first we thought they were just gone, but then they started connecting up to computers in our dimensions.  It was kind of hard to work out what happened, but there's now a branch of cross-dimensional mathematics that gets used to do it.  The computers were still working in this other dimension, and they could connect to our dimension.  At first it was just computers, but then they started connecting to like, everyday objects.  Fridges, and toasters, and dolls.  And they'd seem to start talking to people, only no-one believed them at first.  And they went a bit odd, which might be because all dimensions are at right-angles to each other, but I don't know how that's supposed to work either."
"A fire hydrant spoke to me on the way here," I said quietly, putting my coffee down.  John looked at me hard, trying to work out if I was joking or not.
"Just a fire hydrant?" he said, sounding like he was about to start laughing.
"And a post-box.  It said I was running a temperature and asked me how I was."
"Oh crap."  John just looked at me.  Everyone around us starting packing up and standing up to go to the lecture.  "I think we'd better try and catch Clerihew before the lecture then," he said.  "It sounds like you witnessed the start of an incursion."