My mate Ed has been working on a new project for the last week or so. He hasn't done the classic "never comes out for food or sleep" routine, because, unlike all those other scientists in the movies, he isn't an idiot. But he did keep the basement door locked (where our workshop is), and he did refuse to tell me what he was doing. Ed has done this before. Usually the results, though utterly, utterly useless, make great conversation pieces, but sometimes they are explosive or, on one memorable occasion, sentient, so I was in two minds about what to expect this morning when he announced that he was done, and asked me down into the basement to show me.

I couldn't see anything new in there except for a single, one-inch long component rocker switch in the middle of the otherwise empty worktop. It had a red wire and a black wire soldered to the contacts underneath, trailing off the table into some dark corner of the lab. Ed was sitting in a chair at the worktop, with the switch under one hand and a stopwatch in the other. As I descended the stairs I saw him turn the switch on and start the stopwatch simultaneously. He counted to five and then turned it off, before he looked up.

"Is that all of it?" I asked, sitting in the chair opposite him.

"Yes," said Ed bluntly, smiling broadly at me. There was a pause. I was half-inclined to believe him. Ed is the kind of guy with whom, after a while, you learn to take nothing for granted. But he shook his head and continued, "No, this switch is connected to one of Jazz's network ports." He nodded at Jazz, the extremely ancient Acorn personal computer that has been sitting in the corner of our basement for the last four or five years. "As you know, Jazz's other network port runs directly into the university data network. That network has a large number of other computers on it, including among other things a pair of Cray supercomputers that serve the Theoretical Physics labs..."

I know all this already, and Ed knows I know. Most of his projects begin with a speech exactly like this, right up to "Theoretical Physics labs".

"Now the Crays, as you are probably not aware (unless, like me, you are updated on a minute-to-minute basis of the status of the experiments currently in operation in the Theoretical Physics Centre), are even as I speak involved in running and processing the data from a ground-breaking experiment in a region of physics known as quantum tunnelling. Now, as I recently realised, quantum tunnelling is not all that different from the phenomenon called teleportation..."

I hold up a hand. "Let me guess the rest. You've got some kind of program stored on Jazz. When you close the switch, that's the cue for it to transfer itself all the way over to the Crays, where it forcibly takes over the experiment."

"You have learned well. Yeah, it aborts the experiment currently in progress, and then begins its own sequence of instructions. When I open the switch again, the program ceases and everything goes back to normal."

I nod approvingly. I long ago made the point to Ed that doing bad things to other people's expensive laboratory equipment was not very nice. "So what does the program actually do?"

Ed waves his hands vaguely. "Teleports stuff. It's a bit complicated."

"I saw you already closed the switch."

Ed winks, and checks his stopwatch. "That was one minute and thirty-one seconds ago. Why don't we take a walk outside? The results won't be visible for a few minutes."

"The results will be visible from the street?"

"You'll see. Or not."

Cryptic. Ed takes the stopwatch with him as we head up to the front door. He locks it and we walk out into the suburban street. There is no traffic about but there are a few people going about their business. It's a beautiful day, the sun is shining and it's almost noon.

"You're not gonna blow the whole world up, are you?" I ask Ed. This is not a dumb question. Ed flirts with Armageddon practically on a monthly basis. It's all rather worrying.

"No, nononono. Nothing like that. Something rather more spectacular."

I point at a dark building on the horizon and say, "TPC's that way." I'm still half-expecting some kind of explosion.

Ed shrugs. There's a long pause while we wait under one of the trees that line this street. I sit down on the pavement and enjoy the sunshine. Ed intently studies his stopwatch. We wait for at least five minutes. Nothing happens. I point this out to Ed.

"It'll happen, it'll happen," said Ed. "What's the speed of light these days?"

"Uh... Two hundred and ninety-nine million, seven hundred and ninety-two thousand, four hundred and fifty-eight metres per second by definition," I recite. I'm a geek. You know this.

"And the radius of the Earth's orbit?"

"Just under a hundred and fifty million kilometres." I frown and look up, cogs a-whirring in my head. Ed counts from the stopwatch.

"Eight minutes fifteen, eight minutes sixteen, eight minutes seventeen-"

The Sun goes out.

There is no sound, there is no descending "pyeeow" tone of power generators spinning to a halt, but suddenly the world is plunged in total darkness. All the birds stop singing. I hear a very distant honking as cars screech to a halt in the middle of the road. There are stars visible overhead. My eyes aren't adjusted to the darkness - I can't see a thing, least of all Ed, but I can hear him beside me, laughing uproariously like the lunatic genius he always was.

"Well, so much for the rumours of the Daystar," is the funniest line I can come up with on such short notice.

Five seconds later the Sun came back on again, just as Ed promised. We went back inside and performed the traditional post-experiment ritual of getting some popcorn and watching the news reports about it on TV. Ed, the forward-thinking guy he is, already has a blank videotape cued up. The press seemed to be pretty excited about this one, and personally I didn't blame them.

"Are you gonna tell them who did it?"

"Probably not," said Ed. "See, if I did, I'd get loads of credit for it, but they'd probably lock me up as well. Whereas if I leave it as a total mystery, I've got this great gag lined up for Christmas 2012..."