Ah, but that only works for this version of the riddle. The version I know is that there are three bulbs and three switches, and you have to figure out which switch controls which bulb. Same solution as above, but with the advantage of being immune to this particular form of smart-assery.
Alternate solution with no trips upstairs: find the electrician who wired the house and tell him “I’ll give you this nice barometer if you tell me which switch controls the attic light.”
Yeah, but I’m an inveterate smartass. Thus, I have three buzzers, each with a different tone. 
“Not the third switch! Don’t throw the third switch! AAAAAAAAAAAAAaaaaaaaaaa!”
Is that story from Feynman, or am I just imagining it?
It’s a parody of an alternate solution to the puzzle of how to find the height of a building using a barometer. Have no idea who came up with this alternate solution.
Yeah, this is a standard high school physics joke. Correct answer - measure pressure at street level and on roof, use the formula you’re currently learning that details how air pressure varies with altitude. Smart ass answer - drop barometer off roof, measure time it takes to fall, use the formula you learned back in the first week of class s = 1/2 at[sup]2[/sup]. Really smartass answer - Go to the basement, find the building super, and offer him a shiny new barometer if he’ll tell you how tall the building is.
Unless of course they were behind three doors, and after you picked one your host opened one of the two remaining doors and asked if you wanted to switch.
But I thought the switches were on the walls, not the doors. 
For the record, I really like Q.E.D.'s answer.
Ah, you’re obviously not familiar with the Monty Hall Problem.
w.r.t. the OP.
I didn’t get it, I’m useless at lateral thinking puzzles, but it’s at least partly because they often need you to make similar assumptions to the dude who originally thought of the puzzle.
And yet, you still feel like kicking yourself when told the solution…
Oh, I’m all too familiar with the Monty Hall problem. I was making an (admittedly bad) pun about switching doors vs. switching lightbulbs.
As a small hijack, how well does the solution to this riddle hold up in the face of new technology? For example, I don’t know how fast compact fluorescent bulbs build up or dissapate heat. Would that make a difference in the solution? (That is, if there isn’t enough heat remaining in the bulb when you walk into the room, the solution fails.)
I thought I had a way to do it, but the chicken would eat the grain.
I have an old book at home with a version of this written by a university Physics professor (a real guy), but he presents it as a true story that happened to him. His version is very elaborate. The student comes up with a litany of possible solutions, including: walking up the stairwell and marking off “barometer units” on the wall; lowering the barometer on a rope and measuring the rope; and making a pendulum of the barometer and measuring its something-or-other at each location (Physics was too long ago for me). He does end with the “I will give you this barometer…” punchline, and the professor relents, passing the sutdent. The story goes over several pages. I doubt the story is really true, but it’s an especially well-told version.
I wondered about that. A small experiment with the CFL in my living room lamp shows that it warms up in a few minutes, and 1 minute after being shut off is still warm - not as much as an incandescent bulb, but still detectable. LED illumination may be another story, though.
Flick switch #1, go outside, see if attic light is on. If not, repeat with #2. If neither turn the light on, it’s switch #3.
If you think I’m running up to the attic and back to see if the light is on, you’re crazy.
So, I thought you’d been whooshed, but really it was me…
I’d rather run up and down the stairs twice than wait 5 to 10 minutes. It’s good exercise and I’m impatient.
That’s why, for me, the premise that I can only go upstairs once makes me implicitly rule out ‘slow’ solutions – because they’re more hassle</sour_grapes>
I have a few of those myself. I also have a receptacle in the kitchen that’s on the same circuit as an upstairs bedroom ceiling light. And there was a receptacle in the dining room that was connected to standard lamp cord which went through a hole in the floor, and was plugged into a receptacle in the basement. The previous owner was very creative.