From this thread on a vacuum cleaner apperantly designed by the multitalened and prophetic Freeman Dyson (who knew?):
Well, I was all set to discuss the various problems and complexities of planetary-sized artificial habitats, and it turns out to be a bigger and better Hoover. Blah. Where’s my flying car?
Anyway, the Ringworld is unstable! (I’ve always wanted to say that.) The reason shall be left for the reader as an exercise in elementry dynamics.
That is all.
Stranger
Someone read Larry Niven’s All the Myriad Ways
Or else happened to be at the Boskone where they were chanting that.
It’s so unstable, that it’s spliting in two!
Well, obviously anything with the mass of a Dyson Sphere, or even a Ringworld, will have the gravitational attraction to make an excellent vacuum cleaner!
Wait, wait, I gotta clear something up first; what’s a dyson sphre?
It’s a hypothetical construct suggested by Freeman Dyson wherein a shell would be built around a star at orbital distance so that all its energy could be harnessed.
Ah. I have heard of this idea, I just never heard what it was called.
Ah! Two threads with iden
A Dyson Sphere actually consists of several different configurations, but the most common is a shell that surrounds a sun, absorbing all energy coming from it. A shell is inherently stable because of its, well, spherical (regular) geometry. A toroid, however…not so stable.
And obviously, neither are my threads, this one having split into two. Not quite certain how that happened. 
Stranger
ticle OP’s! Nooooooo!
(http://boards.straightdope.com/sdmb/showthread.php?t=304128)
That pak? It’s killing your offspring.
It was actually James Dyson who invented it…
Dyson web site
Moderator’s Note: Duplicate threads merged.
Nah, Freeman Dyson definitely came up with the concept of the Dyson sphere.
Oh, you’re talking about the vacuum cleaner. That thing; ffffttt.
If Freeman had designed it, it would have been built by General Atomics and would have run for a hundred years off of a single charge of enriched uranium. It would also be capable of cleaning any carpet from here to Alpha Centuri in the lifespan of an average astronaut.
Don’t worry about the fallout. That’s nothing. Think of the future!
Stranger