
I myself have dreamed up a structure intermediate between Dyson spheres
and planets.  Build a ring 93 million miles in radius -- one Earth orbit
-- around the sun.  If we have the mass of Jupiter to work with, and if
we make it a thousand miles wide, we get a thickness of about a thousand
feet for the base.

And it has advantages.  The Ringworld will be much sturdier than a Dyson
sphere.  We can spin it on its axis for gravity.  A rotation speed of 770
m/s will give us a gravity of one Earth normal.  We wouldn't even need to
roof it over.  Place walls one thousand miles high at each edge, facing the
sun.  Very little air will leak over the edges.

Lord knows the thing is roomy enough.  With three million times the surface
area of the Earth, it will be some time before anyone complains of the
crowding.
		-- Larry Niven, "Ringworld"
