Does anyone think the U2 song "No Line On The Horizon" might be a tribute to Larry Niven's novel Ringworld? The novel describes an engineered, rotating ring-shaped "planet" that occupies an entire orbit around a star. The inside of the ring is populated. Looking afar (e.g. spinward, or anti-spinward) from the inside, the ring appears to curve up toward the horizon, which results in "no line on the horizon."