O'Neill Cylinders Proposed

Physicist Gerard O'Neill proposed giant rotating space habitats in the 1970s. O'Neill cylinders would be kilometers long, spinning to create artificial gravity on their inner surface. Residents would live on the inside, looking "up" across a central axis of open air, sunlight, and clouds toward the far side of the cylinder.

Jeff Bezos has championed this vision, suggesting that trillions of humans could one day live in such habitats orbiting between Earth and Mars. Building them from mined asteroid material would avoid the need to terraform entire planets.