Asteroid mining. Mine some asteroids for iron, carbon, silicon, water. Now you have the raw materials for the biggest solar powerplant ever made. Ship the po

Asteroid mining. Mine some asteroids for iron, carbon, silicon, water. Now you have the raw materials for the biggest solar powerplant ever made. Ship the power down the space elevator and you have cheap renewable energy without the downsides of it being earthbound. Ship any excess ores down to earth for more profit. Some of those asteroids could have billions, if not trillions of tons of raw materials ready to use. It's a bit far out there as ideas go, but so was visiting the moon at one point!