One day, natural gas and crude oil will really become things of the past. As others pointed out, those are resources which will run out. And besides, they are problematic for the environment. The world is already moving in the direction of renewable energy, but the future won’t belong to just one energy source. A mix of renewable energy like solar, wind, and hydro, combined with nuclear power and perhaps new technologies. That would be much better for our planet and for humanity as well, but unfortunately, the road there is not that simple, and it really depends on the country and region you live in.