Science fantasy envisions things that presently are not possible according to current scientific understanding – like colonizing planets of far off stars (requiring exceeding the speed of light).
But to me techno-dreaming is more practical, involving known scientific principles that just need to be put together by engineers into a workable and economic system. Such is the Green Machine. We hear a lot about green and of course the green in Nature comes from the chlorophyll that plants use to convert sunlight, water, and soil minerals into food. The interesting thing about this process is that it also uses carbon dioxide from the air and gives back oxygen. The global warming dilemma stems from the increasing animal population which burns oxygen and gives of carbon dioxide and more seriously cuts down trees, builds huge processes that turn carbon and oxygen to carbon dioxide, and rides around in vehicles that do the same.
Well since we are so good at building things, why don’t we build a device that mimics plants – huge factories that use synthetic chlorophyll to turn carbon dioxide to oxygen while providing carbohydrates and proteins for animal food? Potentially doable - costing what I don’t know –process design and economics is always the first step. Sorry I am too old to take part – “Old men dream dreams” – or so says Prophet Joel.