My favourite Heinlein prediction is the "Shipstone" from Friday - an energy storage device that packs "more kilowatt-hours into a smaller space and a smaller ma

My favourite Heinlein prediction is the "Shipstone" from Friday - an energy storage device that packs "more kilowatt-hours into a smaller space and a smaller mass than any other engineer had ever dreamed of. To call it an "improved storage battery" (as some early accounts did) is like calling an H-bomb an "improved firecracker." In the novel, the Shipstone's eponymous inventor realised "that the problem was not a shortage of energy but lay in the transporting of energy. Energy is everywhere—in sunlight, in wind, in mountain streams, in temperature gradients of all sorts wherever found, in coal, in fossil oil, in radioactive ores, in green growing things. Especially in ocean depths and in outer space energy is free for the taking in amounts lavish beyond all human comprehension. "Those who spoke of "energy scarcity" and of "conserving energy" simply did not understand the situation. The sky was "raining soup"; what was needed was a bucket in which to carry it." I really hope this is what Elon Musk is working on next.