In space, today, we're in pre-aviation days: we're still using hot air balloons for transportation. We make them lighter than air (i.e. shoot them up in space) and let the wind (i.e gravity) to carry them places.
Imagine the most educated human 120 years ago is being told about planes heavier than air, air transportation over oceans, jet-powered planes, autopilots and fly-by-wire, not to mention people on the moon. He would say it's impossible, due to energy constraints. Today a daily JFK-NRT flight uses more energy than all the horses which lived two centuries ago would be able to produce in their lifetimes, combined (my math may be off by one order of magnitude: it's late here). Today we're this person. Educated enough to have valid arguments against it, but utterly incorrect.