In a wonderful article on deep cave exploration, Burkhard Bilger shows how powerful comparison can be in putting an unfamiliar topic into context. He is describing the arduous work involved in deep cave exploration. He is describing the risks of being far, far inside the cave when a heavy rain on the surface begins to flood the cave. There’s no quick way out, you see:
To climb straight back to the surface, without stopping to rig ropes and phone wire, would take them four days. It took three days to get back from the moon.
That last little detail, about coming back from the moon, is a beautiful piece of writing, and a wonderful way to remind people of how difficult it can sometimes be to travel in unexplored part of our own planet.