VI century, giants are a problem. (I don't remember the year now, but I knew it in my dream.) They're everywhere, and threat people. Everyone fears them. A group of friends and myself are surrounded by giants, and I find refuge under a large heavy wooden bed. Once there, I discover that giants won't attack you if you're ignoring them. I ignore a giant trying to get me from the side of the bed, and all he can do is move around noisily to get my attention. I come close to him while looking the other way, and when he's on my reach I attack his eyes, immediately defeating him. The same maneuver works with a second giant, after which I can get out of under the heavy bed and teach the others: the key is to ignore them. Fast forward to the XVI century, I'm in a crowded plaza trying to measure the curvature of Earth by placing large metallic arched rods upwards. Others are placing them in other places nearby, and together the different rods should provide data for the measurement. I have no idea how it works. Giants are no longer a problem, but there is a threat of return, and we need to know the Earth's curvature to avoid it.