John had been genuinely surprised to learn of Sherlock's ignorance of the Earth's orbit. To be fair, the knowledge would rarely factor in to most human motives. It was just... John wondered what else Sherlock was ignorant about. Would he know what chemicals had flammable properties? Which bones would need immediate treatment when broken? How to start a fire when stranded in the woods?
John tried to stop worrying, assuring himself that whenever another one of Sherlock's gaps in knowledge surfaced, he would be there to fill it in.