Ancient mariners navigated by the stars, but that method didn't work during the day or on cloudy nights, and so it was unsafe to voyage far from land.
The Chinese invented the first compass sometime between the 9th and 11th century; it was made of lodestone, a naturally-magnetized iron ore, the attractive properties of which they had been studying for centuries.
(Pictured is a model of an ancient Chinese compass from the Han Dynasty; it is a south-indicating ladle, or sinan, made of polished lodestone.)
Soon after, the technology passed to Europeans and Arabs through nautical contact.
The compass enabled mariners to navigate safely far from land, increasing sea trade and contributing to the Age of Discovery.
Compared to some of the gleaming, electronic inventions that fill our lives today, the plow doesn’t seem very exciting.
Yet the plow is probably the one invention that made all others possible.
It probably developed independently in a number of regions, and there is evidence of its use in prehistoric eras. Prior to the plow, humans were subsistence farmers or hunter/gatherers.
Their lives were devoted solely to finding enough food to survive from one season to the next.
Growing food added some stability to life, but doing it by hand was labor intensive and took a long time. The plow changed all that.
Plows made the work easier and faster.
Improvements in the plow’s design made farming so efficient that people could harvest far more food than they needed to survive.
They could trade the surplus for goods or services.
And if you could get food by trading, then you could devote your day-to-day existence to something other than growing food, such as producing the goods and services that were suddenly in demand.
The ability to trade and store materials drove the invention of written language, number systems, fortifications and militaries.
As populations gathered to engage in these activities, cities grew. It’s not a stretch to say that the plow is responsible for the creation of human civilization.
