A natural refinement to the invention of the wheel, gears were thought to have been invented by the Greeks. Philosopher and scientist, Aristotle, wrote about a rotating wheel that turned another wheel in the opposite direction in the fourth century B.C.E. By the third century B.C.E., water wheels and clocks were common on the Greek peninsula. Yet, the first specific mention of gears in Greek writings occurred around 50 C.E. by Heron of Alexandria, a mathematician and inventor. Heron is most renowned for Metrica, a three-volume compendium of observations of the mathematics and engineering of Babylonia, ancient Egypt, and the Greco-Roman world.
Charles Bolden, a former space shuttle commander and National Aeronautics and Space Administration (NASA) Administrator from 2009 to 2017, dreamed of being the first person on Mars when he first checked in for astronaut training in 1980. At the time, NASA thought that a crewed Mars mission was thirty years away. Of course, we know now that prediction was overly optimistic. Yet there have been technological advancements and a renewed interest in human exploration of the Red Planet in the past few years. How soon could a Mars mission be possible, and what technology will NASA need to make it a reality?