Cars enabled people to travel and relocate more readily
Rotation.
Crop rotation is when a farmer changes the crops grown in the same field each year to ensure he gets the best harvest possible by not exhausting the soil of specific nutrients by repeatedly growing the same thing.
Sharecroppers were free people and slaves weren't. Slaves didn't "rent" a piece of someone's land and work on it. They were forced to work on land since they were owned by the land owner.
He described the elliptical orbits of the planets.
By sailing the straight across the Atlantic ocean
