The equator is the imaginary line that horizontally encircles the middle of Earth, stretching approximately 24,900 miles (40,000 kilometers) long. It's located halfway between the North and South poles, dividing the Northern and Southern hemispheres, with a latitude of 0 degrees.
Humans have known Earth is round for thousands of years — starting with the ancient Greeks, including Pythagoras, around 500 B.C. and confirmed by Aristotle a couple of centuries later. Shortly after this, Eratosthenes became the first person to work out the circumference of the planet.
