More than 2,200 years before satellites, GPS and space missions transformed our understanding of the planet, an ancient Greek scholar achieved something extraordinary. Using nothing more than a stick, sunlight and basic geometry, Eratosthenes calculated the Earth's circumference with remarkable accuracy.
Around 240 BCE, Eratosthenes carried out an experiment that remains one of history's greatest scientific achievements. His estimate of the Earth's size came astonishingly close to the modern measurement, proving that careful observation and mathematics could answer some of humanity's biggest questions.
