Why do we know the Earth is round? Astrophysicist Neil deGrasse Tyson explains describing how ancient Greeks like Eratosthenes measured shadows in different cities, calculating Earth’s circumference with stunning accuracy, proving it’s a sphere. Ships sailing away vanish bottom-first, curving over the horizon, a sight consistent only with a rounded Earth. From space, Apollo missions snapped photos showing our blue marble, a visual knockout punch. Gravity pulls matter into spheres for objects mas

Is Earth FLAT or ROUND? Neil deGrasse Tyson, Bill Nye The Science Guy, and NASA's Michelle Thaller present the evidence to end this conspiracy theory once and for all. | Big Think