who figured out the size of the earth
Eratosthenes He is best known for being the first person to calculate the circumference of the Earth, which he did by applying a measuring system using stadia, a standard unit of measure during that time period. His calculation was remarkably accurate. He was also the first to calculate the tilt of the Earth's axis (again with remarkable accuracy). Additionally, he may have accurately calculated the distance from the Earth to the Sun and invented the leap day.[4] He created the first map of the world, incorporating parallels and meridians based on the available geographic knowledge of his era.
Earth The shape of Earth is approximately oblate spheroidal. Due to rotation, the Earth is flattened at the poles and bulging around the equator.[91] The diameter of the Earth at the equator is 43 kilometres (27 mi) larger than the pole-to-pole diameter.[92] Thus the point on the surface farthest from Earth's center of mass is the summit of the equatorial Chimborazo volcano in Ecuador.[93][94][95][96] The average diameter of the reference spheroid is 12,742 kilometres (7,918 mi). Local topography deviates from this idealized spheroid, although on a global scale these deviations are small compared to Earth's radius: The maximum deviation of only 0.17% is at the Mariana Trench (10,911 metres (35,797 ft) below local sea level), whereas Mount Everest (8,848 metres (29,029 ft) above local sea level) represents a deviation of 0.14%.[n 13]