He estimated the radius of the Earth to «be about 6,339 km (...) which gives the Earth’s circumference to be about 39,830 km which is more accurate than Eratosthenes’ calculation of about ...

This classification applies to objects over 492 feet in diameter that come within a 4.6 million mile radius of Earth. And with ... 38,000 miles per hour (17.17 kilometers per second), Asteroid ...