How Eratosthenes calculated the Earth’s circumference

In 240 BC, the Greek astronomer, geographer, mathematician, music theorist and librarian Eratosthenes of Cyrene (c. 276 BC – c. 195/194 BC) calculated the circumference of the Earth without even leaving Egypt. Here’s how: Eratosthenes knew that at local noon on the summer solstice (at the time of the longest day, about 21 June in […]

Top 10 driest places on Earth

Earth, the blue planet: the oceans combined with the atmosphere makes the planet look blue. So its color mainly comes from water. About 71% of the Earth’s surface is covered with water, in fact, Earth is still the only planet we know where water can exist in liquid form on the surface. Water is also […]