How Eratosthenes calculated the Earth’s circumference more than 2k years ago?

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:

No! The Earth Would NOT Look Like This Without Water

The Earth would NOT look like this without water. Please stop sharing this nonsense. Here are some numbers: the Earth has a diameter of about 12,735 kilometers (on average). The highest point on Earth is the top of Mount Everest, at 8,848 meters (29,029 feet). The deepest point on Earth is the Mariana Trench, at …