Category Archives: History

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 the northern hemisphere) in Syene (modern Aswan, Egypt), the Sun was directly overhead – Syene was in fact slightly north of the tropic, though (1). Local noon is – technically when the sub-solar point is somewhere over your meridian, it’s noon for you. So, on that day, Syene is the sub-solar point of Earth (the sub-solar point on a planet is where its sun is perceived to be directly overhead). To learn more about the local noon and the subsolar point, see the article titled “How Earth Moves“.

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Ava, the bronze-age woman

A woman’s face, who buried over 3,700 years ago in Northern Scotland has been reconstructed by a team of archaeologists and forensic artists led by Maya Hoole. It was the bronze-age at that time in the area.

In 1987 the remains of an individual (a woman between 18-22 year old) buried over 3,700 years ago were discovered at Achavanich in Caithness in the north of Scotland. She was a member of a European group known as the Beaker people. She has been nicknamed ‘Ava’, an abbreviation of the place -Achavanich- she was found. The site was rescued and excavated by the Highland Regional Council Archaeology Unit. Then, the site was mostly forgotten about over the next three decades.

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Alternative Seven Wonders Of The World

The Seven Wonders of the World, describes seven great constructions known in the Hellenistic period – that’s why they are also known as the “Seven Wonders of the Ancient World”. In fact, in the Hellenistic era, each famous traveler had his own version of the list, but the best known and earliest surviving was from a poem by Greek-speaking epigrammist Antipater of Sidon, which he described in a poem composed about 140 BC:

“I have set eyes on the wall of lofty Babylon on which is a road for chariots, and the statue of Zeus by the Alpheus, and the hanging gardens, and the Colossus of the Sun, and the huge labor of the high pyramids, and the vast tomb of Mausolus; but when I saw the house of Artemis that mounted to the clouds, those other marvels lost their brilliancy, and I said, ‘Lo, apart from Olympus, the Sun never looked on aught so grand.'”

But, in fact, all seven wonders of the world existed at the same time for a period of less than 60 years. And now, only the Great Pyramid of Giza still in existence. All the others somehow gone.

If Antipater of Sidon was living in the more recent times, say 19th century, he probably would prepare a very different list. Here are the alternative seven wonders of the world that still exist today (with the images and videos):

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What if a nuclear bomb hit your city?

On August 6, 1945, during the World War II, an American Boeing B-29 Superfortress bomber named “Enola Gay” dropped the world’s first deployed atomic bomb codenamed “Little Boy” over the Japanese city of Hiroshima. The bomb exploded with 15 kilotons of TNT (63 TJ) of energy and caused horrendous destruction to the city. Approximately 66,000 people were killed as a direct result of the blast, and 69,000 were injured to varying degrees. Within four months, the number of the fatalities would reach 90,000–146,000 people due to the acute effects of the atomic bomb.

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