Category Archives: History

Why meteoroids explode before they reach Earth?

On 15 February 2013, an approximately 20-meter (66 feet) meteoroidNotes 1 entered Earth’s atmosphere over Russia, with a speed of 19.16 ± 0.15 kilometers per second (60,000–69,000 km/h or 40,000–42,900 mph). Its mass is estimated at 7,000 to 10,000 tons, one of the largest meteoroids entered Earth’s atmosphere in the recent history. Then, at 9:20 am local time (03:20 UTC), it exploded some 20 to 30 kilometers above the city of Chelyabinsk and created a gigantic fireball (known as a superbolideNotes 1) brighter than the Sun. An estimated 500 kilotons of energy was released by the explosion. For a comparison, the “Little Boy”, the atomic bomb dropped on the Japanese city of Hiroshima on 6 August 1945 exploded with an energy of approximately 15 kilotons of TNT. So, the Chelyabinsk meteor’s explosion was about 33 times stronger. The shock waves damaged several thousand buildings and injured approximately 1,500 people. No deaths were reported.
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Top 20 Countries having most number of UNESCO World Heritage Sites (2018 update)

There are total of 1031 UNESCO World Heritage Sites in the world (as of June 2016 – 802 Cultural, 197 Natural and 32 Mixed). Here are the top 20 countries having most number of UNESCO World Heritage sites.
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The Oldest Surviving Aerial Photo was Taken in 1860

On October 13, 1860, the early American photographer James Wallace Black (February 10, 1825 – January 5, 1896) climbed into a hot air balloon (named Queen of the Air) with his camera, and photographed Boston from a hot-air balloon at 1,200 feet (around 365 meters). He was not the first person to do it: two years ago, French photographer (ans also caricaturist, journalist, novelist, and “balloonist”) Gaspard-Félix Tournachon (6 April 1820 – 20 March 1910), known by the pseudonym Nadar, who photographed Victor Hugo on his death-bed in 1885, took photographs of Paris from a hot air balloon too. But the Frenchman’s photos were lost many years ago. On that day, Black took 8 plates of glass negative; 10 1/16 x 7 15/16 in, but only one good print resulted, which the photographer entitled “Boston, as the Eagle and the Wild Goose See It”. Today, it remains the oldest surviving aerial photo.
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A new star in heavens: how Crab Nebula was born

In 1054 A.D, a new, very bright star has appeared in Earth’s sky, in the constellation Taurus. Chinese, Japanese, Korean, and Arab astronomers observed the event and noted “a new bright star emerged in the heavens”. The star was so bright: for nearly three weeks, it was visible even during the day time, under the hot, shiny summer sun, and remained visible for around two years (653 days to be exact). Today, we know that that “heavenly star” was actually a supernova (SN 1054), and its remnant is what we now know as the Crab Nebula today (catalogue designations M1, NGC 1952, Taurus A).
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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 leaving Egypt. Here’s how:
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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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