History of Helicopters – Who Made the First Helicopter?

People for long time have dreamed of a flying machine that could rise from the ground right up. Leonardo Da Vinci around year 1500, made a drawing of giant helicopter,…

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What is Heliograph – Communicating by light

A heliograph can be seen up to 30 miles (48 kilometers) away on a clear day without a telescope. The modern heliograph is mounted on a tripod, like a camera.

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Semaphore Alphabet

Throughout history, armies and navies have sent messages across battlefields. Simple orders like “Advance” or “Retreat” could be given by bugle calls or cannon-fire. But sending reports of the battle…

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Marco Polo facts for kids

Who was Marco Polo? Marco Polo was the first European to travel to Asia and tell his story. His book, "The Travels of Marco Polo" is the most famous travel…

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Hard and soft water – How to soften hard water?

Do you live in a place where the water is "hard"? It is easy to tell if you do, because a chalky layer, or scale, will usually build up inside your…

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What are Precious Metals?

We sometimes call valuable metals, such as platinum and gold, precious metals. Platinum is the most valuable metal in the world. It is called a catalyst because it produces a…

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