Mood swings

I am a student of class XII. There are days when I am very depressed and feel that nothing can go right. There is no particular reason for this. I want to know how to overcome depression. I also want to know why one trends to have an unknown fear of others while in school, while travelling in a bus or walking in a public place?

Occasional depression and swings in mood are but quite common as we go through disappointments, frustrations, etc. You can get over depression if you get to the root causes for it. Once you know the cause, you can get rid of the problem effectively. You appear to be studying in Delhi. Almost every school in the city has a counsellor who can help you to overcome depression.


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When did early mathematics develop?

                The word ‘arithmetic’ is derived from the Greek word ‘arithmos’ which means numbers. Around 8000 BC, in the Middle and Near East, arithmetic began. People counted on their fingers long before the 16th century BC when the practice was first recorded by the Egyptians. Decimals based on the number 10, evolved from the habit of counting this way.

                From the 3rd millennium BC, the Sumerians used a system based on 60-which is 10 multiplied by 6, the number of constellations then known. The Babylonians inherited mathematics from the Sumerians and retained the base-60 system for astronomical calculations but they used a base-ten system for trade. The Babylonians then divided the hour into 60 minutes of 60 seconds each.

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Who first devised the numerals that we use today?

            The numerals that we use today derive, from a system used by the people of India, between the 3rd century BC and the 6th century AD. However, these numerals were described as Arabic. It reached Persia in the 9th century, then Europe, through the writings of Middle Eastern mathematicians, like Al-Khwarizmi and Al-Kindi.

            In Europe, Roman numerals were still in use until the late 1500s. Fractions were adapted to the decimal system by the 16th century mathematician, Christoff Rudolff. In the early 17th century, the Scottish mathematician John Napier brought decimal points into common use. He later became known for his invention of logarithms.

            The book Mercantile Arithmetic is the first to record the use of (+) and (-) sign. Robert Recorde devised the equal sign in the 16th century. The multiplication sign was first used by William Oughtred in England in 1631.

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Who founded the first alphabet?

               The North Semitic alphabet is the earliest fully developed alphabetic writing system. It was known as Canaanite. Canaanite was developed in Syria as early as the 11th century BC, and was spread by traders throughout the eastern Mediterranean.

               Other northern Semitic scripts that developed after 1050 BC are known as Phoenician.

               The earliest known inscriptions in the Phoenician alphabet come from Byblos. In contrast to other languages, it contained only about two dozen distinct letters, making it a script simple enough for common traders to learn.

               The Phoenician alphabet spread around the Mediterranean, particularly in Tunisia, southern parts of the Iberian Peninsula, and was spoken until the 1st century AD.

               The letters in the Ancient Greek and Hebrew alphabets were derived from the Phoenician system, though they added extra consonants and vowels. This was later adapted by the Etruscans. The Romans developed their alphabet from them. Early Latin, mainly known by inscriptions, appeared around 600 BC.

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What is the history of wrist watches?


               Until clocks small enough to be carried were invented, sundials were the only portable timepieces. Peter Henlein is today regarded as the inventor of the watch. At the beginning of the 16th century in Germany he made some of the earliest watches. One of the earliest references to what we would perhaps now call a wristwatch or at least an ‘arm watch’ was the New Year gift received by Queen Elizabeth I from Robert Dudley, the Earl of Leicester, in 1571. However, wrist watches only became popular when the German navy issued wristwatches to all its men in 1880.

               In 1926, the creation by the Rolex Company of the first waterproof and dustproof wristwatch marked a major step forward. Digital watches arrived in 1971. They were developed by the American engineers George Theiss and Willy Crabtree.

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