The centre of an atom is its nucleus, which has shells of electrons hurtling around it. The nucleus consists of protons, which are electrically charged particles, and neutrons, which have no electrical charge at all. The nuclei of similar atoms usually contain the same numbers of electrons and protons, but sometimes the number of neutrons varies. These atoms with different numbers of neutrons are known as isotopes.
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There are many smaller particles, and more are being discovered. These very small particles are known as subatomic particles. The electron revolving around the atom, and the neutron and the proton that make up the nucleus, are all subatomic particles.
Another type of subatomic particle is the positron. It is the same as an electron but with a positive electrical charge. If a positron collides with an electron they are both destroyed and form a shower of even smaller particles. Even neutrons and protons are thought to consist of even smaller particles, called quarks. Photons, gluons and bosons are other forms of subatomic particles, and there may be as many as 100 different types altogether.
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Atoms are the smallest pieces of matter. They are the tiniest particles into which a substance can be divided without changing into something else. Atoms actually consist almost entirely of open space, in which tiny particles orbit the central particle, or nucleus. The particles travel so fast that they seem to be solid.
Atoms are so tiny that the smallest particle visible to the naked eye would contain about one million billion atoms. Despite their tiny size, atoms can be seen individually under very powerful electron microscopes.
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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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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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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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