My Science School

 

 

 

               

Niels Bohr, a Danish physicist, was awarded the Nobel Prize in 1922 for his discovery of the structure of the atom. He went on to help develop the atomic bomb in 1943.

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               The smallest part of a substance that can exist on its own is a molecule. This consists of anything between two and several thousand atoms, which are linked together by chemical bonds. Sometimes the molecule consists of identical atoms, and it is called an element. When a group of different types of atom is connected together in this way, it forms a compound.

               The way in which the atoms become linked depends on the types of chemical bonds. This, in turn, determines the shape the molecule and its chemical properties.

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               Quantum mechanics helps us to understand how energy is used or released by atoms. Negatively charged electrons circle about the positively charged nucleus of the atom. They stay in the same orbit, until this is disturbed, and each orbit has its own level of energy. If more energy is added, when the atom is heated or when light shines on it, the electron jumps out to another orbit, absorbing the extra energy. Then when it drops back again to its original orbit, it releases this energy as heat or light. This tiny packet of energy is called a quantum. Heisenberg’s Uncertainty Principle states that it is not possible to measure exactly where a subatomic particle is and how fast it is moving, because any attempt to measure it will disturb the particle and change its characteristics.

               Atoms consist almost entirely of empty space, because almost all their mass is concentrated into the nucleus. If an atom were enlarged to the size of a football, its nucleus would still be too small for you to see it with the naked eye.

What are electrons?

               Electrons are the very tiny particles that travel around the nucleus of an atom at incredibly high speed. They carry a negative electrical charge.

               The circling electrons are arranged in different layers called shells. If there are many electrons circling around the atom and the outer shell is full, the atom will not react with other substances. If the outer shell is not full, the atom can gain or lose its electrons as it reacts chemically with other atoms around it.

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               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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               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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            The Ancient Egyptians were the first to make sundials, in 2000 BC. They were inspired by the movements of shadows as the sun advanced across the sky. The earliest known of these clocks dates from the 14th century BC. The night time charts were based on water clocks. Water clocks were designed with sound-producing bells to indicate hours.

            Around 1090, the Chinese astronomer Su Sung devised the  first mechanized water clocks. Mechanical clocks that were not powered by water slowly started appearing in the 13th century, but they were heavy. In the 15th century, portable clocks and watches were introduced. It was Salomon Coster and Jan van Call who first produced a pendulum clock.

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           A sphygmomanometer is a device used to measure blood pressure. One of the most important men in the development of the sphygmomanometer was the Austrian physician Karl Samuel Ritter Von Basch. The first clinically applicable sphygmomanometer was invented by him in 1881. Von Basch introduced the aneroid manometer, which uses a round dial that provides a pressure reading.

               An improved version was introduced by Scipione Riva-Rocci in 1896. Later, in 1901, the neurosurgeon Dr. Harvey Cushing introduced Riva-Rocci’s device in the USA, modernized it and popularized it within the medical community. In 1905, Russian physician Nikolai Korotkov discovered ‘Korotkov Sounds’ and included diastolic blood pressure measurement.

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               A barometer is an instrument that measures atmospheric pressure.

               It was during the 17th century that a series of experiments conducted by Italian scientist Evangelista Torricelli resulted in the invention of a basic barometer.

               Torricelli was the first to notice that air pressure changes, related to weather changes, indeed caused the water level to rise and fall within a 35 foot tube experiment he set up within his home. He later used mercury in it.

               The barometer utilizes the principle that as atmospheric pressure pushes down on the surface of the mercury in the cistern, the mercury in turn, pushes up with an equal pressure in the glass tube.

               It wasn’t until about the year 1670 that barometers began to be used as a weather instrument in homes since 1670.

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            A stethoscope is a dependable clinical tool used for the physical assessment and monitoring of a patient. The stethoscope was invented in 1816 by a French scientist, Rene Laennec. He placed a rolled piece of paper between the patient’s chest and his ear; he found that this could amplify the sound of the beating heart. This was readily accepted, as it did not require physical contact.

            In 1851, Irish physician Arthur Leared invented a basic binaural stethoscope. In 1852, George Philip Cammann introduced the modern binaural stethoscope for commercial production. Rappaport and Sprague designed a new stethoscope in the 1940s, which became the standard by which other stethoscopes are measured.

            In the early 1960s, an improved model was developed by David Littmann. Later, in 1999, Richard Deslauriers patented the first external noise reducing stethoscope, named DRG Puretone.

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