Category Great Scientific Discoveries

          People were aware of shocks from eels long before they knew about electricity. Egyptian texts dating back to 2750 BC referred to these fish as the “Thundered of the Nile”.

          Ancient cultures around the Mediterranean knew that certain objects such as rods of amber, when rubbed against cat’s fur could attract light objects like feathers.

          Electricity was nothing more than an intellectual curiosity until the 1600s, when the English scientist William Gilbert wrote De Magnete on his study of electricity and magnetism. However, Benjamin Franklin is often the one credited for the discovery of electricity. Franklin came up with the concept of electricity consisting of positive and negative elements. Franklin’s idea formed the basis of many future inventions.

          Franklin’s famous kite experiment was conducted to prove his assumption that lightning was a form of electricity. He flew a kite with a metal key attached to the string during a thunderstorm. As he expected, the key conducted electricity from the storm clouds, which was transferred to the kite and gave him a shock.

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          Fullerene or buckminsterfullerene is a series of hollow carbon molecules that form either a closed cage or a cylinder. Fullerenes in the form of a closed cage are sometimes called buckyballs whereas cylindrical fullerenes are called carbon nanotubes.

          The first fullerene was discovered in 1985 by the British chemist Sir Harold W. Kroto, Richard E. Smalley and Robert F. Curl, Jr., of the United States. The trios were awarded the Nobel Prize in 1996 for their discovery.

          It is in turn named after the American architect R. Buckminster Fuller, whose geodesic dome is constructed on the same structural principles. Sumio Lijima of Japan identified the elongated cousins of buckyballs called carbon nanotubes in 1991.

         Though fullerenes had been predicted for some time, they were detected in nature and outer space only after their accidental synthesis in 1985. Until then, graphite, diamond, and amorphous carbon such as soot and charcoal were the only allotropes of carbon. The discovery of fullerenes has led to a new understanding of sheet materials and created new vistas in nano-science and nanotechnology.

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          How do we know that dinosaurs lived on Earth millions of years ago? From their fossils of course. But how do we know their age? One way to do it is through radiocarbon dating.

          The ages of objects can be determined by finding out the amount of radiocarbon in it. All living things Contain traces of carbon-14, a radio-active element of carbon. Dating an object with the help of radiocarbon is known as ‘radiocarbon dating’ and it can date objects up to 50,000 years old. Willard Libby first proposed this innovative method for dating organic material in 1946 which is done by determining the half-life of radioactive carbon.

          Carbon-14 is formed when Cosmic rays hit the atmosphere and react with atmospheric nitrogen. Carbon -14 is taken in by plants which in turn enters all living organisms through the food chain. When an animal or a plant dies, carbon-14 atoms decay at a steady rate. The amount of carbon-14 in a dead plant or animal can give us information regarding when it died. The process lies in finding the amount of carbon-14 and dating it using half-life of the element. Half-life is defined as the period of time after which half of a given sample will have decayed. The half-life of carbon-14 is about 5,500 years. This means that after 5,500 years after the death of a plant or an animal, half the carbon-14 atoms at the time of its death won’t be present. Therefore, the lesser the amount of carbon-14, the older the sample.

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          In 1932, James Chadwick became the first person to discover neutrons. Chadwick had experience working with Rutherford, who discovered protons.

          After the discovery of protons, scientists found that protons were not the only particle in the nucleus. The number of protons in the nucleus is called atomic number. It is equal to the positive charge of the atom. During atomic disintegration, scientists were baffled to find that atomic number was less than atomic mass. For example, a helium atom’s mass is four whereas its atomic number is just two.

          Because electrons have almost no mass, scientists assumed that something other than protons were adding to the mass. Chadwick kept this problem in mind even while he was engaged in other matters. He conducted many experiments to find a neutral particle with zero charge that has the same mass as a proton. Finally, Chadwick proved the existence of neutrons and determined that its mass was about 0.1 per cent more than the proton’s. In a characteristic display of modesty, he published his findings in a paper titled Possible Existence of a Neutron. Chadwick was awarded the Nobel Prize in 1935 for his discovery.

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            An isotope is any form of a chemical element that has the same number of protons in the nucleus, or the same atomic number but has a different number of neutrons in the nucleus.

            For example, three isotopes of carbon are found in nature- carbon-12, carbon-13 and carbon-14. All three have six protons, but their neutron numbers differ, being 6, 7, and 8 respectively. Isotopes may be stable or unstable. If unstable, they will be radioactive. The term isotope is a combination of the Greek word ‘isos’, meaning equal, and ‘typos’ which means place.

            Radiochemist Frederick Soddy was the first to suggest the existence of isotopes in 1913. He made this inference based on studies of radioactive decay chains. Soddy was also the first to isolate isotopes by degenerating uranium.

           The first evidence for multiple isotopes of a stable, non-radioactive element was found by J. J. Thomson in 1913. The effect of isotopes on atomic mass was discovered by Harold Urey and G. M. Murphy in 1931.

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          Nitrogen is an essential nutrient for plants. Though four-fifths of air is made up of nitrogen, plants are unable to absorb it directly. To resolve this, plants were given nitrogen-rich fertilizers. By the 1900s however, natural supplies of nitrogen such as bird droppings were in short supply.

           In 1909, German chemist Fritz Haber successfully managed to capture atmospheric nitrogen. Nitrogen was combined with hydrogen under high pressure and heat, to form ammonia which could be made into fertilizers and similar products. This process, known as the Haber process, had potential applications in industrial and agricultural sectors.

          In 1913, a research team from BASF, under the leadership of Carl Bosch developed the first industrial level application of this process, now occasionally called the Haber-Bosch process.

          In the early twenty-first century, the global demand for ammonia was over 100 million tons. The success of the Haber process lies in satisfying about 99 per cent of this demand.

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