My Science School

Foucault and Fizeau began working together in the late 1830s. They improved the photographic technique of the day, and used it to snap the first photo of the Sun. Working independently, the two scientists worked on measuring the speed of light.

 The son of a physicist, physician, and professor of medicine, Fizeau was born in Paris in 1819. The fact that Fizeau's father left him a fortune meant that he was free to pursue his own interests, without having to worry about making a living. Even though he initially wished to be a physician like his father, he eventually focused on scientific research, choosing to study astronomy.

Foucault was born in the same year and in the same city as Fizeau. The son of a publisher, Foucault was a rather timid boy and enjoyed limited success academically. After receiving most of his education at home, he enrolled in medical school as his mother wanted him to become a doctor. That didn't last long, however, as the mere sight of blood freaked him and he dropped out.

What Foucault lacked through formal training, he made up with his dexterity, intuitive understanding of nature, and an ability to build gadgets. Once he left medical school, he set out on his new career by working as a lab assistant.

Common love for photography

Fizeau and Foucault came together through their interest in the Daguerre photographic process that had been recently invented. Even though photography was still in its infancy and its mainstream use in astronomy was still decades away, Fizeau and Foucault decided to turn their camera towards the sun.

While they came together for this project late in the 1830s, adapting the then existing photographic process to astronomy was no easy feat. It took them years, but on April 2, 1845, they succeeded in what they set out to do - capturing the sun in considerable detail. These images are the first surviving detailed daguerreotype photographs of the surface of the sun.

Terrestrial experiment

 Fizeau's work with Foucault inspired him to attempt and calculate the speed of light, the value of which was neither known accurately, nor measured by means of a terrestrial experiment. Fizeau built an apparatus that placed a cogwheel and a mirror eight kilometres apart.

 

By sending pulses of light between them and rotating the cogwheel, Fizeau was able to observe how fast the beam of light travelled. He also observed obscured reflections when the light struck one of the cogs when the wheel was spinning very fast. By precisely measuring the times, speeds, and distances involved, Fizeau was able to calculate and arrive at the value of 3,13,300 kilometres per second for the speed of light.

Foucault replaced the cogwheel with a rotating mirror. This improved apparatus is now known as the Fizeau-Foucault Apparatus. When the mirror rotated, light was reflected at different angles, which could now be measured accurately. Foucault arrived at 2,99,796 kilometres per second for the speed of light.

Advances in technology went hand-in-hand with the work of hundreds of scientists who performed hundreds of experiments to arrive at the current speed of light's value. Defined to be 2,99,792.458 kilometres per second according to a 1983 declaration by the 17th General Congress on Weights and Measures, the speed of light is now one of the most well-established values in physics. It is measured so accurately that even the definition of metre is now a derived quantity from this. And it all started when Fizeau and Foucault decided to work together.

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Dr Robert Koch was a pivotal figure in the golden age of microbiology. It was the German bacteriologist who discovered the bacteria that causes anthrax, septicaemia, tuberculosis and cholera, and his methods enabled others to identify many more important pathogens. Thanks to his contributions to the field, he is sometimes known as the father of bacteriology, a title shared with Louis Pasteur.

Koch’s first important discovery was on anthrax, a disease that killed large numbers of livestock and some humans. Rod-shaped structures had been observed in the blood of infected animals, but the cause of the disease was still uncertain.

Koch found that the disease could be spread by the blood of infected animals, and hypothesised that it was caused by living bacteria. He developed sophisticated techniques for observing bacterial growth on microscope slides, and saw that anthrax could form spores that survived desiccation, but produced more bacteria when put back into a moist environment. This explained how contaminated soil could remain toxic for years.

Although others had earlier determined that germs cause disease – notably Pasteur and Joseph Lister – Koch was the first to link a specific bacterium, in this case bacillus anthracis, to a specific disease.

Koch learned that dyes helped to make bacteria visible and identifiable under the microscope, and published the first photographs of bacteria. He proudly announced to his parents he had taught himself to read at the age of five with the aid of the newspapers the adults read and then discarded. He even has a crater on the moon named after him. He was awarded the Nobel Prize in Medicine in 1905 for his tuberculosis findings and is considered one of the founders of microbiology.

Credit : Stanford

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Subramanyan Chandrasekhar was an Indian-born American astrophysicist who contributed to our understanding of massive stars. He shared the Nobel Prize for Physics in 1983, with William A. Fowler Born in Lahore, into a Tamil family, Chandrasekhar grew up in Madras (today's Chennai). Chandrasekhar studied physics at Presidency College, Madras, and went on to pursue graduate studies at the University of Cambridge, in England, in 1930. Here, he worked under R.H. Fowler on an improved model for the limiting mass of the degenerate star.

Chandrasekhar came up with a concept, later called the 'Chandrasekhar Limit Chandrasekhar improved upon the accuracy of the calculation in 1930 by calculating the limit for a polytrope model of a star in hydrostatic equilibrium, and comparing his limit to the earlier limit found by E. C. Stoner for a uniform density star. He showed that there is a maximum mass that a white dwarf star could reach and beyond which it would collapse or form black hole. The value of this limit was derived as 1.44 times that of solar mass. He published a series of papers related to this between 1931 and 1935. Chandrasekhar Limit was initially ignored, sometimes ridiculed, by the community of scientists because it supported the existence of back holes. But they were considered impossible at that time. It took years before the idea was accepted.

In 1937, Chandrasekhar was recruited to the University of Chicago faculty, a position he remained at until his death. He and his wife became American citizens in 1953.

Varied interest

Chandrasekhar is considered to be one of the first scientists who combined the disciplines of physics and astronomy. In fact, he was known for mastering several fields. Chandrasekhar studied stellar structure, hydrodynamics, radiative transfer, mathematical theory of black holes and colliding gravitational waves.

For 19 years, he served as editor of the Astrophysical Joumal and turned it into a world-class publication.

Chandrasekhar was instrumental in establishing the Ramanujan Institute of Mathematics in Madras in 1940s. He had strong association with many scientific institutions and young scientists back in India. Chandrasekhar died in 1995.

Legacy

Chandrasekhar was fittingly honoured by NASA when it ran a naming contest for one of the Observatories that it was planning to name after Chandrasekhar. The Chandra X-ray Observatory was launched and deployed by Space Shuttle Columbia in 1999.

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J.BS Haldane, British scientist known for his work in physiology, genetics, evolutionary biology and mathematics. J.B.S. Haldane, in full John Burdon Sanderson Haldane, (born Nov. 5, 1892, Oxford, Oxfordshire, Eng.—died Dec. 1, 1964, Bhubaneswar, India), British geneticist, biometrician, physiologist, and popularizer of science who opened new paths of research in population genetics and evolution.

Son of the noted physiologist John Scott Haldane, he began studying science as assistant to his father at the age of eight and later received formal education in the classics at Eton College and at New College, Oxford (M.A., 1914). After World War I he served as a fellow of New College and then taught at the University of Cambridge (1922–32), the University of California, Berkeley (1932), and the University of London (1933–57). Haldane’s major works include Daedalus (1924), Animal Biology (with British evolutionist Julian Huxley, 1927), The Inequality of Man (1932), The Causes of Evolution (1932), The Marxist Philosophy and the Sciences (1938), Science Advances (1947), and The Biochemistry of Genetics (1954). Selected Genetic Papers of J.B.S. Haldane, ed. by Krishna R. Dronamraju, was published in 1990.

Credit : Britannica

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Ludwig Boltzmann, in full Ludwig Eduard Boltzmann, (born February 20, 1844, Vienna, Austria—died September 5, 1906, Duino, Italy), physicist whose greatest achievement was in the development of statistical mechanics, which explains and predicts how the properties of atoms (such as mass, charge, and structure) determine. Boltzmann's general law asserts that a system will approach a state of thermodynamic equilibrium because that is the most probable state. He introduced the 'Boltzmann equation' (1877) relating the kinetic energy of a gas atom or molecule to temperature.

In the 1870s Boltzmann published a series of papers in which he showed that the second law of thermodynamics, which concerns energy exchange, could be explained by applying the laws of mechanics and the theory of probability to the motions of the atoms. In so doing, he made clear that the second law is essentially statistical and that a system approaches a state of thermodynamic equilibrium (uniform energy distribution throughout) because equilibrium is overwhelmingly the most probable state of a material system. During these investigations Boltzmann worked out the general law for the distribution of energy among the various parts of a system at a specific temperature and derived the theorem of equipartition of energy (Maxwell-Boltzmann distribution law). This law states that the average amount of energy involved in each different direction of motion of an atom is the same. He derived an equation for the change of the distribution of energy among atoms due to atomic collisions and laid the foundations of statistical mechanics.

Boltzmann was also one of the first continental scientists to recognize the importance of the electromagnetic theory proposed by James Clerk Maxwell of England. Though his work on statistical mechanics was strongly attacked and long-misunderstood, his conclusions were finally supported by the discoveries in atomic physics that began shortly before 1900 and by recognition that fluctuation phenomena, such as Brownian motion (random movement of microscopic particles suspended in a fluid), could be explained only by statistical mechanics.

Credit : Britannica

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Prof. Deepak Dhar is the first Indian to receive this top honour in the field of statistical physics. Deepak Dhar, physicist, from the Indian Institute of Science Education and Research, Pune, has been selected for the Boltzmann medal, awarded by the Commission on Statistical Physics (C3) of the International Union of Pure and Applied Physics. He becomes the first Indian to win this award, which was initiated in 1975, with Nobel laureate (1982) K.G. Wilson being the first recipient. Prof. Deepak Dhar Born on 30 October 1951 at Pratapgarh, in the north Indian state of Uttar Pradesh to Murli Dhar-Rama Gupta couple, Deepak Dhar graduated in science from the University of Allahabad in 1970 before earning a master's degree in physics from the Indian Institute of Technology, Kanpur in 1972. He shares the platform with American scientist John J. Hopfield who is known for his invention of an associative neural network, now named after him. The award consists of the gilded Boltzmann medal with the inscription of Ludwig Boltzmann, and the chosen two scientists will be presented the medals at the StatPhys28 conference to be held in Tokyo, 7-11 August, 2023. Dhar was elected as a fellow by the Indian Academy of Sciences in 1990 where he is a sitting council member.  He became an elected fellow of the Indian National Science Academy on 1995 and the National Academy of Sciences, India elected him as a fellow in 1999. Dhar received the elected fellowship of the World Academy of Sciences in 2006 and was selected for the J. C. Bose National fellowship of the Science and Engineering Research Board in 2007, with the tenure running until 2017.

Credit : Wikipedia

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