Archimedes of Syracuse

(c.?287 BC – c.?212 BC)

Archimedes of Syracuse was a Greek mathematician, physicist, engineer, inventor and astronomer. Although few details of his life are known, he is regarded as one of the leading scientists in classical antiquity. Among his advances in physics are the foundations of hydrostatics, statics and an explanation of the principle of the lever. He is credited with designing innovative machines, including siege engines and the screw pump that bears his name. Modern experiments have tested claims that Archimedes designed machines capable of lifting attacking ships out of the water and setting ships on fire using an array of mirrors.

Archimedes is generally considered to be the greatest mathematician of antiquity and one of the greatest of all time. He used the method of exhaustion to calculate the area under the arc of a parabola with the summation of an infinite series, and gave a remarkably accurate approximation of pi. He also defined the spiral bearing his name, formulae for the volumes of solids of revolution, and an ingenious system for expressing very large numbers.

The most widely known anecdote about Archimedes tells of how he invented a method for determining the volume of an object with an irregular shape. According to Vitruvius, a votive crown for a temple had been made for King Hiero II, who had supplied the pure gold to be used, and Archimedes was asked to determine whether some silver had been substituted by the dishonest goldsmith. Archimedes had to solve the problem without damaging the crown, so he could not melt it down into a regularly shaped body in order to calculate its density. While taking a bath, he noticed that the level of the water in the tub rose as he got in, and realized that this effect could be used to determine the volume of the crown. For practical purposes water is incompressible, so the submerged crown would displace an amount of water equal to its own volume. By dividing the mass of the crown by the volume of water displaced, the density of the crown could be obtained. This density would be lower than that of gold if cheaper and less dense metals had been added. Archimedes then took to the streets naked, so excited by his discovery that he had forgotten to dress, crying ‘Eureka!’ (meaning ‘I have found it!’).

Ernst Otto Beckmann

(4 July 1853 – 12 July 1923)

Ernst Otto Beckmann was a German chemist who is remembered for his invention of the Beckmann differential thermometer and for his discovery of the Beckmann rearrangement.

Ernst Otto Beckmann was born in Solingen, Germany to a family headed by Johannes Friedrich Wilhelm Beckmann, a manufacturer. The elder Beckmann’s factory produced mineral dyes, pigments, abrasives, and polishing materials, and it was there that the younger Beckmann conducted his early chemical experiments.

After a year of voluntary military service, as a pharmacist, Beckmann began studying toxicology at the TU Braunschweig with Robert Otto. Beckmann tried to apply an already-known reaction to discriminate between aldehydes and ketones. The reaction involved the use of hydroxylamine to convert benzophenone into an oxime. Treating this oxime with phosphorus pentachloride converted it into a substance already characterised by Wallach. This reaction is now known as the Beckmann rearrangement.

Daniel Bernoulli FRS

(8 February 1700 – 17 March 1782)

Daniel Bernoulli FRS (8 February 1700 – 17 March 1782) was a Swiss mathematician and physicist and was one of the many prominent mathematicians in the Bernoulli family. He is particularly remembered for his applications of mathematics to mechanics, especially fluid mechanics, and for his pioneering work in probability and statistics. His name is commemorated in the Bernoulli principle, a particular example of the conservation of energy, which describes the mathematics of the mechanism underlying the operation of two important technologies of the 20th century: the carburetor and the airplane wing.

Daniel Bernoulli was born in Groningen, in the Netherlands, into a family of distinguished mathematicians. Daniel was the son of Johann Bernoulli (one of the ‘early developers’ of calculus), and nephew of Jakob Bernoulli (who ‘was the first to discover the theory of probability’).

It was known that a moving body exchanges its kinetic energy for potential energy when it gains height. Daniel realised that in a similar way, a moving fluid exchanges its kinetic energy for pressure. A consequence of this law is that if the velocity increases then the pressure falls. This is exploited by the wing of an aeroplane which is designed to create an area above its surface where the air velocity increases. The pressure of this area is lower and so the wing is sucked upwards.

He worked with Euler on elasticity and the development of the Euler–Bernoulli beam equation. Bernoulli’s principle is of critical use in aerodynamics. Bernoulli’s equation for fluids is one of his inventions.

Robert Boyle, FRS

(25 January 1627 – 31 December 1691)

Robert Boyle, FRS, (25 January 1627 – 31 December 1691) was a natural philosopher, chemist, physicist, and inventor. Regarded today as the first modern chemist, he is best known for Boyle’s law, which describes the inversely proportional relationship between the absolute pressure and volume of a gas, providing the temperature is kept constant within a closed system. The Sceptical Chymist is seen as a cornerstone book in the field of chemistry.

Boyle was born in Lismore Castle, in County Waterford, Ireland, the son of an Earl, and received private tutoring in Latin, Greek and French before being sent to Eton College in England. He later travelled, then went on to devote his life to scientific research, taking a prominent place in the group known as the ‘Invisible College’, who devoted themselves to the growth of the ‘new philosophy’.

In 1691 Robert Boyle died of paralysis.

Anders Celsius

(27 November 1701 – 25 April 1744)

Anders Celsius was a Swedish astronomer who went on to become a professor of astronomy at Uppsala University, later going on to found the Uppsala Astronomical Observatory in 1741. In 1742 he proposed the Celsius temperature scale which takes his name. The son of an astronomy professor, Celsius was a talented mathematician from an early age and studied at Uppsala University, where his father was a teacher. In 1730 he became a professor of astronomy there.

Celsius was the first to suggest a connection between the aurora borealis and changes in the magnetic field of the Earth. At Nuremberg in 1733 he published a collection of 316 observations of the aurora borealis made by himself and others. In astronomy, Celsius began the first attempt to measure the magnitude of starlight with a tool other than the human eye.

He proposed the Celsius temperature scale in a paper to the Royal Society of Sciences in Uppsala, the oldest Swedish scientific society, founded in 1710. His thermometer was calibrated with a value of 100° for the freezing point of water and 0° for the boiling point. In 1744 he died from tuberculosis. In 1745, a year after his death, the scale was reversed by Carl Linnaeus to facilitate more practical measurement.

Jacques Alexandre César Charles

(12 November 1746 – 7 April 1823)

Jacques Alexandre César Charles was a French inventor, scientist, mathematician and balloonist.

Jacques Charles and the Robert brothers launched the world’s first hydrogen-filled balloon on 27 August 1783, from the Champ de Mars (now the site of the Eiffel Tower). It was filled with hydrogen that had been made by pouring a quarter of a tonne of sulphuric acid onto half a tonne of scrap iron. This gas was fed into the balloon via lead pipes.

On 1 December 1783, Charles undertook a solo balloon flight. This time it ascended rapidly to an altitude of about 3,000 metres, where he saw the sun again. He began suffering from aching pain in his ears so he ‘valved’ to release gas, and descended to land gently about 3 km away at Tour du Lay. Charles never flew again, but a hydrogen balloon came to be called a Charlière in his honour. Charles developed several useful inventions, including a valve to let hydrogen out of balloons and other devices, such as the hydrometer and reflecting goniometer, and improved the Gravesand heliostat and Fahrenheit’s aerometer. In addition he confirmed Benjamin Franklin’s electrical experiments.

Charles’ law (also known as the law of volumes) describes how gases expand when heated. It was first published by natural philosopher Joseph Louis Lussac in 1802, but he credited it to unpublished work by Jacques Charles, and named the law in his honour. Charles’ law states that under constant pressure, the volume of an ideal gas is proportional to its absolute temperature. The volume of a gas at constant pressure increases linearly with the absolute temperature of the gas. The formula he created was.

John Dalton FRS

(6 September 1766 – 27 July 1844)

John Dalton FRS was an English chemist, meteorologist and physicist. He is best known for his pioneering work in the development of modern atomic theory, and his research into colour blindness (sometimes referred to as Daltonism, in his honour).

In 1801, Dalton presented an important series of papers on the constitution of mixed gases; on the pressure of steam and other vapours at different temperatures, both in a vacuum and in air; on evaporation; and on the thermal expansion of gases.

He enunciated Gay-Lussac’s law or J.A.C. Charles’ law, published in 1802 by Joseph Louis Gay-Lussac. In the two or three years following the reading of these essays, Dalton published several papers on similar topics, that on the absorption of gases by water and other liquids (1803), containing his law of partial pressures now known as Dalton’s law.

The most important of all Dalton'’s investigations are those concerned with the atomic theory in chemistry, with which his name is inseparably associated.

Jean Nicolas Fortin

(1750 – 1831)

Jean Nicolas Fortin was a French maker of scientific instruments, born in Mouchy-la-Ville in Picardy. Fortin is chiefly remembered for his design of a barometer, now called a Fortin barometer, which he introduced in about 1800. In this, the mercury cistern has a glass portion through which the mercury exposed to the atmosphere can be seen, and an ivory needle which was made just to touch its mirror image in the mercury before the reading was taken. This allows for the fact that, when the mercury column in the closed tube falls, the level in the cistern rises, and the difference in height between the two cannot be accurately determined unless the height of the latter is taken into account.

Heinrich Rudolf Hertz

(22 February 1857 – 1 January 1894)

Heinrich Rudolf Hertz was the first person to conclusively prove the existence of electromagnetic waves. The scientific unit of frequency was named the hertz in his honour.

In some of his more advanced experiments, Hertz measured the velocity of electromagnetic radiation and found it to be the same as the light’s velocity. He also established beyond any doubt that light is a form of electromagnetic radiation.

His experiments expanded the field of electromagnetic transmission, and he also found that radio waves could be transmitted through different types of materials but were reflected by others, leading in the distant future to radar. His discoveries would later be more fully understood by others and be part of the new ‘wireless age’.

Robert Hooke FRS

(28 July 1635 – 3 March 1703)

Robert Hooke FRS was an English natural philosopher and polymath.

Robert Hooke was born in 1635 in Freshwater on the Isle of Wight. On his father’s death in 1648, Robert was left £40, a sum that enabled him to buy an apprenticeship. Hooke studied at Wadham College during the Protectorate, where he became one of a tightly knit group of ardent Royalists centred around John Wilkins. Here he was employed as an assistant to Thomas Willis and to Robert Boyle, for whom he built the vacuum pumps used in Boyle’s gas law experiments. He built some of the earliest Gregorian telescopes, observed the rotations of Mars and Jupiter and, based on his observations of fossils, was an early advocate of biological evolution. He investigated the phenomenon of refraction, deducing the wave theory of light, and was the first to suggest that matter expands when heated and that air is made of small particles separated by relatively large distances. He performed pioneering work in the field of surveying and map-making and was involved in the work that led to the first modern plan-form map.

In 1660, Hooke discovered the law of elasticity which bears his name and which describes the linear variation of tension with extension in an elastic spring. In 1665 Hooke published Micrographia, a book describing microscopic and telescopic observations, and some original work in biology. During this period Hooke coined the term cell for describing biological organisms.

Micrographia also contains Hooke’s ideas on combustion. His experiments led him to conclude that combustion involves a substance that is mixed with air, a statement with which modern scientists would agree, but that was not widely understood at the time. Hooke went on to conclude that respiration also involves a specific component of the air. Hooke helped Sir Christopher Wren to design safe structures.

James Prescott Joule FRS

(24 December 1818 – 11 October 1889)

James Prescott Joule FRS was an English physicist and brewer. He studied the nature of heat, and discovered its relationship to mechanical work. This led to the theory of conservation of energy, which in turn led to the development of the first law of thermodynamics. The SI derived unit of energy, the joule, is named after him.

William Thomson, 1st Baron Kelvin OM, GCVO, PC, PRS, PRSE

(26 June 1824 – 17 December 1907)

William Thomson, 1st Baron Kelvin was an Irish and British mathematical physicist and engineer who was born in Belfast. At the University of Glasgow he did important work in the mathematical analysis of electricity and formulation of the first and second laws of thermodynamics, and did much to unify the emerging discipline of physics in its modern form. He also had a career as an electric telegraph engineer and inventor, which propelled him into the public eye and ensured his wealth, fame and honour. For his work on the transatlantic telegraph project he was knighted by Queen Victoria, becoming Sir William Thomson. He had extensive maritime interests and was most noted for his work on the mariner’s compass, which had previously been limited in reliability.

Lord Kelvin is widely known for determining the correct value of absolute zero as approximately – 273.15 Celsius. Absolute temperatures are stated in units of kelvin in his honour.

Herbert McLeod

(February 1841 – October 1923)

Herbert McLeod was a British chemist, noted for the invention of the McLeod gauge and for the invention of a sunshine recorder.

McLeod was educated at Stockwell Grammar School. In 1855 he started studying chemistry in London with George Frederick Ansell. In 1856 he joined the Royal College of Chemistry, London. He worked as lecture assistant to August Wilhelm von Hofmann from 1860 on. When Hofmann received a call to the University of Berlin he joined him, but came back after a short time to the Royal College of Chemistry. McLeod became assistant to Edward Frankland. He largely stayed at the college until 1871. McLeod was appointed professor at the Royal Indian Engineering College, where he stayed till his retirement in 1901. McLeod helped Lord Salisbury, later Prime Minister, with some experiments in the 1860s.

During his time at the Royal Indian Engineering College he worked on various subjects including meteorology, physics and chemistry. In 1874 he published a paper with a new and innovative vacuum gauge, this is known as the McLeod gauge. McLeod was elected a fellow of the Royal Society in 1881 and from 1888 he was proof reading the Royal Society’s Catalogue of Scientific papers. He carried on the work with the Catalogue of the Royal Society until 1915 when his health did not allow him to continue.

He was a Fellow of the Chemical Society, and of the Royal Society, and active in the British Association for the Advancement of Science.

Sir Isaac Newton

(25 December 1642 – 20 March 1727)

Sir Isaac Newton was the English polymath who laid the foundations for much of classical mechanics used today. He showed that the motions of objects are governed by the same set of natural laws by demonstrating the consistency between Kepler’s laws of planetary motion and his own theory of gravitation.

Newton developed a theory of colour based on the observation that a prism decomposes white light into the many colours that form the visible spectrum. He also formulated an empirical law of cooling and studied the speed of sound. In mathematics, Newton shares the credit with Leibniz for the development of differential and integral calculus.

Newton was appointed Lucasian Professor of Mathematics in 1669. From 1670 to 1672, Newton lectured on optics. During this period he investigated refraction, demonstrating that a prism could decompose white light into a spectrum of colours, and that a lens and a second prism could recompose the multicoloured spectrum into white light. He also showed that the coloured light does not change its properties by separating out a coloured beam and shining it on various objects. Newton observed that colour is the result of objects interacting with already-coloured light rather than objects generating the colour themselves. This is known as Newton’s theory of colour.

From this work, he concluded that the lens of any refracting telescope would suffer from the dispersion of light into colours (chromatic aberration). As a proof of this he constructed the first known functional reflecting telescope, today known as a Newtonian telescope, which involved solving the problems of suitable mirror material and shaping.

The Principia was published on 5 July 1687. In this work, Newton stated the three universal laws of motion.

Newton’s First Law (also known as the Law of Inertia) states that an object at rest tends to stay at rest and that an object in uniform motion tends to stay in uniform motion unless acted upon by a net external force.

Newton’s Second Law states that an applied force on an object equals the rate of change of its momentum with time. The SI unit of force is the newton, named in Newton’s honour. Newton’s Third Law states that for every action there is an equal and opposite reaction. This means that any force exerted onto an object has a counterpart force that is exerted in the opposite direction back onto the first object.

A Kindle version of Newton’s ‘Principia’, written in English, can be downloaded from ‘Amazon’ for about $2.00. Also, a Kindle version of ‘The Einstein Theory of Relativity’, by Lorentz, can be downloaded from ‘Amazon’, free of charge.

Blaise Pascal

(19 June 1623 – 19 August 1662)

Blaise Pascal was a French polymath. A child prodigy educated by his father, Pascal’s earliest work was in the natural and applied sciences, where he made important contributions to the study of fluids, and clarified the concepts of pressure and vacuum.

Pascal went on to become an important mathematician, helping create two major new areas of research: he wrote a significant treatise on the subject of projective geometry at the age of 16, and later corresponded with Pierre de Fermat on probability theory, strongly influencing the development of modern economics and social science.

Marcello Stefano Pirani

(1 July 1880 – 11 January 1968)

Marcello Stefano Pirani was a German physicist known for his invention of the Pirani vacuum gauge, a vacuum gauge based on the principle of heat loss measurement. Throughout his career, he worked on advancing lighting technology and pioneered work on the physics of gas discharge.

In 1906, he made his most important invention with the development of a new type of vacuum gauge that today bears his name, the Pirani gauge. It is based on measuring the pressure dependence of heat loss from a hot wire by heat transfer to the surrounding gas and walls. In particular, it employs the change in resistivity of the heated wire (in Pirani’s original work consisting of tantalum and platinum, today, tungsten, platinum or nickel are commonly used) with temperature to determine the heat loss. Its useful measurement range lies within 10-4 mbar up to 1000 mbar.

Henri Pitot

(3 May 1695 – 27 December 1771)

Henri Pitot was a French hydraulic engineer and the inventor of the pitot tube.

He became interested in studying the flow of water at various depths and was responsible for disproving the prevailing belief that speed of water increases with depth.

In a pitot tube, the height of the fluid column is proportional to the square of the velocity. This relationship was discovered intuitively by Henri Pitot in 1732, when he was assigned the task of measuring the flow in the river Seine.

He rose to fame with the design of Aqueduc de Saint-Clément near Montpellier and the extension of Pont du Gard in Nîmes. In 1724, he became a member of the French Academy of Sciences, and in 1740 a fellow of the Royal Society. The Pitot theorem of plane geometry is named after him.

Pythagoras of Samos

(c. 570 BC – c. 495 BC)

Pythagoras of Samos was an Ionian Greek philosopher and mathematician. Pythagoras made influential contributions to philosophy in the late 6th century BC. He is best known for the Pythagorean theorem, which states that in a right-angled triangle the area of the square of the hypotenuse (the side opposite the right-angle) is equal to the sum of the areas of the squares of the other two adjacent sides – that is, a² + b² = c².

James Watt

(19 January 1736 – 25 August 1819)

James Watt was a Scottish inventor and mechanical engineer.

While working at the University of Glasgow, Watt realised that the engine designs of the time wasted energy by repeatedly cooling then re-heating the cylinder. He introduced a separate condenser, which radically improved both the power and efficiency of steam engines.

The watt is named after him – the unit of power incorporated in the International System of Units (or ‘SI’).

Thomas Young

(13 June 1773 – 10 May 1829)

Thomas Young was an English polymath. He is famous for having partly deciphered Egyptian hieroglyphics (specifically the Rosetta Stone). Young made notable scientific contributions to the fields of vision, light, solid mechanics, energy, physiology, language, musical harmony and Egyptology.

At the age of 14 Young had learned Greek and Latin and was acquainted with French, Italian, Hebrew, German, Chaldean, Syriac, Samaritan, Arabic, Persian, Turkish and Amharic. Young’s modulus relates the stress (pressure) in a body to its associated strain (change in length as a ratio of the original length). For the first time it allowed prediction of the strain in a component subject to a known stress (and vice versa). Young’s modulus depends only on the material, not its geometry, thus allowing a revolution in engineering strategies.

Young has also been called the founder of physiological optics. In 1793 he explained the mode in which the eye accommodates itself to vision at different distances as depending on changes of the curvature of the crystalline lens, being the first to describe astigmatism and hypothesized that colour perception depends on the presence in the retina of three kinds of nerve fibres.