1875 – USA
‘The inventor of the telephone, Bell devoted much of his life to working with the deaf’
After emigrating to Canada from Scotland in 1870, Bell met Thomas Watson, who would help Bell’s theoretical ideas become physical reality. Bell believed that if the right apparatus could be devised, sound waves from the mouth could be converted into electric current, which could then be sent down a wire relatively simply and converted into sound at the other end using a suitable device. Bell’s telephone was patented in 1876.
Bell used the money brought in from his invention to found his company AT & T and the Bell Laboratories.
Just as THOMAS EDISON improved the viability of Bell’s telephone, so Bell enhanced Edison’s phonograph.
Bell spent some time educating Helen Keller and was instrumental in founding the journal ‘Science‘.
1996 – Scotland
‘A mammal can be cloned from adult tissues’
Clones are genetically identical individuals produced from the same parent by non-sexual reproduction.
Wilmut and his team at the Roslin Institute near Edinburgh, Scotland, took the nuclei of somatic cells from the tissues of mammary glands of a mature sheep. They took eggs from another sheep, removed their nuclei, which contain DNA, and fused the somatic nuclei with the gamete cells by passing electric pulses through them. The process replaced the DNA of the egg with the genetic material from the mammary tissue. The cloned eggs were placed in a culture dish where they grew into embryos. The researchers cloned 277 eggs, of which 29 grew into embryos. These were transplanted into 13 ewes, acting as surrogate mothers. Five months later one lamb was born. The lamb, Dolly, had no father and its genes came entirely from the udder of a ewe. Dolly the cloned sheep died in 2003.
The mammal cloning experiment has been repeated successfully on other species of mammals. These experiments show that cloning humans is possible, but it has major theological, ethical, moral and social implications.
1864 – Scotland
The Scottish physicist examined Faraday’s ideas concerning the link between electricity and magnetism interpreted in terms of fields of force and saw that they were alternative expressions of the same phenomena. Maxwell took the experimental discoveries of Faraday in the field of electromagnetism and provided his unified mathematical explanation, which outlined the relationship between magnetic and electric fields. He then proved this by producing intersecting magnetic and electric waves from a straightforward oscillating electric current.
‘Four equations that express mathematically the way electric or magnetic fields behave’
In 1831 – following the demonstration by HANS CHRISTIAN OERSTED that passing an electric current through a wire produced a magnetic field around the wire, thereby causing a nearby compass needle to be deflected from north – MICHAEL FARADAY had shown that when a wire moves within the field of a magnet, it causes an electric current to flow along the wire.
This is known as electromagnetic induction.
In 1864 Maxwell published his ‘Dynamical Theory of the Electric Field’, which offered a unifying, mathematical explanation for electromagnetism.
In 1873 he published ‘Treatise on Electricity and Magnetism’.
The equations are complex, but in general terms they describe:
- a general relationship between electric field and electric charge
- a general relationship between magnetic field and magnetic poles
- how a changing magnetic field produces electric current
- how an electric current or a changing electric field produces a magnetic field
The equations predict the existence of electromagnetic waves, which travel at the speed of light and consist of electric and magnetic fields vibrating in harmony in directions at right angles to each other. The equations also show that light is related to electricity and magnetism.
Maxwell worked out that the speed of these waves would be similar to the speed of light and concluded, as Faraday had hinted, that normal visible light was a form of electromagnetic radiation. He argued that infrared and ultraviolet light were also forms of electromagnetic radiation, and predicted the existence of other types of wave – outside the ranges known at that time – which would be similarly explainable.
Verification came with the discovery of radio waves in 1888 by HEINRICH RUDOLPH HERTZ. Further confirmation of Maxwell’s theory followed with the discovery of X-rays in 1895.
Maxwell undertook important work in thermodynamics. Building on the idea proposed by JAMES JOULE, that heat is a consequence of the movement of molecules in a gas, Maxwell suggested that the speed of these particles would vary greatly due to their collisions with other molecules.
In 1855 as an undergraduate at Cambridge, Maxwell had shown that the rings of Saturn could not be either liquid or solid. Their stability meant that they were made up of many small particles interacting with one another.
In 1859 Maxwell applied this statistical reasoning to the general analysis of molecules in a gas. He produced a statistical model based on the probable distribution of molecules at any given moment, now known as the Maxwell-Boltzmann kinetic theory of gases.
He asked what sort of motion you would expect the molecules to have as they moved around inside their container, colliding with one another and the walls. A reasonably sized vessel, under normal pressure and temperature, contains billions and billions of molecules. Maxwell said the speed of any single molecule is always changing because it is colliding all the time with other molecules. Thus the meaningful quantities are molecular average speed and the distribution about the average. Considering a vessel containing several different types of gas, Maxwell realized there is a sharp peak in the plot of the number of molecules versus their speeds. That is, most of the molecules have speeds within a small range of some particular value. The average value of the speed varies from one kind of molecule to another, but the average value of the kinetic energy, one half the molecular mass times the square of the speed, (1/2 mv2), is almost exactly the same for all molecules. Temperature is also the same for all gases in a vessel in thermal equilibrium. Assuming that temperature is a measure of the average kinetic energy of the molecules, then absolute zero is absolute rest for all molecules.
The Joule-Thomson effect, in which a gas under high pressure cools its surroundings by escaping through a nozzle into a lower pressure environment, is caused by the expanding gas doing work and losing energy, thereby lowering its temperature and drawing heat from its immediate neighbourhood. By contrast, during expansion into an adjacent vacuüm, no energy is lost and temperature is unchanged.
The explanation that heat in gas is the movement of molecules dispensed with the idea of the CALORIC fluid theory of heat.
The first law of thermodynamics states that the heat in a container is the sum of all the molecular kinetic energies.
Thermal energy is another way of describing motion energy, a summing of the very small mechanical kinetic energies of a very large number of molecules; energy neither appears nor disappears.
According to BOYLE’s, CHARLES’s and GAY-LUSSAC’s laws, molecules beating against the container walls cause pressure; the higher the temperature, the faster they move and the greater the pressure. This also explains Gay-Lussac’s experiment. Removing the divider separating half a container full of gas from the other, evacuated, half allows the molecules to spread over the whole container, but their average speed does not change. The temperature remains the same because temperature is the average molecular kinetic energy, not the concentration of caloric fluid.
In 1871 Maxwell became the first Professor of Physics at the Cavendish Laboratory. He died at age 48.
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1929 – UK
‘First identification of an antibiotic – the discovery of penicillin’
The chance discovery of a mould in 1928 led to the development of a non-toxic drug, which is used to combat the bacteria that infect wounds.
Whilst Paul Erlich (1854-1915) worked in Germany to produce a ‘magic-bullet’, a compound or dye that could stick to bacteria and damage them, Alexander Fleming’s chance discovery of the antibacterial properties of the mould Penicillium notatum led him to conclude there was a chemical produced by the mould that would attack the bacterial agents of disease.
Whilst searching for a naturally occurring bacteria-killer, Fleming’s experiments were concentrated on the body’s own sources, tears, saliva and nasal mucus.
The chance discovery of the anti-bacterial properties of Penicillium notatum was not developed commercially until World War Two over a decade later.
1827 – UK
‘Tiny solid particles suspended in a fluid are in continuous random motion’
This motion is caused by constant collisions between the suspended particles and the fluid molecules.
In 1905 EINSTEIN studied Brownian motion and used it to calculate the approximate mass and size of atoms and molecules.
Brown is also remembered for discovering a small body within cells, which he named the nucleus (from the Latin for ‘little nut’). Plant cells were discovered by HOOKE.
1765 – Glasgow, Lanarkshire, UK
Watt’s steam engine was the driving force behind the industrial revolution and his development of the rotary engine in 1781 brought mechanisation to several industries such as weaving, spinning and transportation.
Although THOMAS NEWCOMEN had developed the steam engine before Watt was even born, Newcomen’s machines had been confined to the world of mining.
In 1764, when Watt was asked to repair a scale model of Newcomen’s engine he noted its huge inefficiency. The heating and cooling of the cylinder with every stroke wasted huge amounts of fuel; and wasted time in bringing the cylinder back up to steam producing temperature, which limited the frequency of strokes. He realised that the key to improved efficiency lay in condensing the steam in a separate container – thereby allowing the cylinder and piston to remain always hot. Watt continued to improve his steam engine and developed a way to make it work with a circular, rotary motion. Another of his improvements was the production of steam under pressure, thus increasing the temperature gap between source and sink and raising the efficiency in a manner later described by SADI CARNOT and elucidated by JAMES JOULE.
RICHARD ARKWRIGHT was the first to realise the engine could be used to spin cotton, and later in weaving. Flour and paper mills were other early adopters, and in 1788 steam power was used to paddle marine transportation. In the same year, Watt developed the ‘centrifugal governor’ to regulate the speed of the engine and to keep it constant.
Watt was the first to coin the term ‘horsepower’, which he used when comparing how many horses it would require to provide the same pull as one of his machines. In 1882 the British Association named the ‘watt’ unit of power in his honour.
1815 – England
‘Atoms are not the smallest thing’
After ANTOINE LAVOISIER had compiled his list of the then known elements, another 32 were added in the years following his death. Fifty kinds of fundamental building blocks for matter seemed excessive. In 1815 Prout, using AVOGADRO’s method of comparing the relative densities and weights of gases, proposed that all atoms appeared to have weights that were exact multiples of the weight of the lightest atom, hydrogen, and that the different atomic weights of elements are whole-number multiples of the atomic weight of hydrogen (Prout’s hypothesis).
He took this as proof that all atoms were actually made from hydrogen atoms and the idea was adopted as atomic theory and used for later investigations of atomic weights and the classification of the elements.
If all atoms are made from atoms of hydrogen, then it could be possible to transform an atom of one element into an atom of another.
If atoms had been assembled from other things, then they could not themselves be the smallest things in creation.
Apart from the method of weighing atoms being controversial, there are exceptions to the rule. Chlorine is 35.5 times as heavy as hydrogen.