PARACELSUS (1493-1541)

Europe – early sixteenth century

‘Added salt to the mercury/sulfur diad, making a trinity to match the holy trinity’

picture of philippus aureolus theophrastus_paracelsus


Elaborating his writings with occult mystery, Theophrastus von Hohenheim renamed himself Paracelsus and helped to reform medicine by making it chemical.
Many of his ideas were erroneous and his writings were deliberately obscure; he insisted that the ‘doctrine of signatures’ could reveal efficacious drugs for different organs. Proclaiming that specific therapies could counter a particular disease was a radically different approach to the Aristotelian attempts to rebalance an individual’s internal humors.

Paracelsus extended the ‘fundamental qualities’ of the four Aristotelian elements by adding a third ‘hydrostatic principle’ to the diad of J’BIR IHBIN AYAM – saying the material manifestation of the ancient elements ( ‘…everything that lies in the four elements’ ) may be reduced to mercury, sulfur and salt.

The first distillate of an organic substance would be the thin, volatile ‘mercury’, which acted in favour of youth and life while next came the ‘sulfur’, acting in favour of growth and increase. Finally, the dry mass left behind was the ‘salt’. The concept of these three principles was considered a slight advance upon that of the four elements.

These are not the same things as we recognize today, nor elements in their own right; the first two were components of metals, salt was a principle common to all living things.

The Royal physicians of Elizabeth I of England and Henry IV of France assimilated and adapted Paracelsus’s ideas and although his theories lost credibility, his chemical remedies entered mainstream medicine.

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1738 – Switzerland
1859 – England

‘Gases are composed of molecules which are in constant random motion and their properties depend upon this motion’

The volume of a gas is simply the space through which molecules are free to move. Collisions of the molecules with each other and the walls of a container are perfectly elastic, resulting in no decrease in kinetic energy. The average kinetic energy of a gas increases with an increase in temperature and decreases with a decrease in temperature. The theory has been extended to provide a model for two states of matter – liquids and solids.

Bernoulli had a great advantage over DEMOCRITUS. He knew that free atoms were more than simply tiny grains flying though space; they were tiny grains flying through space and obeying NEWTON’s Laws of Motion.
Bernoulli proposed a ‘bombardment theory’, which stated that a gas consisted of tiny particles in rapid, random motion like a swarm of angry bees. He realized that in the case of such a gas visualized as a host of tiny grains in perpetual frenzied motion, the atoms hammering relentlessly on the walls of any containing vessel would produce a force by bombarding the container. The effect of each individual impact would of course be vanishingly small. The effect of billions upon billions of atoms, hammering away incessantly, however, would be to push the walls back. A gas made of atoms would exert a jittery force that we would detect as a ‘pressure’.

Heating a gas would make its particles move faster.
The pressure of a gas such as steam was easy to measure using a piston in a hollow container. This was essentially a moveable wall. To deduce how the pressure of a gas would be affected by different conditions, Bernoulli first made some simplifying assumptions. He assumed the atoms were very small compared to the gulf between them. This allowed Bernoulli to ignore any force – whether of attraction or repulsion – that existed between them, as being unlikely to be ‘long range’. (This is an ‘ideal’ or ‘perfect’ gas. The behaviour of a real gas may differ from the ideal, for example at very high pressure). With the motion of each atom unaffected by its fellows, Newton’s laws dictated that it should fly at a constant speed in a straight line. The exception was when it slammed into a piston or the walls of the container. Bernoulli assumed that in such a collision a gas atom bounced off the walls of the surface without losing any speed, in the process imparting a miniscule force to the wall.

What would happen if the volume of the gas were reduced by applying an outside force to the piston? If the gas were reduced to half its original volume, the atoms would now have to fly only half as far between collisions, in any given time they would collide with the piston twice as many times and would exert twice the pressure. Similarly, if the gas were compressed to a third of its volume, its pressure would triple. This had been observed by ROBERT BOYLE in 1660 and named Boyle’s Law.

What would happen to the pressure of gas in a closed cylinder if the gas were heated while its volume remained unchanged? Exploiting the insight that the temperature of a gas was a measure of how fast on average its atoms were flying about, that when a gas was heated, its atoms speeded up, he deduced that as the atoms would be moving faster they would collide with the piston more often and create a greater force. Consequently the pressure of the gas would rise. This was observed by the French scientist JACQUES ALEXANDRE CESARE CHARLES in 1787, and christened Charles’ law.

After 120 years MAXWELL polished Bernoulli’s ideas into a rigorous mathematical theory. In Germany, LUDWIG  BOLTZMANN championed the atomic hypothesis, but was refuted by the Austrian ERNST MACH, who was convinced that science should not concern itself with any feature of the world that could not be observed directly with the senses.


‘As the velocity of a liquid or gas increases, its pressure decreases; and when the velocity decreases, its pressure increases’

At a narrow constriction in a pipe or tube, the speed of a gas or liquid is increased, but its pressure is decreased, according to Bernoulli’s principle. This effect is named the Venturi effect (and a pipe or tube with a narrow constriction the Venturi tube) after the Italian G.B. Venturi (1746-1822) who first observed it in constrictions in water channels. An atomiser works on the same principle.


The principle is expressed as a complex equation, but it can be summed up simply as the faster the flow the lower the pressure.

An aircraft wing’s curved upper surface is longer than the lower one, which ensures that air has to travel further and so faster over the top than it does below the wing. Hence the air pressure underneath is greater than on top of the wing, causing an upward force, called lift.

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1755 – Switzerland

‘Analytical calculus – the study of infinite processes and their limits’

Swiss mathematician. His notation is even more far-reaching than that of LEIBNIZ and much of the mathematical notation that is in use to-day may be credited to Euler.

The number of theorems, equations and formulae named after him is enormous.
Euler made important discoveries in the analytic geometry of surfaces and the theory of differential equations.

Euler popularised the use of the symbols  Π (Pi);  e , for the base of the natural logarithm; and  i , for the imaginary unit.
Euler is credited with contributing the useful notations   f (x) , for the general function of  x ; and   Σ , to indicate a general sum of terms.

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1905 – Switzerland

  1. ‘the relativity principle: All laws of science are the same in all frames of reference.
  2. constancy of the speed of light: The speed of light in a vacuüm is constant and is independent of the speed of the observer’
photo portrait of Albert Einstein &copy:


The laws of physics are identical to different spectators, regardless of their position, as long as they are moving at a constant speed in relation to each other. Above all the speed of light is constant. Classical laws of mechanics seem to be obeyed in our normal lives because the speeds involved are insignificant.

Newton’s recipe for measuring the speed of a body moving through space involved simply timing it as it passed between two fixed points. This is based on the assumptions that time is flowing at the same rate for everyone – that there is such a thing as ‘absolute’ time, and that two observers would always agree on the distance between any two points in space.
The implications of this principle if the observers are moving at different speeds are bizarre and normal indicators of velocity such as distance and time become warped. Absolute space and time do not exist. The faster an object is moving the slower time moves. Objects appear to become shorter in the direction of travel. Mass increases as the speed of an object increases. Ultimately nothing may move faster than or equal to the speed of light because at that point it would have infinite mass, no length and time would stand still.

‘The energy (E) of a body equals its mass (m) times the speed of light (c) squared’

This equation shows that mass and energy are mutually convertible under certain conditions.

The mass-energy equation is a consequence of Einstein’s theory of special relativity and declares that only a small amount of atomic mass could unleash huge amounts of energy.

Two of his early papers described Brownian motion and the ‘photoelectric’ effect (employing PLANCK’s quantum theory and helping to confirm Planck’s ideas in the process).

1915 – Germany

‘Objects do not attract each other by exerting pull, but the presence of matter in space causes space to curve in such a manner that a gravitational field is set up. Gravity is the property of space itself’

From 1907 to 1915 Einstein developed his special theory into a general theory that included equating accelerating forces and gravitational forces. This implies light rays would be bent by gravitational attraction and electromagnetic radiation wavelengths would be increased under gravity. Moreover, mass and the resultant gravity, warps space and time, which would otherwise be ‘flat’, into curved paths that other masses (e.g. the moons of planets) caught within the field of the distortion follow. The predictions from special and general relativity were gradually proven by experimental evidence.

Einstein spent much of the rest of his life trying to devise a unified theory of electromagnetic, gravitational and nuclear fields.

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ABDUS SALAM (1926- 96)

1979 – Switzerland

‘Unification of the weak nuclear force and the electromagnetic force’

Photograph of Abdus Salam &copy:


Awarded the 1979 Nobel Prize for Physics along with Steven Weinberg and Sheldon Lee Glashow.

The Standard Model of quarks, electrons, neutrinos, gluons and Higgs particles.

Physicists introduced two new interactions, the strong and weak nuclear forces.
Unlike gravitation and electromagnetism these forces operate only at very short distances, distances of the order of the diameter of the nucleus or less.

Weak interactions change neutrons into protons and visa-versa in radioactive processes within stars. They are responsible for the so-called radioactive beta decay.

Strong forces hold quarks together inside protons and neutrons, as well as holding protons and neutrons together inside atomic nuclei.

The standard model of particle physics has unified electromagnetism with the weak interactions, and provides an explanation of the strong interactions. There are still huge gaps in the theories, for example there is no way of creating a unified understanding of strong and weak interactions.

Abdus Salam introduced the electroweak theory, which now sits at the core of the standard model of high-energy physics.
Energy in sunlight is produced when hydrogen fuses, or burns, into helium in a chain of nuclear reactions occurring in the Sun’s interior. In the first step of this chain reaction, weak forces enable hydrogen to transform into heavy hydrogen (deuterium).

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‘Scanning Electron Microscope’

1980 – Switzerland

SEM image of Caffeine crystals. Credit: Annie Cavanagh. Wellcome ImagesSEM image of Diatom frustule.SEM image of Moth Fly

If a needle charged with electricity is placed extremely close to the surface of a metal or semi-conductor a miniscule but measurable electric current, known as a ‘tunneling current’ will leap the gap. This current is extraordinarily sensitive to the width of the gap. The size of the tunneling current therefore reveals the distance between the needle tip and the surface.

Photograph of Gerd Binnig - worked on the scanning-tunneling electron microscope ©


Photograph of Heinrich Rohrer - worked on the scanning-tunneling electron microscope ©


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