ALCHEMY

Alchemical symbols

Understanding of the alchemists is hampered by their predilection for making their writings incomprehensible ( instant knowledge was not to be available to the uninitiated ) and the popular view that their quest was simply to isolate the Philosophers’ Stone and to use it to transform base metals into gold.
There was in fact a genuine search for mental and spiritual advance.

Using a world-view totally unlike that recognised today, the alchemists’ ideas of ‘spirit’ and ‘matter’ were intermingled – the ability to use ‘spirit’ in their experiments was the difficult part.

To transform copper to gold: – copper could be heated with sulphur to reduce it to its ‘basic form’ (a black mass which is in fact copper sulphide) – its ‘metallic form’ being ousted by the treatment. The idea of introducing the ‘form of gold’ to this mass by manipulating and mixing suitable quantities of spirit stymied alchemists for over fifteen centuries.

Whilst this transmutation of metals was the mainstream concern of alchemy, there emerged in the sixteenth century a school that brought the techniques and philosophies of alchemy to bear on the preparation of medicines, two of the main figures involved being PARACELSUS and JOHANN VAN HELMONT

THE EIGHTEENTH CENTURY

COMBUSTION and PHLOGISTON

 

Noticing that burning a candle in an upturned container, the open end of which is submerged in water, causes the water to rise into the container, Philon of Byzantium inferred correctly that some of the air in the container had been used up in the combustion. However, he proposed that this is because this portion of the air had been converted into ‘fire particles’, which were smaller than ‘air particles’.

In 1700 the German physician Georg Ernst Stahl (1660-1734) invoked ‘phlogiston’ to explain what happens when things burn. He suggested that a burning substance was losing an undetectable elementary principle, analogous to the ‘sulfur’ of J’BIR IHBIN AYAM, which he re-named ‘phlogiston’. This could explain why a log (rich in phlogiston) could seem to be heavier than its ashes (deficient in phlogiston). The air that is required for burning served to transport the phlogiston away.

The English chemist JOSEPH PRIESTLY (1733-1804), although a supporter of the phlogiston theory, ironically contributed to its downfall. He heated mercury in air to form red mercuric oxide and then applied concentrated heat to the oxide and noticed that it decomposed again to form mercury whilst giving off a strange gas in which things burnt brightly and vigorously. He concluded that this gas must be ‘phlogiston poor’.

Priestly combined this result with the work of the Scottish physician Daniel Rutherford (1749-1819), who had found that keeping a mouse in an enclosed airtight space resulted in its death (by suffocation) and that nothing could be burnt in the enclosed atmosphere; he formed the idea that the trapped air was so rich in phlogiston that it could accept no more. Rutherford regarded this as ‘phlogisticated air’ and so Priestly called his own gas ‘dephlogisticated air’.

In 1774 Priestley visited the French chemist ANTOINE LAVOISIER (1743-1794).
Using chemical reactions, Lavoisier had combined a portion of normal air with other substances.
Lavoisier repeated Priestly’s experiments with careful measurements.
Reasoning that air is made up of a combination of two gases – one that will support combustion and life, another that will not; what was important about Lavoisier’s experiments was not the observation – others had reached a similar conclusion – but the interpretation.

Lavoisier called Priestley’s ‘dephlogisticated air’, ‘oxygene’, meaning ‘acidifying principle’, believing at the time that the active principle was present in all acids (it is not). Classifying oxygen as an element, he called the remaining portion of normal air ‘phlogisticated air’, ‘azote’, meaning ‘without life’.

Oxygen is the mirror image of phlogiston. In burning and rusting (the two processes being essentially the same) a substance picks up one of the gases from the air. Oxygen is consumed, there is no expulsion of ‘phlogiston’.

Lavoisier had been left with almost pure nitrogen, which makes up about four fifths of the air we breath. We now know azote as nitrogen. Rutherford’s ‘mephitic air’ was carbon dioxide.

CALORIC

Like phlogiston, caloric was a weightless fluid, rather like elemental fire; a quality that could be transmitted from one substance to another, so that the first warmed the second up.

It was believed that all substances contained caloric and that when a kettle was being heated over a fire, the fuel gave up its caloric to the flame, which passed it into the metal, which passed it on to the water. Similarly, two pieces of wood rubbed together would give heat because abrasion was releasing caloric trapped within.

What is being transmitted is heat energy. It was the crucial distinction between the physical and the chemical nature of substances that confused the Ancients and led to their minimal elemental schemes.

ASTROLOGY

 

HEAT

 

CHRISTIAN THEOLOGY & WESTERN SCIENCE

JOHANNES GUTENBERG (1395-1468)

1450 – Mainz, Germany

Movable type

Hand-held block printing – a laborious process of carving whole pages of fixed text out of wooden slabs and reproducing copies using dies – had been used for many decades before the German inventor appeared. What Gutenberg mastered was the idea of placing individual metal letters – (his family background was in minting and metalworking, an ideal foundation for his training as an engraver and goldsmith. His skills enabled him to craft the first individual metal letter moulds) – into temporary mounts, which could then be dismantled or ‘moved’ once a page of text had been completed and reused to produce other pages.

In comparison to engraving and the single use of wooden blocks, the theoretically infinite number of different sides which could be made out of a set of metal characters, together with the speed at which a template could be created, revolutionised printing and the spread of the printed word.

GUTENBERG

Some sources credit the Chinese with inventing moveable type printing, using characters made of wood. What is notable is the quality of Gutenberg’s metal casts and press – they are almost as important as the idea of moveable type itself.

By the end of the fifteenth century tens of thousands of books and pamphlets were already in existence, giving academics the opportunity to share scientific knowledge widely and cheaply.

NEXT

JOHANNES KEPLER (1571-1630)

1609-19 – Germany

1600 – Kepler works in Prague with TYCHO BRAHE the imperial mathematician, under the patronage of Rudolph II
1601 – On Brahe’s death, Kepler inherits his position (and crucially, his astronomical notes)

KEPLER

• First Law: The planets move in elliptical orbits with the Sun at one focus

• Second Law: The straight line joining the Sun and any planet sweeps out equal areas in equal periods of time

• Third Law: The squares of orbital periods of the planets are proportional to the cube of their mean distances from the Sun

Modern measurements of the planets show that they do not precisely follow these laws; however, their development is considered a major landmark in science.

Kepler’s ardent faith in the Copernican system – ‘The Sun not only stands at the centre of the universe, but is its moving spirit’, he asserted – brought him the disfavour of religious leaders. With his realisation that the planets do not rotate in perfect circles but in fact orbit in an ellipse, he provided the mathematical explanation for planetary motion, which had eluded Copernicus and Ptolemy.

The first two laws were published in 1609 ( Astronomia Nova – New Astronomy ) and the third in 1619 ( Harmonicses Mundi – Harmonics of the World ). Their publication put an end to PTOLEMY’s cycles & epicycles. His work provided the observational and arithmetical proof to support COPERNICUS‘ theories.

His second law states that an imaginary line between the Sun and the planets sweeps out an equal area in equal periods of time.

Stating that the planets ‘sweep’ or cover equal areas in equal amounts of time regardless of which location of their orbit they are in means that, as the Sun is only one of two centres of rotation in a planet’s orbit, a planet is nearer to the Sun at some times than at others. Thus the planet must speed up when it is nearer the Sun and slow down when it is further away.

His third law finds that the period (the time for one complete orbit – a year for the Earth, for instance) of a planet squared is the same as the distance from the planet to the Sun cubed (in astronomical units). This allows distances of planets to be worked out from observing their cycles alone.

Kepler was a versatile genius who, besides discovering these three laws, compiled tables of star positions ( Tabulae Rudolphinae – 1627 ) and developed the astronomical telescope.

Kepler also studied the anatomy of the human eye and founded the science of geometrical optics ( ‘Dioptrics’ – 1611 ), proposing the ray theory of light after ALHAZEN’s discussion in Opticae Thesaurus ; he described the eye in the same terms – as a pinhole camera, with light entering through the pupil and forming an image of the outside world on the retina at the back of the eye.

His credible solution to predicting planetary motion would act as the stimulus for questions that would lead to ISAAC NEWTON‘s theory of gravity.

TIMELINE

 

THE STARS

GOTTFRIED LEIBNIZ (1646-1716)

1684 – Germany

A new method for maxima and minima, as well as tangents … and a curious type of calculation

GOTTFRIED LEIBNIZ

Newton invented calculus (fluxions) as early as 1665, but did not publish his major work until 1687. The controversy continued for years, but it is now thought that each developed calculus independently.
Terminology and notation of calculus as we know it today is due to Leibniz. He also introduced many other mathematical symbols: the decimal point, the equals sign, the colon (:) for division and ratio, and the dot for multiplication.

NEXT

 

MECHANICS

PIETER VAN MUSSCHENBROEK (1692-1761) EWALD JURGEN VON KIELEL (1700- 48)

1745 – Holland/Germany

Electricity produced by electrostatic machines can be stored in a jar

The Leyden Jar

In modern terms the Leyden jar is a capacitor or condenser.
In 1734 Stephen Gray (c.1666-1736), an English experimenter, discovered that electric charge could be conducted over distance. He also classified various substances into conductors and insulators of electricity. He suggested that metals were the best conductors and thus introduced the use of electric wire.

In 1734 Musschenbroek, a professor from Leyden in Holland discovered that electricity could be stored in a jar of water.
During the same year, von Kleist, a German scientist also discovered the same principle independently.
In later versions of what became known as the Leyden jar, water was replaced by copper foil inside and outside the jar.
The Leyden jar became a novelty and in village faires magicians used ‘electricity in a bottle’ to amaze and entertain villagers.

TIMELINE

 

ELECTRICITY

HEINRICH WILHELM MATTHIAS OLBERS (1758-1840)

1823 – Germany

Why is the sky dark at night?

This question puzzled astronomers for centuries and no, the answer is not because the Sun is on the other side of the planet.

Olbers pointed out that if there were an infinite number of stars evenly distributed in space, the night sky should be uniformly bright. He believed that the darkness of the night sky was due to the adsorption of light by interstellar space.

This is wrong.

OLBERS

What is light intensity?

Olbers’ question remained a paradox until 1929 when it was discovered that the galaxies are moving away from us and the universe is expanding. The distant galaxies are moving away so fast that the intensity of light we receive from them is diminished.
In addition, this light is shifted towards the red end of the spectrum. These two effects significantly reduce the light we receive from distant galaxies, leaving only the nearby stars, which we see as points of light in a darkened sky.

TIMELINE

 

THE STARS

Related articles

• Minute Physics (www.youtube)
• Why is the sky blue? (sciencequestionswithchris.wordpress.com)
• Why is the sky blue? (spaceplace.nasa.gov/)

JOSEF VON FRAUNHOFER (1787-1826)

1823 – Germany

The spectroscope

A significant improvement on the apparatus used by Newton. Sunlight, instead of passing through a pinhole before striking a prism, is passed through a long thin slit in a metal plate. This creates a long ribbon-like spectrum, which may be scanned from end to end with a microscope.

Cutting across the ribbon of rainbow colours are thin black lines. The lines are present even when a diffraction grating is used instead of a prism, proving that the lines are not produced by the material of a prism, but are inherent in sunlight.

An equivalent way of describing colours is as light waves of different sizes.
The wavelength of light is fantastically small, on average about a thousandth of a millimeter, with the wavelength of red light being about twice as long as that of blue light.

Fraunhofer’s black lines correspond to missing wavelengths of light.

By 1823 Fraunhofer had measured the positions of 574 spectral lines, labeling the most prominent ones with the letters of the alphabet. The lines labeled with the letters ‘H’ and ‘K’ correspond to light at a wavelength of 0.3968 thousandths of a millimeter and 0.3933 thousandths of a millimeter, respectively. The lines are present in the spectrum of light from stars, usually in different combinations.

Fraunhofer died early at the age of 39 and it was left to the German GUSTAV KIRCHOFF to make the breakthrough that explained their significance.

Astronomers today know the wavelengths of more than 25,000 ‘Fraunhofer lines’.

TIMELINE

 

THE STARS

GEORG SIMON OHM (1789-1854)

1827 – Germany

The electric current in a conductor is proportional to the potential difference

In equation form, V = IR, where V is the potential difference, I is the current and R is a constant called resistance.

Ohm’s law links voltage (potential difference) with current and resistance and the scientists VOLTA, AMPERE and OHM.

Ohm is now honoured by having the unit of electrical resistance named after him.
If we use units of V, I and R, Ohm’s law can be written in units as:

volts = ampere × ohm

GEORG OHM

TIMELINE

 

ELECTRICITY

CARL GAUSS (1777-1855)

1832 – Germany

The electrical flux through a closed surface is proportional to the sum of the electric charges within the surface

GAUSS

An electric field may be pictured by drawing lines of force. The field is stronger where these lines crowd together, weaker where they are far apart. Electrical flux is a measure of the number of electric field lines passing through an area.

Gauss’ law describes the relationship between electric charge and electric field. It is an elegant restatement of COULOMB‘s law.

  

TIMELINE

 

MATHEMATICS

 

Related articles

• Maths in a minute: Clever sums (plus.maths.org)

JULIUS ROBERT MAYER (1814- 78)

1842 – Germany

Heat is a form of energy and energy is conserved

In equation form ΔE = H − W where ΔE is the change in the internal energy of a system, H is heat energy received by the system and W is work done by the system.

The first law of thermodynamics is simply a restatement of the law of the conservation of energy: energy is neither created nor destroyed, but may be changed from one form to another.

Mayer and HELMHOLTZ, independent of JOULE and each other, came to similar conclusions at around the same time.

TIMELINE

 

HEAT