History of Science-10.
John Dalton-(1766-1844).
Humphry Davy (1788-1829).
Jons Berzelius (1779-1848).
Joseph Louis Gay-Lussac (1778-1850).
Amadeo Avogadro (1776-1856).
William Prout (1785-1850).
Friedrich Wohler (1800-1882).
Edward Franklin (1825-1899).
Scot, Archibald Couper (1831-1892).
Friedrich August Kekule (1829-1896).
Stamslao Cannizzaro (1826-1910).
Dmitri Mendeleev (1834-1907).
Sadi Carnot (1796-1832).
Julius Robert Von Mayer (1814-1878).
James Joule (1818-1889).
William Thomson, (Lord Kelvin), (1824-1907).
Waterston (1811-1883).
Ludwig Boltzmann (1844-1906).
Willard Gibbs (1839-1903).
Robert Brown (1773-1858).
Jean Perrin (1870-1942).
During Charles Darwin’s lifetime, in the 19th century, science made the shift,
from being a gentleman’s hobby, where the abilities of an individual can have a profound impact,
to where progress depends on the work of many individuals.
From now, we will find that discoveries are made more or less simultaneously,
by different people working independently.
One aspect of this change is that it results in growing inertia, and resulting in resistance to change.
Sometimes when a brilliant individual comes up with a profound insight,
it is not accepted easily into the collective wisdom of science.
John Dalton was born in 1766.
At that time there were only around 300 people who could be classified as scientists.
By 1800 when Dalton was about to carry out his work, there were a thousand.
When he died in 1844, there were about 10000.
By 1900, there were around 100,000.
During the 19th century, the number of scientists doubled every 15years.
In comparison the population of Europe doubled from 100 million to 200 million,
between 1750 and 1850.
Humphry Davy was born in 1788, in Cornwall.
At that time Cornwall was a separate country from England.
The financial circumstances of the family was very difficult.
At the age of 9, Davy went to live with his mother’s adoptive father, John Tonkin, who was a surgeon.
Davy’s father died in 1794, leaving nothing but debt.
Tomkin advised Davy to become an apprentice of the local , apothecary,
with the ultimate ambition of studying medicine.
He also learnt French, which would prove to be invaluable to him.
While he was an apprentice he embarked on a program of self education.
In 1797, at the age of 18, he read Lavoisier’s Traite Elementaire, in the original French.
He became fascinated with chemistry.
During this time, Davy’s widowed mother took in a lodger, who was a young man suffering from TB.
He happened to be Gregory Watt, the son of James Watt, and studied chemistry.
Davy developed a friendship with him, and shared his ideas on chemistry, till Watt died at the age of 27.
Davy wrote a paper on heat and light, which he sent to Dr Thomas Beddoes.
Beddoes had studied under Joseph Black.
Davy got a job as an assistant to Beddoes, at the age of 19.
Beddoes was investigating the potential of different gases in medicine.
Davy experimented with nitrous oxide.
He inhaled it, and discovered that it had intoxicating properties.
It was soon given the name ‘Laughing gas’, and became a sensation with the pleasure seeking classes.
When he had a problem with his wisdom teeth, he discovered that the gas dulled the sensation of pain.
He wrote that it could be used in surgical operations.
But the suggestion was not followed up.
Later an American dentist Horace Wells, pioneered the use of laughing gas, in 1844,
when extracting teeth.
Davy experimented by inhaling different gases.
He had a near fatal result, when he tried to inhale a mixture of carbon monoxide and hydrogen.
Carbon monoxide is extremely poisonous.
It rapidly but painlessly induces deep sleep, which leads to death.
Fortunately Davy survived the experiment.
After studying nitrous oxide for 10 months, he published a book on it, in 1800.
Davy now started developing an interest in electricity, after the discovery of the galvanic pile by Volta.
At this time Benjamin Thomas was trying to establish the Royal institution in London.
He invited Davy to become an assistant lecturer in chemistry,
and director of the laboratory at the Royal institute, with a salary of 100 guineas per annum, in 1801.
He was a brilliant success with his lectures, which was thoroughly prepared.
His good looks and Charisma, had fashionable young ladies flocking to his lectures,
regardless of its content.
He became the professor of chemistry in 1802.
Davy was only 23 years old and had no formal college education.
He was one of the last of the great amateur scientists.
He gave a famous series of lectures, on the relevance of chemistry to agriculture.
He was awarded an honorary degree of Doctor of Laws, by Trinity college.
He listened to a lecture by John Dalton, but he was reluctant to accept Dalton’s atomic model.
Davy used electrical currents passed through potash and soda,
and isolated two previously unknown metals, which he named as potassium and sodium.
In 1810, he isolated, and named chlorine, which he proved was an element.
He established that the key component of all acids, is hydrogen and not oxygen.
He was knighted in 1812.
3 days later, he married a wealthy widow.
He appointed Michael Faraday, his eventual successor, as an assistant at the Royal Institute.
He designed the miners safety lamp, which bears his name.
He was elected as president of the Royal Society.
All the fame made him a snob.
He was the only fellow to oppose the election of Faraday to the Royal Society.
He died in 1829 at the age of 51.
John Dalton was born in 1766.
His father was a weaver.
They lived in a two room cottage, one room for working, and one for living.
He went to a Quaker school, which allowed him to develop his interest in mathematics.
At the age of 12, Dalton had to work in a farm, to contribute to the family income.
In 1785, he along with his brother managed to school, for Quakers.
He gradually developed an interest in science.
He set an answered questions in popular magazines.
He made daily meteorological observations from 1787 till he died.
He had an ambition to become a lawyer or a doctor.
His friends advised him, that there was no hope to obtaining funds to fulfil the ambition.
He started giving public lectures for a small fee.
In 1793, he became a teacher of mathematics and natural philosophy, in Manchester.
Manchester was a boom town, with the cotton industry moving out of the cottages,
and into factories.
In 1799, he became a private tutor, and earned a decent living
Dalton lived in Manchester for the rest of his life.
He was colour blind.
At that time, this condition was not recognised.
He and his brother could not distinguish between colours like blue and pink.
In 1794, he read the paper to the Manchester philosophical society, about this condition.
This became known as Daltonism.
His interest in meteorology led him to think about the nature of mixture of gases.
He thought that gas was made of particles, separated from one another by springs.
He studied the relationship between the volumes of different gases,
under various conditions of temperature and pressure.
In 1801, he came up with a law of partial pressures,
which says that the total pressure exerted by a mixture of gases is the sum of pressures each gas,
would exert on its own, under the same conditions.
In 1800 he became convinced that each element had a different kind of atom,
unique to that element.
The key distinguishing feature, which made one element different from another,
was the weight of its atoms.
Elementary atoms could neither be created or destroyed.
Elementary atoms could combine with one another to form molecules.
The biggest flaw in Dalton’s model, is that he did not realise that the elements,
such as hydrogen are composed of molecules, like H2 and not H.
Due to this he thought that water was HO, and not H2O.
He presented his ideas to the Royal Institute in 1804.
He published a book in 1808, ’System of Chemical Philosophy’,
which included a list of estimated atomic weights.
Many people found it hard to accept the idea of atoms.
It took almost half a century, for the Daltonian atom to become a feature of chemistry.
It took a hundred years to establish a definitive proof of the existence of atoms.
Dalton was heaped with honours during his long life.
He became a fellow of the Royal Society in 1822.
He died in 1844.
Jons Berzelius was born in Sweden in 1779.
His father died when he was four years old.
His mother married a pastor.
When his mother died in 1788, he lived with his uncle.
In 1796, he began to study medicine.
He had to interrupt his studies to work to pay his fees.
He graduated with an MD in 1802.
He moved to Stockholm, where he worked as an assistant to the professor of medicine,
at the college of medicine in Stockholm.
The professor died in 1807, Berzelius was appointed to replace him.
He soon gave up medicine and concentrated on chemistry.
Berzelius was a more meticulous experimenter than Davy.
He was one of the first to formulate the idea that compounds or composed of electrically positive,
and electrically negative parts.
He was a early enthusiast for Dalton’s atomic theory.
He carried out a series of experiments to measure the proportions,
in which different elements combine with each other.
By 1816, he had studied 2000 compounds.
He produced a reasonable accurate table of atomic weights, of all 40 elements known at that time.
He was the inventor for the modern alphabetical system of nomenclature for the elements.
Berzelius and his colleagues isolated and identified several new elements,
including selenium, thorium, lithium, and vanadium.
Around this time, chemists were beginning to appreciate that elements could be grouped in families,
with similar chemical properties.
Berzelius gave the name Halogens, which meant salt formers, to the group,
which included chlorine, bromine, and iodine.
He also coined the terms organic chemistry, catalysis, and protein.
His book, the text book of chemistry, published in 1803, was highly influential.
He was made a baron by the king of Sweden in 1835.
He died in 1848.
Joseph Louis Gay-Lussac published in 1809, that gases combine in simple proportions by volume,
and the volume of the products is related in a simple way to the volumes of the reacting gases.
For example, two volumes of hydrogen, combine with one volume of oxygen,
to produce two volumes of water vapour.
In 1811, Italian, Amadeo Avogadro published his hypothesis, that at a given temperature,
the same volume of gas, has the same number of molecules.
This explained Gay-Lussac discovery.
It lead to the realisation that oxygen and other elements could exist,
in polyatomic molecular form, like O2.
This was a crucial step forward.
When hydrogen and oxygen combine, each oxygen molecules, provides one atom,
to each pair of hydrogen molecules, resulting in the same number of molecules,
as there were in the original volume of hydrogen.
In modern notion 2H2 + O2 = 2H2O.
Avogadro’s ideas fell on stony ground at that time.
Progress was held up for decades, handicapped by the lack of experiments,
which could test the hypothesis.
In 1815, British chemist William Prout, suggested the atomic weights of all elements,
were the exact multiple of the atomic weight of hydrogen.
It suggested that heavier elements might be built from hydrogen.
Experiment showed that the relationship did not hold exactly.
This was because Isotopes were not discovered at that time.
Experimenters were becoming aware that all materials fall into two varieties of chemical substances.
Some like water or salt, change their character when heated, but when cooled,
revert back to original state.
Others like sugar or wood are completely altered by the action of heat, as they get burnt.
They do not revert back to their original state when cooling.
Berzelius formalised the distinction between them, and named them inorganic and organic chemicals.
Chemists realised that most of organic chemicals are more complex compounds.
However they thought that a ‘life force’ made chemistry operate differently in living things.
The implication was that organic substances could be made only by living systems.
It came as a dramatic surprise, when in 1828, German chemist Friedrich Wohler,
accidentally discovered that urea could be made by heating ammonium cyanate.
Ammonium cyanate was considered as inorganic.
By the end of the 19th century it became clear, that there was no mysterious life force,
in organic chemistry.
The definition of organic changed.
1. Organic compounds are mostly complex.
2. All organic compounds contain carbon.
Carbon atoms are able to combine in many interesting ways, with many other atoms of other elements,
and other carbon atoms.
Now ammonium cyanate, is considered as organic, since it has carbon.
Today organic chemistry is about carbon and its compounds.
Life is seen as a product of carbon chemistry.
It obeys the same chemical rules that operate throughout the world of atoms and molecules.
Together with Darwin’s and Wallace’s ideas about evolution, this produced a major nineteen century,
view of the place of humankind.
Natural selection tells us clearly, that we are part of the animal kingdom.
Chemistry tells us that animals and plants, are part of the physical world,
and there is no special ‘life force’.
In 1852, the english chemist Edward Franklin, gave the first reasonably clear analysis of valency.
Valency was the ability of a particular element to combine with other atoms.
In 1858, the Scot, Archibald Couper introduced the idea of bonds into chemistry.
Hydrogen has a valency of 1, meaning it can form 1 bond.
Oxygen has a valency of 2, meaning it can form 2 bonds.
Each of the two bonds combine with hydrogen to form H-O-H, or H2O, which is water.
Nitrogen has a valency of 3, and can produce ammonia or NH3.
Carbon has a valency of 4, which can combine with 4 other atoms.
This property lies at the heart of carbon chemistry.
Couper suggested that organic chemicals might consists of a chain of carbon atoms,
attached to other elements, with the spare bonds.
German chemist Friedrich August Kekule independently discovered this concept.
He also had the inspired insight that carbon atoms could linkup in rings.
The most common was a ring of 6 carbon atoms, forming a hexagon.
The spare bonds combined with other elements.
In the 1850’s the time was ripe to rediscover Avogadro’s work.
Stamslao Cannizzaro was born in Sicily in 1826.
He fought in the unsuccessful rebellion of the Bourbon regime, of the king of Naples.
When the uprising failed, Cannizzaro was sentenced to death in absence.
He went into exile in Paris, where he worked with Michel Chevreul, Professor of chemistry.
In 1851, he returned to Italy, where he became a professor of chemistry in Genoa.
In Genoa he came across Avodagro’s hypothesis, and compared it with the progress,
made in chemistry, since 1811.
In 1858, Cannizzaro published a paper, drawing the distinction between atoms and molecules.
He explained how the behaviour of gases, could be used to calculate the atomic and molecular weights,
relative to one atom of hydrogen.
He drew up a table of atomic and molecular weights.
This was a key influence in understanding of the periodic table of elements.
In 1871, he founded the Italian Institute of Chemistry.
He became a senator in parliament, and later Vice President of the senate.
He died in 1910.
The story of the invention of the periodic table, highlights when the time is right,
the same scientific discovery, could be made by multiple people independently.
It also illustrates the reluctance of the old guard to accept new ideas.
In the 1860’s both the English chemist John Newlands, and French mineralogist,
Alexandre Beguyer de Chancourtois, independently realised the principles of the periodic table.
That is if the elements are arranged in order of their atomic weight,
there is a repeating pattern at regular intervals.
Elements with atomic weights, that are multiple of 8 times, the atomic weight of hydrogen,
has similar properties.
The idea was rejected by their peers, saying that it made no sense.
The German chemist Lothar Meyer also came up with the same idea.
He prepared a complete version of the periodic table, but did not publish it till 1870.
By that time Mendeleev had independently propounded his version of the periodic table.
Mendeleev had gone one step further and predicted the need for new elements,
to plug the gaps, in the periodic table.
Dmitri Mendeleev was born in 1834, in Siberia, the youngest of 14 children.
His father went blind when he was a child, and he was largely supported by his mother Marya.
Marya set up a glass works to provide income for the family.
When the older children, were more or less independent, Marya decided that the youngest child,
should have the best education possible.
Due to financial constraints Mendeleev could not enrol in the university.
He enrolled as a student teacher in 1850, at the pedagogical institute,
where his father has qualified.
His mother died 10 weeks later.
Mendeleev was determined, and went on to take a master’s degree in chemistry,
at the university of Petersburg, in 1856.
He met Cannizzaro in a conference in 1860.
He completed his PhD in 1865, and went on to become a professor of chemistry,
at the university of same Petersburg.
He was forced to retire at the age of 57, in 1891 for taking the side of the students,
in a protest movement.
He went on to become the controller of the Bureau of weights and measures.
In 1906, he was nominated for the Nobel prize, but lost by one vote to Henri Moissan,
who isolated fluorine.
He died in 1907, before the Nobel committee met again.
Mendeleev made his name by writing the text book, principles of chemistry,
which was published in 2 volumes in 1868-1870.
In 1869, he published a classic paper, outlining the relationship between,
the chemical properties of the elements, and their atomic weights.
The great thing about Mendeleev’s work, was that he had the audacity to rearrange,
the order of the elements, to fit the pattern he had discovered, and to leave gaps in the periodic table,
for elements which had not yet been discovered.
He came with a arrangement in a grid, with elements in rows of 8, one under another,
so that elements with similar chemical properties lay underneath one another, in the columns of the table.
Mendeleev’s bold leap of faith was justified in the 20th century,
when it was discovered that the chemical properties of elements depends on the number of protons,
or atomic number of the element.
Atomic weights depend on the total number of protons plus neutrons.
The modern version of the periodic table ranks the elements in order of increasing atomic number.
By 1871, he had redefined the periodic table to leave gaps in the table,
and incorporate all the 63 elements known at that time.
Over the next 15 years, the 3 elements needed to plug the gaps in the table,
was discovered with the properties predicted by Mendeleev.
They were gallium, scandium and germanium.
From a mass of data, Mendeleev found a pattern, which led him to make a prediction,
that could be tested by experiment.
When the experiment confirmed his prediction, his hypothesis gained strength.
At a time, when atomic theory was not universally accepted, chemists were arriving at the evidence,
that supported the atomic hypothesis.
Physicists followed a different path, which ultimately led to incontrovertible proof, that atoms exists.
The unifying theme in this line of 19th century physics, was the study of heat and motion,
which became known as thermodynamics.
Thermodynamics both grew out of the industrial revolution, (example the steam engine),
and fed back into the industrial revolution, a scientific understanding of it.
This helped to design and build more efficient machines.
By mid 1860’s the basic laws and principles of thermodynamics had been worked out.
It took another 40 years for the implications of one small part of this work,
to be used as a definitive proof of the reality of atoms.
The key conceptual developments that led to the understanding of thermodynamics,
was the concept of energy.
It was realised that energy can be converted from one form to another,
but cannot be created or destroyed.
Work was understood as a form of energy.
The beginning of the science of thermodynamics can be traced to the French, Sadi Carnot,
in 1824, who analysed the efficiency of engines, in converting heat into work.
He showed that work is done as heat passes from a higher temperature to a lower temperature.
It implied a early form of the second law of thermodynamics, wherein heat always flows,
from a hotter object to a colder object.
He also suggested the possibility of internal combustion engine.
He unfortunately died of cholera at the age of 36.
Most of his manuscripts with his ideas were burnt, because of the nature of the disease.
He was the first to clearly appreciate that heat and work are interchangeable.
He worked out how much work, a given amount of heat can do.
Carnot’s work inspired scientists like William Thomson and Rudolf Clausius.
The German physician Julius Robert Von Mayer, published a correct determination,
of the mechanical equivalent of heat.
He studied human beings, not steam engines.
Mayer was working as the ship’s doctor of a Dutch vessel that visited East Indies, in 1840.
At that time it was believed that draining away a little blood would help to cope with the heat.
He was aware of Lavoisier’s work, that showed that warm blooded animals, are kept warm,
by the slow combustion of food, which acts as the fuel, with oxygen in the body.
He knew that bright red blood, rich in oxygen is carried around the body,
from the lungs in the arteries.
Dark purple blood, deficient in oxygen was carried back to the lungs by veins.
When he opened the vein of a sailor in Java, he was astonished to find that,
the blood was brightly coloured.
This was true for the rest of the crew, including himself.
Mayer realised that the venous blood was rich in oxygen, because in the heat of the tropics,
the body has to burn less fuel, and consume less oxygen to keep warm.
He realised that all forms of heat and energy are interchangeable.
Any type of heat, like the heat of muscular exertion, the heat of the sun, or the heat of burning coal,
could never be created, but only changed from one form to another.
Mayer, along with his medical work developed an interest in physics.
In 1842 he published his ideas about heat and energy.
Since he was a doctor, the physics scientists ignored him.
He became depressed, attempted suicide, and was confined to mental institutions in the 1850’s.
His work was rediscovered around 1858.
Mayer recovered his health, and was awarded the Copley medal, of the Royal Society in 1871.
He died in 1878.
Apart from Carnot, whose work was nipped in the bud, the first physicist who understood energy,
was James Joule.
James Joule was born in 1818, near Manchester, was the son of a wealthy brewer.
As a teenager he spent some time in the brewery.
His exposure to machinery, might have fired his interest in heat.
Joule was educated privately.
In 1834, his father sent him to study chemistry with John Dalton.
Dalton was by then 68 years old, and in failing health, but still giving private lessons.
They did not learn much from him, because Dalton insisted on teaching them Euclid for 2 years.
Dalton stopped teaching in 1837, because of illness.
Joule remained friendly with Dalton, till Dalton’s death in 1844.
In 1838, Joule converted one room in his family house to a laboratory, where he worked independently.
He was an active member of the Manchester literary and philosophical society.
He was in touch with what was going on in the scientific world.
Joule’s early work was with magnetism, where he unsuccessfully tried to invent an electric motor,
which would be more powerful and efficient than a steam engine.
In 1841, he produced a paper on the relationship between electricity and heat.
In 1842, at the age of 23, he presented his ideas to the British association, known as BA
for the advancement of science.
In 1847, he gave lectures which set out the law of conservation of energy.
He presented his ideas to the BA in 1847.
William Thomson who was 22 years old was in the audience, realised the importance of the idea.
Thomson became a friend and collaborator of Joule.
They worked on the way in which gases cool, when they expand.
This is known as the Joule-Thomson effect, the principle on which the refrigerator operates.
In 1848, he estimated the average speed with which the molecules of gas move.
For hydrogen this worked out to be about 6225 feet per second.
For oxygen which was 16 times heavier, it was around 1556 feet per second.
His work on law of conservation of energy was widely accepted.
In 1850, he was elected a fellow of the Royal Society.
William Thomson was the son of the Prof. of mathematics, in the university of Belfast.
He was born in 1824.
His mother died when he was 6 years old.
He was educated at home, by his father.
He enrolled at the university of Glasgow in 1834 at the age of 10.
He moved to Cambridge and graduated in 1845.
He published many papers in the Cambridge journal, and won many prizes.
His father helped him become the professor of natural philosophy in Glasgow, in 1856.
He remained as professor till he retired at the age of 75, in 1899.
He also enrolled as a research student in the university,
making him possibly the youngest and oldest student at the university of Glasgow.
He died in 1907, and was buried next to Issac Newton in Westminster Abbey.
Thomson was responsible for the success of the first working transatlantic cable.
He made a fortune from his various patents.
It was the success of the transatlantic cable, that led to his knighting in 1866.
He was made Baron Kelvin of Largs in 1892.
Thomson is often referred to in scientific circles as Lord Kelvin, or just Kelvin.
This was partly to differentiate him from physicists J.J. Thomson.
They absolute or thermodynamic scale of temperature is called Kelvin scale in his honour.
He worked in the areas of electricity and magnetism.
Thomson’s most important work was in establishing thermodynamics as a scientific discipline.
Continuing Carnot’s work, Thomson established the Kelvin’s scale of temperature in 1848.
This is based on the idea that heat is equivalent to work.
A certain change in temperature corresponds to a certain amount of work.
The Kelvin’s scale implies that there is a minimum temperature of minus 273 degree centigrade,
which is written as 0 degrees kelvin.
At 0 degree kelvin no more work can be done, because no heat can be extracted from the system.
Around this time Carnot’s ideas were being refined and developed by Rudolf Clausius in Germany.
Clausius and Thomson more or less independently arrived at the key principles of thermodynamics.
The first law of thermodynamics, simply says that heat is work.
The second law of thermodynamics, is possibly the most important and fundamental idea,
in the whole of science.
It says that, of its own volition, heat cannot move from a colder object to a hotter object.
In a larger universal perspective, it says everything wears out including the universe itself.
The amount of disorder in the universe, which can be measured by entropy, always increases overall.
The amount of order may increase in local regions, like in the Earth, may increase.
The Earth receives a flow of energy from the sun.
It is the law of nature that the decrease in entropy, produced by life on Earth,
is smaller than the increase in entropy associated with the processes that keep the sun shining.
This cannot go on forever.
This was the first real scientific recognition that the Earth and the universe had a definite beginning.
Thomson worked out the age of the sun, by calculating how long it could generate heat,
slowly contracting under its own weight, gradually converting gravitational energy into heat.
The answer was a few tens of million of years.
This was much less than the time scale required by geologists and the evolutionists in the 1850’s.
The resolution of the puzzle came with the discovery of radioactivity, and then Einstein’s work,
showing that matter is a form of energy.
This included the famous equation E = mc squared.
This came much later.
The conflict between the timescales of geology and evolution, and the time scales of physics,
was very real in the second half of the nineteen century.
This work brought Thomson, into conflict with Hermann von Helmholtz,
who arrived at similar conclusions independently.
This was in spite of the unfortunate Mayor and Waterston who got their first.
Waterston was born in 1811 in Edinburgh.
He was a civil engineer who went to India in 1839, to teach the cadets of the East India Company.
He saved enough to retire early in 1857, and returned to Edinburgh,
to research thermodynamics and other areas of physics.
He had been long working in science in his spare time.
In 1845, he wrote a paper describing the way in which energy is distributed among,
atoms and molecules in a gas.
Molecules had a range of speech distributed in accordance with the statistical rules,
around the mean speed.
In 1845, he sent the paper to the Royal Society.
The referees didn’t understand it, and rejected the paper, and also lost it.
Waterston did not keep a copy of the essentially right paper, and never reproduced it.
With none of his work gaining recognition, Waterston became depressed and ill.
In 1883, he walked out of his house, and never came back.
Waterston missing manuscript was discovered in the vaults of the Royal Society, and published in 1892.
By 1892, the kinetic theory of gases, and the ideas of statistical mechanics had been long established.
James Clerk Maxwell and Ludwig Boltzmann were the key players in establishing these ideas.
In 1859, Maxwell presented a paper to the British Association which outlined independently,
most of the material in Waterston’s lost paper.
He showed how the speeds of the particle in a gas were distributed around the mean speed.
He calculated that in air, each molecule experiences more than 8 billion collisions per second.
This gives the illusion that a gas is a smooth continuous fluid,
when its really made up of a large number of tiny particles in constant motion.
More significantly it was this work that led to a full understanding,
of the relationship between heat and motion.
The temperature of an object is a measure of the mean speed,
with which the molecules of the object, are moving.
This meant the abandonment of the earlier concept of caloric.
Maxwell developed this ideas further and explained properties like viscosity of gases.
He also explained why gases cool when they expand.
When gases expands the particles slow down, making the gas cooler.
Maxwell’s ideas were refined and improved by the Austrian Boltzmann.
Maxwell in turn took some of Boltzmann’s ideas and improved the kinetic theory.
The kinetic energies of the molecules in a gas around their mean,
is now known as the Maxwell-Boltzmann’s distribution.
Boltzmann made many other important contributions to science.
His greatest work was in the field of statistical mechanics.
The overall properties of matter, including the second law of thermodynamics,
are derived in terms of the constituent molecules, obeying simple laws of physics,
and the blind working of probability.
Statistical mechanics was brought to full flowering by the work of the American Willard Gibbs.
Gibbs was possibly the first American to make a significant contribution to science.
These ideas were criticised by anti atomic scientists like Wilhelm Ostwald,
who insisted that atoms were a hypothetical concept.
In 1898, Boltzmann published his paper with a detailed calculation of his theory of gases.
He became depressed because he thought his ideas would never receive the recognition it deserved.
He attempted suicide in 1900.
He recovered enough to give a series of lectures in the US.
The recovery did not last, and he hanged himself in 1906.
Albert Einstein was a brilliant young scientist, who was obsessed with idea of proving that atoms are real.
Einstein graduated from the Swiss Federal Institute of Technology, in Zurich, in 1900.
Though he did well in his final examinations, his attitude was not liked by his professors.
One of them described Einstein as a lazy dog, who did not bother about mathematics.
He was unable to get a job as one of the assistants to the professors.
They also did not give him a decent reference letter.
Einstein did a variety of part-time jobs before becoming a patent officer in 1902.
He spent most of his time, including his office time, working on scientific problems,
and published several papers between 1900 and 1905.
In 1905, he wrote a paper which established the reality of atoms and molecules.
This paper was used to get his PhD.
Scientists who accepted the idea of atoms, were already trying to estimate the size of atoms.
In 1816 Thomas Young estimated the size of water molecules, by studying the surface tension.
His estimate was 5000 to 25000 millionth of a centimetre.
This is 10 times bigger than current estimate.
In mid 1860’s Austrian chemist Johann Loschmidt estimated this size of air molecules,
to be a few millionth of a metre.
He also estimated Avogadro’s number to be .5 into 10 power 23.
He also estimated, number of molecules in a cubic metre of gas.
Now this is known as Loschmidt’s number, whose modern value is 2.687673 into 10 power 25.
To study molecules, Einstein used liquids like sugar in water, and phenomenon of osmosis.
The container half full with water, has a membrane with holes,
just enough to allow molecules of water to pass through.
If sugar is dissolved in one side of this container, water moves through the membrane into the solution,
diluting the strength of the solution.
According to the second law of thermodynamics differences in the universe, tend to average out.
In this experiment, the level of liquid where the sugar is, tends to rise.
The osmotic pressure is calculated, by measuring the height difference.
The osmotic pressure depends on the number of sugar molecules in the solution.
The more concentrated the solution, the greater is the pressure.
Einstein used this to calculate Avogadro’s number as 2.1 into 10 power 23.
He estimated that water molecules must be a few hundred millionths of a centimetre.
He later revised the Avogadro’s number to 6.6 into 10 power 23.
The second part of Einstein’s paper concerned the phenomenon known as Brownian motion.
Brownian motion gets its name from the Scottish botanist Robert Brown,
who noticed the phenomenon while studying pollen grains through a microscope in 1827.
Later in the 19th century French physicists Louis Georges Gouy and William Ramsay in England,
suggested a better way to explain Brownian motion in statistical terms.
Einstein had no idea of these suggestions.
Einstein was notorious for working ideas out for himself from first principles,
without throughly reading the published literature of the subject.
Einstein independently worked out the statistics behind Brownian motion.
He made a prediction based on the molecular kinetic theory, which could be tested by microscopists,
who observed Brownian motion in sufficient detail.
Einstein came up with an equation that linked Avogadro’s number,
with the speed with which molecules move.
The Frenchman Jean Perrin accurately measured this very minute movement,
of 6000th of a millimetre, in one minute.
This provided proof of the reality of atoms and molecules, for which he received the Nobel prize in 1926.
In 1910, Einstein wrote a paper explaining how the blue colour of the sky is caused.
It is caused by the way light is scattered by the molecules of gas in the air.
Blue light is more easily scattered, than red or yellow light.
This is why the blue light from the sun comes to us from all directions in the sky.
It is bounced from molecule to molecule in the sky, while the direct light from the sun is orange.
In 1869, John Tyndall discussed scattering of light, related to dust.
When there is dust in the air, the dust takes out even more of the blue from sunlight.
This is the reason that the sun seems reddish at sunrise and sunset.
Other scientists suggested that it is the molecules in the air, not the dust, that causes the sky to be blue.
It was Einstein, who used the blueness of the sky to calculate Avogadro’s constant in another way.
He also provided supporting evidence for the reality of atoms, and molecules.
Einstein is best remembered for his work on light, in a much more fundamental way.
In order to set a special theory of relativity in context, we need to go back to see,
how the understanding of the nature of light, developed in the 19th century.
This led Einstein to appreciate the need for a modification to the most hallowed maxims of science,
Newton’s Law of Motion.