Science: A History

Origins

• One potential date for the beginning of the revival of Western Europe is 1453:
  • Publication of "On the Structure of the Human Body" by Andreas Vesalius and of "On the Revolutions of the Celestial Bodies" by Copernicus", mark the start of the scientific revolution that would transform first Europe and then the world.
  • The Turks captured Constantinople marking the end of the old Roman Empire, causing many Greek-speaking scholars fled westwards to Italy with their documents, and there the Italian humanists took up these documents and the teaching found therein to -establish civilization along the lines that head existed before the Dark Ages.
  • Perhaps equally important was the depopulation of Europe by the Black Death in the 14th C, which led the survivors to question the whole basis of society, made labor expensive and encouraged the invention of technological devices to replace manpower.
  • Also, Gutenberg's development of moveable type in the mid 15th C had an obvious impact on what was to become science, and discoveries brought back to Europe by another technological development, sailing ships capable of crossing the oceans, transformed society.
• The scientific revolution did not happen in isolation, but eventually became the driving force of Western civilization over the next 450 years.
• The development of technology is more important than human genius, and it is no surprise that the start of the scientific revolution "coincides" with the development of the telescope and the microscope.
• Western science got started because the Renaissance happened. And once it got started by giving a boost to technology it ensured that it would keep on rolling, with new scientific ideas leading to improved technology, and improved technology providing the scientists with the means to test new ideas to greater and greater accuracy. Technology came first, because it is possible to make machines by trial and error without fully understanding the principles on which they operate. But once science and technology got together, progress really took off.

Renaissance Men

• Nicolaus Copernicus (1473-1543) - "On the Revolution of the Celestial Spheres" (1543)
• Andreas Vesalius (1514-1564) - "On the Structure of the Human Body" (1543)
• William Harvey - discovery of the circulation of the blood.
• Gabriele Fallopio - discover of the fallopian tubes

The Last Mystics

• Tycho Brahe (1546-1601) - De Nova Stella (1573)
  • Sees a comet in 1577. First astronomer to imagine the planets hanging unsupported in space
• Johannes Kepler (1571-1630) - The Mystery of the Universe (1597)
  • Suggested that planets were kept moving in their orbits by a force he called "the vigour" reaching out from the Sun and pushing them along.
  • "My aim is to show that the machine of the universe is not similar to a divine animated being, but similar to a clock."
  • First and second laws about planetary orbits.
  • "Astronomia Nova" (1609)
  • "Harmony of the World" (1618) - Third law about planetary orbits
  • Writes one of the first science-fiction stories, "Dream of the Moon
• John Napier (1550-1617) - Invented logarithms

The First Scientists

• William Gilbert (1544-1603)
  • Concerning Magnetism, Magnetic Bodies, and the Great Magnet Earth (1600)
  • Discovered laws of attraction and repulsion, that the Earth acts like a magnet, names the north pole and south pole
  • Nothing new was discovered about magnetism until the discovery of electromagnetism in the 1820s
  • Galileo described Gilbert as the founder of the experimental method of science.
• Galileo Galilei (1564-1642)
  • Always carried out experiments to test hypotheses, modifying or abandoning those hypotheses if the outcomes of the experiments did not match their predictions.
  • Also investigated hydrostatics, magnetism
  • Proved that a bullet fired from a gun describes a parabola
  • Built a telescope better than any other in just 24hrs
  • Discovered the four largest moons of Jupiter early in 1610, that the Milky Way is made up of many individual starts, and that the surface of the Moon is scarred by craters and has mountain ranges several km high in book The Starry Messenger (1610)
  • He was willing to test his reasoning by clearly thought-out experiments, in public, and to stand by the results.
  • Was one of the first to develop an effective compound microscope, involving two lenses each ground with a doubly convex shape.
  • Dialogue on the Two Chief World Systems (1629)
  • Discourses and Mathematical Demonstrations Concerning Two New Sciences (1638) - summed up his life’s work on mechanics, inertia, and pendulums and the strength of bodies, as well as spelling out the scientific method. The first modern scientific textbook, spelling out that the Universe is governed by laws which can be understood by the human mind and is driven by forces whose effects can be calculated using maths.
  • Realized that moving objects have a natural tendency to keep on moving, unless they are affected by friction or some other outside force.

Science Finds its Feet

• The symbols + and - were only introduced to maths in 1540 in Robert Recorde’s « The Grounde of Artes
• In another book, « Whetstone of Witte » (1557), he introduced the equals sign.
• The multiplication symbol was introduced in 1631, and the division symbol in 1659.
• The introduction of logarithms early in the 17th C enormously simplified and speeded up the laborious processes of calculations for astronomers and other scientists.
• Logarithms are a way to "undo" exponentiation. If $b^y = x$, then we say that the logarithm base $b$ of $x$ is $y$, written as $\log_b(x) = y$. In simpler terms, a logarithm answers the question: "To what power must I raise the base $b$ to get the number $x$?"

For example, since $10^2 = 100$, we know that $\log_{10}(100) = 2$. Here, 10 is the base, 100 is the number, and 2 is the logarithm (or the exponent).

Logarithms are incredibly useful for simplifying complex calculations, especially those involving very large or very small numbers. They turn multiplication into addition, division into subtraction, and exponentiation into multiplication. This made them invaluable before the age of calculators and continues to be important in various fields like science, engineering, and finance.

• Réné Descartes (1596-1650)
  • A Discourse on the Method of Rightly Conducting Reason and seeking Truth in the Sciences (1637)
  • Cartesian co-ordinates (x,y) allowed geometry to be analyzed using algebra
  • Mediationnes de Prima Philogsophia (1641)
  • Principia Philosophiae (1644)
• Blaise Pascal (1623-1662)
• Pierre Gassendi (1592-1655) - revived the concept of atomism, which dates back to Democritus in the 5th C BC
• Evangelista Torricelli (1608-1647) - invented the barometer and created a vacuum
• Christiaan Huygens (1629-1695) - from 1658 allows ordinary people to have access to accurate timepieces.
  • Uses the Aether to explain how light is refracted
  • Treatise on Light (1690)
• Royal Society is founded in London in 1645, In Paris, the Académie des Sciences in 1667
• Ole Romer (1644-1710) Calculated the speed of light as 225,000km/s, very close to the modern calculation of 299,792km/s
• Robert Boyle (1627-1691)
  • « We assent to experience, even when its information seems contrary to reason. »
  • The Spring of the Air (1660) - treats air pumpts and the problem of raising water by suction. Boyle’s la. Seen as a turning point for chemistry.
  • Came close to discovering Oxygen - essential similarities between the processes of respiration and combustion.
  • His most famous book, The Sceptical Chymist (1661)
  • Origin of Forms and Qualities (1666)
• Marcelo Malpighi (1628-1694) - Circulation of the blood
• Giovanni Borelli (1608-1679)
  • On the Movement of Animals (1680-1681) - treated the body as a system of levers acted on by the forces exerted by the muscles, and analysed geometrically how muscles in the human body acted in walking and running.
• Edward Tyson (1650-1708) - founding father of comparative anatomy
  • Anatomy of a Porpess
  • Orang-Outang - evidence that humans and chimps were built to the same body plan. The place of human beings as part of the animal kingdom is clearly established.

The Newtonian Revolution

• Robert Hooke (1635-1703):
  • Micrographia (1665) - the first subtantial book on microscopy by any major scientist. Marked the moment when microscopy came of age as a scientific discipline. Included the "cellular" structure of slices of cork - first use of the word cell
  • He realized that the orbital motion results from the tendency of the Moon to move in a straight line, plus a single force pulling it toward the Earth.
• Isaac Newton (1643-1727):
  • Calculus makes it possible to calculate accurately, from a known starting situation, things that vary as time passes, such as the position of a planet in its orbit. Provided the mathematical tools needed to study processes in which change occurs. Modern physical science simply would not exist without calculus.
  • Newton wondered whether, if the influence of the Earth's gravity could extend to the top of the tree, it might extend all the way to the Moon. He then calculated the force required to hold the Moon in its orbit and the force required to make the apple fall from the tree could both be explained by the Earth's gravity if the force fell off as one over the square of the distance from the centre of the Earth.
  • Principia Mathematica (1687) - He laid the foundations for the whole of physics, not only spelling out the implications of his inverse square law of gravity and the three laws of motion, which describe the behavior of everything in the Universe, but making it clear that the laws of physics are indeed universal laws that affect everything. The realization that the world works on essentially mechanical principles that can be understood by humand beings, and is not run in accordance with magic or whims of capricious gods.
  • Opticks (1704)

Expanding Horizons

• In the century after Newton, there was a huge expansion of the realm which science attempted to explain.
• Edmond Halley (1656-1741):
  • Questioned the accepted date of the Creation, 4004 BC
  • Studied variations in atmospheric pressure and winds
  • Experimented with a diving bell to a depth of 18m
  • 1698 Voyage of the Paramore for a year to the South Atlantic
  • "A Synopsis of the Astronomy of Comets" (1705)
  • Flamseed's star catalogue containing 3,000 star positions (1725)
  • 1720 Appointed as Astronomer Royal
  • Correctly predicted the return of Halley's comet after his death in 1758-9 and transits of Venus in 1761 and 1769. These latter were used to work out the distance to the Sun at 153m km, very close to the modern measurement of 149.6m km.
• John Ray (1627-1705) - the biological equivalent of Newton:
  • Ornithology (1677)
  • History of Fishes (1686)
  • History of Plants (1686, 88, 1704) - covering 18,000 plants, classified plants in terms of their family relationships, morphology, distribution and habitats.
  • Established the species as the basic unit of taxonomy
  • History of Insects (1710)
  • Made the study of botany and zoology a scientific pursuit, bring order and logic to the investigation of the natural world
  • Invented a clear taxonomic system based on physiology, morphology, and anatomy, paving the way for the work of Linnaeus.
• Carl Linnaeus (1707-1778)
  • Plants reproduced sexually and had male and female parts
  • Could not understand anything that is not systematically ordered.
  • Systema Naturae (1735) - Introduces the binomial system of classifying every species with a two-word name. Introduced the terms Mammalia, Primates, and Homo sapiens.
  • Provided descriptions of 7700 species of plants and 4400 species of animals. Everything in the living world was arranged in a hierarchy of family relationships, from the broad classifications of their Kingdom and class down through the subdivisions Order and Genus to the Species itself. This systm preserves the last vestige of Latin in scientific work right up to the present day.
  • Paved the way from which the relationships between species and the laws of evolution would begin to become clear in the 19th C.
  • Was the first person to include man in a system of biological classification. I have yet to find any characteristics which enable man to be distinguished on scientific principles from an ape
  • Nowadays, using DNA evidence, man would be classified as a chimpanzee.
• Anders Celsius (1701-1744)
• Nicolaus Steno (1638-1686)
• Comte de Buffon (1707-1788):
  • Histoire Naturelle in 44 volumes between 1749-1804 - the first work to cover the whole of natural history
  • Speculated that the Earth had formed out of material thrown out of the Sun as the result of the impact of a comet.
  • Calculated that the Earth must be at least 75k years old
• Jean Fourier (1768-1830):
  • Fourier Analysis - mathematical techniques for dealing with time-varying phenomena
  • Developed sets of equations to describe heat flow
  • Calculated the age of the Earth as 100m years
• Georges Couvier (1769-1832)
  • Lectures in Comparative Anatomy (1800)
  • Probably the most influential biologist in the world in the 1830s
  • Compared the bodies of meat-eating and plant-eating animals
  • Arranged all animals into four major groups (vertebrates, molluscs, articulates, and radiates), which each had its own kind of anatomy.
  • Almost single-handedly invented the science of paleontology - could say which strata of fossils was older and younger
  • Discours sur la Théorie de la Terre (1825)
• Jean-Baptiste Lamarck (1744-1829) - urged naturalists to describe the natural world, without wasting time on theories purporting to explain it.

Enlightened Science I: Chemistry Catches Up

• The basic feature of the Enlightenment was a belief in the superiority of reason over superstition. This incorporated the idea that humankind was in the process of progressing socially, so that the future would be an improvement of the past; and one of those improvements was a challenge to orthodox religion with its overtones of superstition. Both the American and the French revolutions were justified intellectually, in part, on the basis of human rights, a guiding principle of Enlightenment philosophers such as Voltaire and activists such as Thomas Paine. The success of Newtonion physics in providing a mathematical description of an ordered world clearly played a big part in the flowering of this movement in the 18th century, encouraging philosophers of a rationalist persuasion, and also encouraging chemists and biologists to think that their parts of the natural world might be explained on the basis of simple laws.
• The idea of order and rationality as a way to investigate the world had taken root by the early 18th C and seemed the obvious way forward.
• The Industrial Revolution probably took place first in England (around 1740-1780 due to Britain being an « island of coal » but also because the Newtonian mechanistic world became firmly established there. The IR stimulated interest in topics like heat and thermodynamics (the connection between heat and motion) and provided new tools for scientists to use in their investigations of the world.
• Astronomy, physics, botany, and zoology could make progress with simple tools, but chemists needed, above all, a reliable and controllable source of heat to encourage chemical reactions.
• Gabriel Fahrenheit (1686-1736)- Invented the alcohol thermometer in 1709, the mercury thermometer in 1714 (along with the Fahrenheit scale).
• Anders Celsius (1701-1744) - came up with his scale in 1742.
• Thomas Newcomen (1663-1729) - Completed the first practical steam engine to pump water from mines in 1712
• From the 1740s onward, progress was rapid (if sometimes confused).
• William Cullen (1710-1790) - Invented the first refrigerator.
• Joseph Black (1728-1799):
  • Discovered carbon dioxide and showed for the first time that air is a mixture of gases and not a single substance.
  • Using his usual careful, quantitative approach, made a crucial distinction between the concepts of heat and temperature.
  • Gave the name « specific heat » to the amount of heat required to raise the temperature of a certain amount of a chosen substance by a certain amount.
• James Watt (1736-1819)
  • First person to take a set of ideas from the cutting edge of then-current research in science and apply them to make a major technological advance.
  • The scale effect - a small object loses heat more rapidly than a large object of the same shape because the small object has a larger surface area, across which heat escapes, in proportion to its volume, which stores heat.
• He improved on Newcomen’s steam engine by using two cylinders, one which was kept hot (in which the piston moved) and one which was kept cold.
  • Patented his steam engine in 1769.
• Joseph Priestley (1733-1804):
  • Wrote a history of electricity in1767.
  • When he began, only two gases (« air » and carbon dioxide (« fixed air ») were known.
  • Identified another ten gases, including ammonia, hydrogen choloride, nitrous oxide (laughing gas) and sulphur dioxide.
  • Greatest discovery was Oxygen (in 1774) - explaining it in terms of the philogiston model. This model would be doomed when people started noticing that things get heavier when they burn, not lighter.
  • Discovered carbon dioxide over a brewers vat and invented « soda water », a craze for which spread across Europe.
  • Showed how the ability of air to sustain life would somehow be « used up » in respiration and that the respirability of the air could be restored by the presence of planes - the first hints of the process of photosynthesis in which carbon dioxide is broken down and oxygen is released.
• Carl Scheele (1742-1786) - Realized that air is a mixture of two substances, one of which prevents burning, while the other promotes combustion.
• Science progresses incrementally, building on what has already been discovered and making use of the technology of the day.
• Henry Cavendish (1731-1810):
  • The Cavendish Laboratory in Cambridge, built in the 1870s is named after him.
  • Discovered Hydrogen (« inflammable air ») in 1776. He thought that the gas was released by the metals involved in the reaction (we now know that it comes from the acids), and thought that it was phlogiston.
  • Showed that water was not an element and is somehow formed from a mixture of two other substances, a key step in the transformation of alchemy into chemistry.
  • Found a previously unknown gas, argon, present in tiny traces (0.93%) in the atmosphere.
  • In « the Cavendish experiment », weighed the Earth using a torsion balance.
• Antoine Lavoisier (1743-1794):
  • Thought of as the greatest chemist of all
  • Showed that diamond is combustible.
  • Showed that sulphur gains weight when it burns, his first, independent, step to the modern understanding of combustion as a process involving oxygen from the air combining with the substance that is being burnt.
  • Gave oxygen its name (in 1779)
  • Coming towards the idea that animals keep warm by converting carbon (from their food) into carbon dioxide (which they breathe out) by combining it with oxygen from the air (which they breathe in), seeing respiration as a very slow form of combustion. This was a key step in setting human beings in their context as complicated systems obeying the same laws as falling stones or burning candles, and showed that there was no need to invoke anything outside the known world of science to produce the life-associated warmth of the human body - no need for Harvey’s « natural heat ».
  • First person to appreciate that water is a compound substance formed from a combination of « inflammable air » and oxygen in the same sort of way that « fixed air » is formed from a combination of carbon and oxygen.
  • Elements of Chemistry (1789) - which laid the foundations for chemistry as a genuinely scientific discipline and almost an equivalent to chemistry of newton’s Principia to Physics. Marks the moment when chemistry becomes recognizable as the discipline of today.
  • Proposed new names based on a logical system of nomenclature (such as oxygen, hydrogen, and sulphuric acid), introduced a logical way to name compounds, such as nitrates. By giving chemistry a logical language, he greatly eased the task of chemists trying to communicate their discoveries to one another.
  • Guillotined on 8 May 1794.

Enlightened Science II: Progress on All Fronts

• In the decade following the death of newton, the term « Physics » started to be used in plae of « natural philosophy.
• Pieter van Musschenbrook (1692-1761):
  • « Essaie de Physique » (1737 - one of the first books to use the term in its modern sense
  • Invented the Leiden Jar - a device that could store large quantities of electricity
• First steps towards an understanding of static elecricity.
• There are two kinds of electricity (positive and negative charge) and similar kinds repel one another while opposite kinds attract.
• The importance of insulating material in preventing electricity draining away from charged objects.
• Benjamin Franklin (1706-1790):
  • Developed a one fluid model of electricity where a physical transfer of the single fluid occurs when an object becomes electrically charged, leaving one surface with « negative » charge and the other with « positive » charge. ie, charge is conserved - there is always the same amount of electricity, but it can be moved around, and overall the amount of negative charge must balance the amount of positive charge.
  • Showed that electricity can magnetize and demagnetize iron needles.
• Charles Coulomb (1736-1806) - Convinced everyone that both electrical and magnetic forces obey an inverse square law - now coulomb’s law.
• Luigi Galvini (1737-1è98) - twitching of frog’s legs is caused by electricity stored or manufactured in the muscles of the frog.
• Alessandro Volta (1745-1827):
  • Created the voltaic pile, forerunner of the modern battery. Beore this, the study of electricity was essentially confined to the investigation of static electricity. After 1800, physicicists could work with electric currents, which they could turn on and off at will.
  • Current from such a pile could be used to decompose water into hydrogen and oxygen.
• Pierre-Louis de Maupertuis (1698-1759):
  • The principle of least action - nature is lazy. Eg, light always travels in straight lines.
• Leonhard Euler (1707-1783) - regarded as the most prolific mathematician of all time.
  • Introduced the use of the letters e and i
  • Described mathematically the refraction of light.
• William (1738-1822) and Caroline (1750-1848) Herschel discovered Uranus, the first planet that had not been known to the ancients.
• John Michell (1724-1793) - first person to come up with the idea of what are now known as black holes in a paper read to the Royal Society in 1783.
• Pierre Simon Laplace (1749-1827)
  • Explained variations in planetary orbits follow a cycle 929 years long (so the Solar System is stable after all.
  • Exposition du système du monde (1796) - one of the most influential books about science ever published, summing up where physics stood at the end of the 18th C. « The simplicity of nature is not to be measured by that of our conceptions. Infinitely varied in its effects, nature is simple only in its causes, and its economy consists in producing a great number of phenomena, often very complicated, by means of a small number of general laws.
  • Nebular hypothesis of the origin of the Solar System - it was practically certain that the planets had formed together from a cloud of material around the young Sun, shrinking down into a plane as the cloud, or nebula, contracted.
  • Laplace’s version of black holes.
• One reason why science did progress so rapidly in the 19th C was that by the end of the 1790s it was obvious to all but the most blinkered of the old school that the ideas of phlogiston and caloric wer both dead and buried.
• James Hutton (1726-1797):
  • Develops the idea of uniformitarianism - that the same uniform processes are at work all the time and mould the surface of the Earth continually. The idea that occasional great acts of violence are needed to explain the observed features of the Earth become known as catastrophism. Previously the received wisdom was a combination of catastrophism and Neptunism.
  • Theory of the Earth (1795). John Playfair wrote a masterly, clear summary of it in 1802 as Illustrations of the Huttonian Theory of the Earth.

The Darwinian Revolution

• Arguably the most important idea in the whole of science. This is the nub of the theory of natural selection:
  • Offspring resemble their parents, but in each generation there are slight differences between individuals.
  • Only the individuals best suited to the environemnt survive to reproduce, so the slight differences which make them successful are selectively passed on to the next generation and become the norm.
  • When conditions change, or when species colonize new territory, species change to match the new conditions and new species arise as a result.
  • Natural selection explains how, given enought time, evolution could produce an antelope adapted to a grazing lifestyle, the grass itself, a lion adapted to eat antelope, a bird that depends on a certain kind of seed for its food, or any other species on Earth today, including humankind, from a single, simple common ancestor.
• Charles Lyell (1797-1875):
  • Principles of Geology (1830) - Third volume in 1833, 12th and final in 1875
  • The first person to make his living as a science writer.
  • Elements of Geology (1838)
  • The leading geologist of his time
  • In 1841 went on a year-long visit to the US by steamship, and was surprised how the railways had already spread over what was until recently unknown territory.
• Evolutionary ideas can be traced back to the ancient Greeks, and there were discussions about species change by Francis Bacon in 1620 and Leibnitz, while Buffon also discussed the migration and evolution of species. The difference with Darwin and Russel was that they came up with a sound scientific theory.
• Erasmus Darwin (1731-1802):
  • Zoonomia (1794, 1796) in two volumes sets out his ideas on evolution.
  • God still exists for Erasmus, but only as the first cause who set the processes of life on Earth working. There is no place here for a God who intervenes to create new species from time to time, but a clear sense that whatever the origins of life itself, once life existed it evolved and adapted in accordance with natural laws, with no outside intervention.
• Jean-Baptiste Pierre Antoine de Monet de Lamarck (1744-1829):
  • Flore française (1778)
  • Classified insects and worms into « invertebrates ».
  • Histoire naturelle des animaux sans vertèbres (7 volumes) (1815-1822):
  • His four laws - which become progressively more wrong:
    • First law - By virtue of life’s own powers there is a constant tendency for the volume of all organic bodies to increase and for the dimensions of their parts to extend up to a limit determined by life itself. (true)
    • The production of new organs in animals results from newly experienced needs which persist, and from new movements which the needs give rise to and maintain (not wrong but Lamarck means, wrongly, that the new organs develop within individuals, not by tiny changes from one generation to the next)
    • Third Law: The development of organs and their faculties bears a constant relationship to the use of the organs in question (definitely wrong - the idea that the giraffe’s neck gets long because it is stretching for leaves)
    • Fourth Law: Everything which has been acquired or changed in the organization of an individual during its lifetime is preserved in the reproductive process and is transmitted to the next generation by those who experienced the alterations (definitely wrong)
• Charles Darwin (1809-1882)
  • Learned about the argument between the Neptunists, who thought that the Earth’s features had been shaped by water, and the Vulcanists, who saw heat as the driving force - he preferred the latter explanation.
  • 1831 - start of a 5 year voyage on the Beagle
  • The Voyage of the Beagle (1839)
  • Calls the great age of the Earth, « the gift of time »
  • On the Origin of Species by Means of Natural Selection (1859) - prompted by Lyell’s advances
• Thomas Malthus (1766-1834):
  • Britain’s first professor of political economy.
  • Essay on the Principle of Population (1798) - populations have the power to grow geometrically, but are held in check by pestilence, predators, and especially by the limited amount of food available (as well as by war, in the case of humans). Most offspring die without reproducing, if nature takes its course.
• Alfred Russel Wallace (1823-1913)
  • 1847 - self-funded a four year , two-man expedition to South America, exploring and collecting in the jungles of Brazil.
  • The great problem of the origin of species was already distinctly formulated in my mind… I firmly believed that a full and careful study of the facts of nature would ultimately lead to a solution of the mystery
  • 1854 - goes to the Far East because he decided that the best way to pursue his interest in the species problem would be to visit a region of the globe which had not already been explored by other naturalists.
  • Stays there for eight years, publishing 40 scientific papers, and establishing the geographical ranges of different species
  • Wallace developed the idea of evolution as like the branching of a huge tree, with different branches growing from a single trunk, and continually dividing and splitting down to the little twigs, still growing, which represent the diversity of living species (all derived from a common stock) in the world today. He presented these ideas in 1855 without, at that point, offering an explanation for how or why speciation occurred.
  • Breakthrough in 1858, remembering Malthus - in every generation the inferior would inevitably be killed off and the superior would remain.
  • On the Tendency of Varieties to Depart Indefinitely from the Original Type (1858)
• Thomas Henry Huxley (1825-1895)
  • Darwin’s bulldog
  • Helped to establish science as a profession that people were paid to do.
• Darwin was the first scientist listed here who was born after 1800. Wallace was the first who dies after 1900.

Atoms and Molecules

• During the 19th C, science shifts from being a gentlemanly hobby to a well-populated profession
• Humphry Davy (1778-1829):
  • Learned French and red Lavoisier’s Traité Elémentaire in the original French
  • Carried out experiments with nitrous oxide (laughing gas) and discovered that it could be used during surgical operations
  • Saw a significant relationship between chemistry and electricity.
  • Royal Instituation established by Count Rumford in 1799 and he became its director in 1802
  • One of the last great amateur scientists and also one of the first professional ones.
  • 1806 - Isolated two previously unknown metals and called them potassium and sodium.
  • 1810 - isolated and named chlorine. Defined an element as a substance that cannot be decomposed by any chemical process, showed that chlorine is an element, and established that the key component of all acids is hydrogen, not oxygen.
  • Appointed Michael Faraday (his eventual successor) as an assistant in the RI
  • Designed the famous miners’ safety lamp which bears his name.
  • In 1820, elected President of the Royal Society
• John Dalton (1766-1844)
  • When he was born, there were perhaps 300 scientists in the world, when he started work there were a thousand, by his death 10k, and by 1900 100k. The number of scientists doubled every 15 years (though generally populations were doubling over longer periods)
  • Recorded daily meteorological observations daily from 1787 until his death.
  • Discussed the nature of water vapour and its relationship to air, describing it in terms of particles which exist between the particles of air, so that the equal and opposite pressures of the surrounding air particles on a particule of vapour cannot bring it nearer to another particle of vapour, without which no condensation can take place - a precursor to his atomic theory.
  • Was color-blind and did a detailed analysis of the condition, which became known as Daltonism
  • In 1801, came up with the law of partial pressures, which says that the total pressure exerted by a mixture of gases in a container is the sum of the pressures each gas would exert on its own under the same conditions.
  • In the early 1800s became convinced that each element was made up of a different kind of atom, what made one element different from another was the weight of its atoms, and that elementary atoms could be neither created nor destroyed (though they could combine to form « compound atoms » (molecules).
  • The main flaw in the model is that he did not realize that elements such as hydrogen are composed of molecules, not individual atoms and so he got some combinations wrong.
  • A New System of Chemical Philosophy (1808)
• It took almost half a century for the Daltonian atom to become really fixed as a feature of chemistry
• Jöns Berzelius (1779-1848):
  • One of the first people to formulate the idea that compounds are composed of electrically positive and negative parts
  • Studied 2000 different compounds over 6 years
  • Invented the modern alphabetical system of nomenclature for the elements.
  • Isolated and identified several elements, including selenium, thorium, lithium and vanadium
  • Chemists were beginning to group elements into families with similar properties. He gave the name « halogens » (meaning salt-formers) to the group including chlorine, bromine, and iodine.
  • Coined the terms « organic chemistry », « catalysis », and « protein »
  • Textbook of Chemistry (1803)
  • Experimenters had long been aware that everything in the material world falls into one of two varieties of chemical substances. Some can be heated and seem superficially to change their character (glowing red hot, melting, evaporating, etc), but when cooled, revert back to the same chemical state they started from. Others, such as sugar or wood, are completely altered by the action of the heat, so that it is very difficult to « unburn » a piece of wood. In 1807, he formalized the distinction. The first, associated with non-living systems, he called « inorganic », and the second, associated with living systems, « organic ». It became clear that organic materials are made up of much more complex compounds, but there was also belief in a vague « life force ».
• Joseph Louis Gay-Lussac (1778-1850)
  • In 1809 published that gases combine in simple proportions by volume, and that the volume of the products of the reaction (if they are also gaseous) is related in a simple way to the volumes of the reacting gases.
• Amadeo Avogadro (1776-1856):
  • In 1811, gave the hypothesis that at a given temperature, the same volume of any gas contains the same number of particles.
  • Realized that oxygen and other elements could exist in polyatomic molecular form. Two volumes of hydrogen contain twice as many molecules as one volume of oxygen, and when they combine, each oxygen molecule provides one atom to each pair of hydrogen molecules, making the same number of molecules as there were in the original volume of Hydrogen.
• William Prout (1785-1850):
  • Suggested that the atomic weights of all elements are exact multiples of the atomic weight of hydrogen, implying that in some way heavier elements might be built up from hydrogen.
  • In the 20th C, with the discovery of isotopes (atoms of the same element with slightly different atomic weights, but each isotype having an atomic weight a precise multiples of the weight of one hydrogen atom) the puzzle was resolved (since chemically-determined atomic weights are an average of those of all the isotopes of an element present, and Prout’s hypothesis was confirmed.
• Friedrich Wöhler (1800-1882):
  • Accidentally discovered that organic materials could be manufactured from substances that had never been associated with life and the definition of organic changed. There was no mysterious life force.
  • Organic compounds are often complex, containing elements of different elements, and they all contain carbon, which is the reason for their complexity.
• Now we say that an organic molecule is any molecule containing carbon and organic chemistry is the chemistry of carbon and its compounds. Life is seen as a product of carbon chemistry, obeying the same chemical rules that operate throughout the world of atoms and molecules. Natural selection tells us that we are part of the animal kingdom with no evidence of a uniquely human soul. Chemistry tells us that animals and plants are part of the physical world, with no evidence of a special « life force ».
• Edward Frankland (1825-1899)
  • Analyzed valency, a measure of the ability of one element to combine with another or as soon became clear, the ability of atoms of a particular element to combine with other atoms.
• Archibald Couper (1831-1892):
  • Introduced the concept of « bonds », simplifying the representation of valency. Hydrogen is now said to have a valency of 1, meaning that it can form one bond with another atom. Oxygen has a valency of 2, meaning that it can form two bonds. Nitrogen has a valency of 3 and carbon has a valency of 4, so it can form four separate bonds with four separate atoms, including other atoms of carbon at the same time.
  • He saw that organic chemistry might consist of a chain of carbon atoms holding hands with other atoms attached to the spare bonds at the sides of the chain.
• Friedrich August Kekulé (1829-1896):
  • Saw that carbon atoms could link up in rings (often six atoms in a hexagon) with bonds sticking out from the ring to link up with other atoms or other rings of atoms.
• Stanislao Cannizzaro (1826-1910)
  • Drew the essential distinction between atoms and molecules
  • Showed how the observed behavior of gases together with Avogadro’s hypothesis could be used to calculate atomic and molecular weights relative to the weight of one hydrogen atom, and drew up a table of atomic and molecular weights.
• John Newlands (1837-1898):
  • Realized that if the elements are arranged in order of their atomic weight, there is a repeating pattern in which elements at regular intervals, with atomic eights separated by amounts that are multiples of eight times that of hydrogen, have similar properties.
• Dmitri Mendeleev (1834-1907):
  • Principles of Chemistry (1868, 1870)
  • On the Relation of the Properties to the Atomic Weights of Elements
  • Rearranges the elements slightly in order to make them fit the pattern he had discovered and leaves gaps in the periodic table for elements which had not yet been discovered.
  • It turns out that the chemical properties of an element depend on the number of protons in the nucleus of each atom (the atomic number), while its atomic weight depends on the total number of protons plus neutrons in the nucleus
  • By 1871 he had refined his table to incorporate all of the 63 known elements, with three gaps, which would be filled over the next 15 years with just the properties predicted by him - gallium (1875), scandium (1879) and germanium (1886)
  • From a mass of data, Mendeleyev found a pattern and made a prediction that could be tested by experiment, and found a deep truth about the nature of the chemical world.
• Themodynamics frew out of the industrial revolution and fed back into it. At the beginning of the 19th C, there was no consensus about the nature of heat, the term was coined in 1849 by William Thomson, by the 1860s the basis laws and principles had been worked out, and 40 years later would be used in a definitive proof of the reality of atoms.
• Sadi Carnot (1796-1832)
  • Réflexions sur la puissance motive du feu (1824) - analyzed the efficiency of engines converting heat into work, provided a scientific definition of work, showed that work is done as heat passes from a higher temperature to a lower temperature, and even suggested the possibility of the internal combustion engine.
  • First person to appreciate that heat and work are interchangeable and worked out how much work a given amount of heat can do.

Julius Robert von Mayer (1814-1878):

• • Knew Lavoisier’s work which showed that warm-blooded animals are kept warm by the slow combustion of food, which acts as fuel, with oxygen in the body. He knew that bright red blood, rich in oxygen, is carried around the body from the lungs in arteries, while dark purple blood, deficient in oxygen, is carried back to the lungs by veins.
  • Realized that the reason why the venous blood was rich in oxygen was that in the heat of the tropics the body had to burn less fuel (and therefore consume less oxygen) to keep warm. He saw that this implied that all forms of heat and energy are interchangeable - heat from muscular exertion, the heat of the Sun, heat from burning coal, or whatever - and that heat, or energy, could never be created but only changed from one form to another.
• James Joule (1818-1889):
  • Gave two lectures in Manchester in 1847 setting out the law of conservation of energy and its importance to the physical world.
  • The Joule-Thomson effect - the way in which gases cool as they expand, the principle on which a refrigerator operates.
• William Thomson/Lord Kelvin (1824-1907):
  • Responsible for the success of the first working transatlantic telegraph cable
  • Established thermodynamics as a scientific discipline in the middle of the 19th C.
  • Established the absolute scale of temperature, which is based on the idea that heat is equivalent to work, and that a certain change in temperature corresponds to a certain amount of work. There is a minimum possible temperature (-273C) at which no more work can be done because no heat can be extracted from a system.
• Laws of thermodynamics:
  • First law - heat is work
  • Second law - Heat cannot, of its own volition, move from a colder object to a hotter object. Things wear out - everything wears out, including the Universe itself
• Rudolf Clausius (1822-1888)
  • Defined « entropy ».