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Brief History of Modern Science


Brief History of Modern Science Discovery - A new method of acquiring knowledge was invented by a series of European thinkers from 1500 to 1700. – PowerPoint PPT presentation

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Title: Brief History of Modern Science

Brief History of Modern Science
  • Discovery - A new method of acquiring knowledge
    was invented by a series of European thinkers
    from 1500 to 1700. Among these thinkers are
    Copernicus, Galileo, Descartes, Kepler, and
  • Definition of Science- A special method and
    knowledge executed by practitioners of science
    called scientists.

Meaning of Science
  • Science is practiced by specially trained people
    with a specific world view. Scientists try to be
    objective, non-sentimental, unemotional, honest,
    and unbiased
  • Scientists work in laboratories where conditions
    are carefully controlled.
  • Scientists report their findings in peer-reviewed
    journals to other scientists
  • Scientists do not claim more than what they can

Philosophical Foundations of Science Originated
in the 17th century
  • Science removed animism as a physical
    explanation. Greek philosophers thought movement
    was a sign of life. Planets were moved by
    angels. Newtons 1st law of motion changed this
  • Science changed mans position from the center of
    the universe to its periphery. Mans place in
    the universe was seen as minor.

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Aristotelian Science
  • Theory of Matter
  • Matter stuff out of which things are made
  • In sublunary world (below the moon) there
  • are four elements or essences
  • earth, water, air, and fire.
  • These four elements never found pure always
  • Heavy things made out of earth
  • Light things made mix of water,air, and fire

Aristotelian Science
  • Above sun, planets are stars imbedded in the
    crystalline sphere
  • The crystalline sphere made out of pure
    quintessence ( 5th essence)
  • Different laws pertain the sublunary world than
    to the world above the moon

Archimedes (287-212 BCE )
  • Sicilian geometrician who calculated an accurate
    value for pp, demonstrated the relationship
    between the volume of spheres and cylinders,
    discovered methods for determining the center of
    gravity of plane figures, and provided a
    foundation for the science of hydrostatics.
    Archimedes also invented many ingenious machines,
    including a pump for raising water, effective
    levers and compound pulleys, and a mechanical
    planetarium. He died defending Syracuse against a
    Roman seige during the second Punic war.

Ptolemy Epicycles
more accurate measurement required more epicycles
Thomas Aquinas (1224-1274 )
  • Although matters of such importance should be
    accepted on the basis of divine revelation alone,
    Aquinas held, it is at least possible (and
    perhaps even desirable) in some circumstances to
    achieve genuine knowledge of them by means of the
    rigorous application of human reason. As embodied
    souls ( hylomorphic composites ), human beings
    naturally rely on sensory information for their
    knowledge of the world. Reading hint Although
    the rigidly formal structure of the Summa
    articles can be rather confusing to a modern
    reader, the central portion beginning with the
    words, " I answer that ..." is always a direct
    statement of Aquinas's own position.

Roger Bacon
  • Bacon, Roger (1214-1292 )English philosopher who
    translated many Aristotelean treatises from
    Arabic into Latin. Although passionately
    interested in alchemy and magic, Roger defended
    reliance upon mathematics and experimental
    methods for the improvement of human knowledge
    generally and theological understanding in
    particular in the Opus Maius (Greater Work )
    (1267) at and On Experimental
    Science (1268). His novel educational doctrines
    were supposed to violate the condemnation of 1277
    , and much of Roger's later work, including the
    Compendium Studii Theologiae (1292) was

Roger Bacon
  • Against authority of
  • Church
  • State
  • Commonly held opinion
  • Obstacles to truth
  • Frail and unsuitable authority
  • Long-held custom
  • Uninstructed popular opinion
  • Concealment of ignorance in apparent wisdom

Roger Bacon
  • Bacons advice To study Natural Philosophy, use
  • External experience, aided by instruments, and
    made precise by mathematics.

  • Roger Bacon
  • The result of all true philosophy is to arrive
    at a knowledge of the creator through knowledge
    of the created world
  • He who wishes to rejoice without doubt in
    regard to the truths underlying phenomena must
    know how to devote himself to experiment. For
    authors write many statements, and people believe
    them through (deductive) reasoning, which they
    formulate without experience. Their reasoning is
    wholly false (Opus Majus)

William of Ockham,
  • Ockham, William of (1285-1349 )English
    philosopher who defended the logic, physics, and
    metaphysics of Aristotle in Summa Logicae (The
    Whole of Logic ) (1328) vol. 1 at
    and vol. 2 at and the Dialogus .
    An extreme nominalist , Ockham held that general
    terms are signs that indefinitely signify
    discrete (though similar) particulars. Ockham is
    best known for his statement of the law of
    parsimony as the ontological principle often
    called Ockham's Razor " Frustra fit per plura
    quod potest fieri per pauciora " "It is
    pointless to do with more what can be done with
    less". Thus, according to Ockham, we ought never
    to postulate the reality of any entity unless it
    is logically necessary to do so.

William of Ockham
  • Ockhams Razor
  • What can be accounted for by fewer assumptions
    in explained in vain by more.
  • His philosophy of science
  • Nothing is assumed as evident unless it is
    known per se or is evident by experience, or is
    proved by authority of scripture.

Paracelsus (Phillippus Aureolus Theophrastus
Bombastus von Hohenheim) ( 1493-1541 )
  • Swiss chemist and physician. Rejecting the
    ancient reliance on concern for bodily "humours,"
    Paracelsus transformed the practice of medicine
    by employing careful observation and
    experimentation. Although his chemical knowledge
    was rudimentary by modern standards, Paracelsus
    envisioned using pharmaceutical methods for
    treating disease and something like inoculation
    for preventing it.

Scientific Development From 1543 to 1789
  • 1543 Nicolas Copernicus (1473-1543) publishes De
    Revolutionibus Orbium Coelestium, which argues
    that the Sun is the center of the Solar System.
  • 1543 Andrea Vesalius (1514-1564) publishes
    Concerning the Structure of the Human Body, the
    first modern anatomical text.
  • 1600 William Gilbert (1540-1603) publishes
    Concerning the Magnet.
  • 1605 Francis Bacon (1561-1626) publishes
    Advancement of Learning.
  • 1609 Astronomia Nova is published by Johannes
    Kepler (1571-1630), in which he presented his
    first two Laws of Planetary Motion.
  • 1610 Galileo Galilei (1564-1642) publishes
    Sidereal Messenger, describing his observations
    using the telescope.
  • 1619 Kepler publishes his Third Law in Harmonia

Scientific Development From 1543 to 1789
1628 William Harvey (1578-1657) publishes On
the Motion of the Heart and Blood in Animals, in
which he proves that the heart circulates blood
throughout the body. 1632 Galileo publishes
Concerning the Two Chief World Systems, in which
he compares the Copernican and Ptolemaic solar
systems. 1637 Rene Descartes publishes his
Discourse on Method, in which he lays the
foundation for modern philosophy. 1644-9
Pierre Gassendi (1592-1655), in a series of
works, revives the traditions of Epicureanism and
Skepticism. 1660 Robert Boyle (1627-1691)
publishes New Experiments Physico-Mechanical
Touching the Spring of the Air, in which he
states his laws of gases. 1662 The Royal
Society of London is founded.

Scientific Development From 1543 to 1789
  • 1666 The French Academy of Science is founded.
  • 1677 Anton von Leeuwenhoek (1632-1723), using a
    microscope, discovers male spermatoza.
  • 1678 Christian Huygens (1629-1695) proposes the
    wave theory of light.
  • 1687 Isaac Newton (1642-1727) publishes his
    Principia Mathematica.
  • 1704 Isaac Newton publishes his Optics.
  • 1735 Carolus Linnaeus publishes his Systema
    Naturae, which establishes the science of
  • 1789 Antoine Lavoisier publishes his treatise
    on chemistry, laying the foundation for the
    modern theory of chemical elements.

Copernicus b. 1473 Poland
  • Polish astronomer who developed the theory that
    the earth is a moving planet. In Copernicus's
    time, most astronomers accepted the theory the
    Greek astronomer Ptolemy had formulated nearly
    1,400 years earlier.
  • Some astronomers before Ptolemy had suggested
    that the earth did in fact move. Copernicus
    decided that the simplest and most systematic
    explanation of heavenly motion required that
    every planet, including the earth, revolve around
    the sun. The earth also had to spin around its
    axis once every day. The earth's motion affects
    what people see in the heavens, so real motions
    must be separated from apparent ones.
  • Copernicus skillfully applied this idea in his
    masterpiece, On the Revolutions of the Heavenly
    Spheres (1543). In this book, he demonstrated how
    the earth's motion could be used to explain the
    movements of other heavenly bodies. Copernicus
    could not prove his theory, but his explanation
    of heavenly motion was mathematically strong and
    was less complicated than Ptolemy's theory. By
    the early 1600's, such astronomers as Galileo in
    Italy and Johannes Kepler in Germany began to
    develop the physics that would prove Copernicus'
    theory correct.

Nikolai Copernicus
  • Wrote
  • On the Revolution of Celestial Orbs
  • His philosophy of Science
  • True assumptions must save the appearances.

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Tycho Brahe b. 1546
  • Danish astronomer. Brahe developed a systematic
    approach for observing the planets and stars. He
    stressed the importance of making such
    observations on a regular basis. The telescope
    had not yet been invented, and so Brahe used his
    eyesight and such instruments as astrolabes and
    quadrants to estimate the positions of celestial
    objects. His observations were far more precise
    than those of any earlier astronomer.
  • Brahe's observations of planetary motion revealed
    that the tables then in use to predict the
    positions of the planets were inaccurate. His
    sighting of a supernova (type of exploding star)
    in 1572 helped disprove the ancient idea that no
    change could occur in the heavens beyond the
    orbit of the moon.
  • Like many astronomers of his time, Brahe refused
    to accept the Copernican theory of the solar
    system. According to this theory, the earth and
    the other planets move around the sun. Brahe
    reasoned that if the earth revolved around the
    sun, he should have been able to measure changes
    in the positions of the stars resulting from the
    earth's movement. He did not realize that such
    changes were too small for his instruments to
    detect. However, Brahe's observational data later
    enabled Johannes Kepler, a German astronomer and
    mathematician, to confirm the Copernican theory.
  • Brahe was born in Knudstrup (then a Danish city
    but now in Sweden), near Malmo. As a member of
    the nobility, he attended universities in
    Denmark, Germany, and Switzerland. Brahe built an
    elaborate observatory on the island of Hven (now
    called Ven), where he made many of his

Tycho Brahe b. 1546
  • Danish astronomer. Brahe developed a systematic
    approach for observing the planets and stars. He
    stressed the importance of making such
    observations on a regular basis. The telescope
    had not yet been invented, and so Brahe used his
    eyesight and such instruments as astrolabes and
    quadrants to estimate the positions of celestial
    objects. His observations were far more precise
    than those of any earlier astronomer.
  • Brahe's observations of planetary motion revealed
    that the tables then in use to predict the
    positions of the planets were inaccurate. His
    sighting of a supernova (type of exploding star)
    in 1572 helped disprove the ancient idea that no
    change could occur in the heavens beyond the
    orbit of the moon.

Tycho Brahe (1546-1601)
Johannes Kepler b. 1571
  • Discovered three laws of planetary motion.
  • Newton later used Kepler's three laws to arrive
    at the principle of universal gravitation
  • Kepler's laws are
  • (1) Every planet follows an oval-shaped path, or
    orbit, around the sun, called an ellipse. The sun
    is located at one focus of the elliptical orbit.
  • (2) An imaginary line from the center of the sun
    to the center of a planet sweeps out the same
    area in a given time. This means that planets
    move faster when they are closer to the sun.
  • (3) The time taken by a planet to make one
    complete trip around the sun is its period. The
    squares of the periods of two planets are
    proportional to the cubes of their mean distances
    from the sun.
  • Kepler formed an association with Tycho Brahe,
    which shaped the rest of his life.
  • His most significant discoveries trying to find
    an orbit to fit all Brahe's observations of the
    planet Mars. Earlier astronomers thought a
    planet's orbit was a circle or a combination of
    circles. However, Kepler could not find a
    circular arrangement to agree with Brahe's
    observations. He realized that the orbit could
    not be circular and resorted to an ellipse in his
    calculations. The ellipse worked, and Kepler
    destroyed a belief that was more than 2,000 years
  • Kepler was the first astronomer to openly uphold
    the theories of the Polish astronomer Nicolaus

Johannes Kepler b. 1571
  • Kepler formed an association with Tycho Brahe,
    which shaped the rest of his life.
  • His most significant discoveries trying to find
    an orbit to fit all Brahe's observations of the
    planet Mars. Earlier astronomers thought a
    planet's orbit was a circle or a combination of
    circles. However, Kepler could not find a
    circular arrangement to agree with Brahe's
    observations. He realized that the orbit could
    not be circular and resorted to an ellipse in his
    calculations. The ellipse worked, and Kepler
    destroyed a belief that was more than 2,000 years
  • Kepler was the first astronomer to openly uphold
    the theories of the Polish astronomer Nicolaus

Johannes Kepler b. 1571
  • The orbits of the planets are ellipses, with the
    Sun at one focus of the ellipse.

Johannes Kepler b. 1571
  • The line joining the planet to the Sun sweeps out
    equal areas in equal times as the planet travels
    around the el

Johannes Kepler b. 1571
  • The ratio of the squares of the revolutionary
    periods for two planets is equal to the ratio of
    the cubes of their semi-major axes
  • T2/R3 constant for all planets

Gilbert, William (1540-1603),
  • Gilbert, William (1540-1603), an English doctor
    and scientist, was the first person to use the
    word electricity. He has been called the "Galileo
    of Magnetism" because of his celebrated book De
    Magnete, which he published in 1600. It was
    concerned with the properties of magnetism, with
    electricity, and with the use of compasses in
  • Gilbert's most important discoveries in the field
    of magnetism were the laws of attraction and
    repulsion, magnetic dip, and the properties of
    loadstones. Gilbert based his findings on
    observation and practical experiments. This
    practice differed greatly from that of most of
    the scientists of his time, who developed only
    abstract theories, unsupported by experiments.
  • Gilbert was born in Colchester, in Essex,
    England, and was educated at St. John's College,
    Cambridge. He was physician to Queen Elizabeth I
    and attended her during her last illness. Gilbert
    died on Nov. 30, 1603.

William Harvey (1578-1657)
  • An English physician who became famous for his
    discovery of how blood circulates in mammals,
    including human beings. He described his
    discovery in An Anatomical Study of the Motion of
    the Heart and of the Blood in Animals (1628).
    This work became the basis for all modern
    research on the heart and blood vessels.

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Galileo Galilei
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  • The Italian physicist Galileo discovered
    the laws of the pendulum. He noticed that a
    hanging lamp would swing with an almost constant
    period, whether the arc was large or small. He
    believed that a pendulum could regulate the
    movements of clocks. The Dutch scientist
    Christiaan Huygens patented the first pendulum
    clock in 1657. Galileo's observations are still
    correct as long as the pendulum's swing is small.
    But modern measuring instruments have shown that
    the period of a pendulum increases when it has a
    large swing.

  • The Simple Pendulum
  • If a pendulum of mass m attached to a string of
    length L is displaced by an angle from the
    vertical, it experiences a net restoring force
    due to gravity
  • In this small angle approximation, the amplitude
    of the pendulum has no effect on the period. This
    is what makes pendulums such good time keepers.
    As they inevitably lose energy due to frictional
    forces, their amplitude decreases, but the period
    remains constant.

Astronomy and Kinematics
  • Galileo also pursued research on
    motion-especially the motion of freely falling
    bodies. The problem, as he saw it, was that the
    Aristotelian theory of motion, which referred all
    motion to a stationary earth at the center of the
    universe, made it impossible to believe the earth
    actually moves. Galileo went to work to develop a
    theory of motion consistent with a moving earth.

Astronomy and Kinematics
  • In 1610 Galileo made observations of sunspots and
    of Venus, noting that the planet progresses
    through phases similar to those of the moon. This
    fact confirmed his doubts about Ptolemaic
    astronomy and deepened his conviction of the
    truth of Copernicus' theory that the earth and
    planets revolve around the sun. Publication of
    these findings, starting in 1610, brought him
    wide renown.

Astronomy and Kinematics
  • Among the most important results of this search
    were the law of the pendulum and the law of
    freely falling bodies. Galileo observed that
    pendulums of equal length swing at the same rate
    whether their arcs are large or small. Modern
    measuring instruments show that the rate is
    actually somewhat greater if the arc is large.
    Galileo's law of falling bodies states that all
    objects fall at the same speed, regardless of
    their mass and that, as they fall, the speed of
    their descent increases uniformly.

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GALILEO GALILEI 1610 Published The Starry
Messenger The Bible was written to show us how
to go to heaven, not how the heavens go In
discussions of physical problems we ought to
begin not from the authority of scriptural
passages, but from the sense-experiences and
necessary demonstrations. For the Holy Bible
and the phenomena of nature proceed alike from
the divine Word, the former as the dictate of the
Holy Spirit and the latter as the observant
executor of Gods commands.
GALILEO (cont.) To ban Copernicus now that his
doctrine is daily reinforced by many new
observations would seem in my judgment to be a
contravention of truth, and an attempt to hide
and supress her the more as she revealed herself
the more clearly and plainlyAnd to prohibit the
whole science would be but to censure a hundred
passages of holy scripture which teaches us that
the glory and greatness of Almighty God are
marvelously discerned in all his works and
divinely read in the open book of heaven. 1632
Dialogue of the two Chief World Systems
Descartes 1596 - 1650
  • French philosopher, mathematician, and scientist.
    He is often called the father of modern
    philosophy. Descartes invented analytic geometry
    and developed a detailed account of the physical
    universe in terms of matter and motion. He was a
    pioneer in the attempt to formulate simple,
    universal laws of motion that govern all physical

Rene Descartes
  • Rene Descartes was one of the founders of modern
    philosophy. In this painting, Descartes conducts
    a scientific experiment for Queen Christina of
    Sweden shortly before his death in 1650.
  • Detail of Rene Descartes Conducts a Demonstration
    Before Queen Christina of Sweden (about 1700) oil
    on canvas by Dumesnil (The Art Archive)

Bacon, Francis (1561-1626)
  • English philosopher, essayist, jurist, and
    statesman. He was one of the earliest and most
    influential supporters of empirical
    (experimental) science and helped develop the
    scientific method of solving problems.
  • Bacon believed all previous claims to knowledge,
    particularly of medieval science, were doubtful
    because they were based on poor logic. He
    believed the mind makes hasty generalizations,
    which prevent the attainment of knowledge. But he
    also believed that the mind could discover truths
    that would enable humanity to conquer disease,
    poverty, and war by gaining power over nature. To
    discover truths, the human mind must rid itself
    of four prejudices. Bacon called these prejudices
    Idols of the Mind.
  • Bacon believed the mind could attain truth if it
    followed the inductive method of investigation.
    He developed four steps of doing so (1) listing
    all known cases in which a phenomenon occurs (2)
    listing similar cases where the phenomenon does
    not occur (3) listing the cases in which the
    phenomenon occurs in differing degrees and (4)
    examination of the three lists. These steps would
    lead to the cause of a phenomenon.
  • Bacon suggested the use of preliminary hypotheses
    (assumptions) to aid scientific investigation.
    His treatment of hypothesis is still a subject of
    study. Bacon also wrote an unfinished romance
    called New Atlantis (published in 1627, after his
    death). The book describes an imaginary island
    where the inhabitants dedicate themselves to the
    study of science.

Robert Boyle (1627-1691)
  • an Irish scientist, is considered the founder of
    modern chemistry. He helped establish the
    experimental method in chemistry and physics.
  • Boyle is best known for his experiments on gases
    that led to the formulation of Boyle's law (see
    GAS (Gas laws)). This law says the volume of a
    gas at constant temperature varies inversely to
    the pressure applied to the gas. Boyle also
    helped improve the air pump, and with it he
    investigated the nature of vacuums.
  • Boyle introduced many new methods for determining
    the identity and chemical composition of
    substances. He disproved the theory that air,
    earth, fire, and water were the basic elements of
    all matter. Boyle argued that all basic physical
    properties were due to the motion of atoms, which
    he called "corpuscles."
  • Boyle lived in England for most of his life. He
    was a founding member of the Royal Society of
    London, one of the world's foremost scientific
    organizations. Boyle described his experiments in
    many books. He was born at Lismore Castle,

Robert Boyle (1627-1691)
ROBERT BOYLE Wrote The Excellence of Theology
or The Preeminence of the Study of Divinity Above
That of Natural Philosophy Wrote The Skeptical
Chymist Scientist should Set themselves
diligently to make experiments and collect
observations, without being overtoward to
establish principles and axioms. Theories are
never final, but should be thought of as the
best we have, but capable of improvement.
Boyle (cont.)
  • We assent to experience, even when its
    information seems contrary to reason.
  • Objects have color by virtue of a certain
    disposition of the superficial particles which
    are capable of refracting and reflecting light
    (ie. color is a secondary property)

Robert Hooke
  • The Science of Nature has been already too long
    made only a work of the brain and the fancy. It
    is now high time that it should return to the
    plainness and soundness of observations on
    material and obvious things.

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Sir Isaac Newton, 1642-1272 Mathematician,
Philosopher, Alchemist, Deist and Scientist
Isaac Newton 1642 - 1727
  • Proposed three laws of mechanics
  • 1. Inertia - A body continues to move in a
    straight line unless acted upon by a force
  • 2. F ma Acceleration is proportional
    to the applied force. As long as the force is
    applied the velocity increases.
  • 3. For every action there is a reaction
  • Explained motion of planets and moon
  • Proposed law of universal gravitation
  • Explained tides
  • Assumed laws on Earth were same as in the heavens
  • Discovered light composed of different color
  • Invented reflector telescope

SIR ISAAC NEWTON Whence is it that nature does
nothing in vain and whence arises all that order
and beauty which we see in the world? The best
and safest method of philosophizing seems to be,
first to inquire diligently into the properties
of things, and to establish those properties by
experiences and then to proceed more slowly to
hypothesis for the explanation of them. For the
hypothesis should be employed only in explaining
the properties of things, but should not be
assumed in determining them. 1687 Published
Newtons Laws of Motion
  • 1 Objects with no net external force applied to
    them will move with a constant velocity
  • 2 The acceleration of an object is directly
    proportional to the net force applied to the
    object and inversely proportional to its mass.
  • 3 Whenever an object exerts a force on a
    second object, the second object exerts an equal
    but opposite force on the first.

Newtons Rules of Reasoning
  • Use no more hypothesis than needed a restatement
    of Ockhams Razor
  • Apply same cause to same effect
  • Properties on earth are same as properties (laws)
    in other parts of universe
  • Offer hypotheses supported only by experiment
  • we are to look upon propositions inferred by
    general induction from phenomena as accurately or
    very nearly true, not withstanding any contrary
    hypothesis that may be imagined till such time as
    other phenomena occur by which they may either
    be made more accurate or liable to exception

Corpuscular Theory of Light (1704)
  • Isaac Newton proposed that light consists of a
    stream of small particles, because it
  • travels in straight lines at great speeds
  • is reflected from mirrors in a predictable way

Wave Theory of Light
  • Hooke, Grimaldi and Huygens (idea of a wave
  • Thomas Young (1802) showed that light is a wave,
    because it
  • undergoes diffraction and interference (Youngs
    double-slit experiment)

Thomas Young (1773-1829)
  • Position x
  • Mass m
  • Momentum p mv

  • Wavelength l
  • Amplitude A
  • Frequency f
  • number of cycles per second (Hertz)

f c / l
Waves versus Particles
  • A particle is localized in space, and has
    discrete physical properties such as mass
  • A wave is inherently spread out over many
    wave-lengths in space, and could have amplitudes
    in a continuous range
  • Waves superpose and pass through each other,
    while particles collide and bounce off each other

Interference Fringes on a Screen
Joseph Priestley 1733-1804
Phlogiston Theory
Henry Cavendish 1731-1810
Experiments on Air 1766 Measured G the universal
gravitational constant
Antoine Lavoisier 1743 - 1794
  • French chemist who, through a conscious
    revolution, became the father of modern
    chemistry. He won a prize on lighting the
    streets of Paris, and designed a new method for
    preparing saltpeter. He also married a young,
    beautiful 13-year-old girl named Marie-Anne, who
    translated from English for him and illustrated
    his books. He burnt phosphorus and sulfur in air,
    and proved that the products weighed more than he
    original. Nevertheless, the weight gained was
    lost from the air. Thus he established the Law of
    Conservation of Mass.

Antoine LaVossierre I have tried to arrive at
truth by linking up facts to suppress as much as
possible the use of deductive reasoning, which
is so often an unreliable instrument which
deceives us, in order to follow as much as
possible the torch of observation and experiment.
John Dalton 1766-1844
John Daltons Atomic Theory (1804)
  • Elements are composed of identical atoms
  • The atoms of an element cannot be changed into
    atoms of another element.
  • Compounds form when the atoms of two or more
    elements combine in a definite (exact) integer
    ration. (in other words, compounds have a formula)

Michael Faraday, b. Sept. 22, 1791 d. Aug. 25,
  • The English chemist and physicist Michael
    Faraday, b. Sept. 22, 1791, d. Aug. 25, 1867, is
    known for his pioneering experiments in
    electricity and magnetism. Many consider him the
    greatest experimentalist who ever lived. Several
    concepts that he derived directly from
    experiments, such as lines of magnetic force,
    have become common ideas in modern physics.

Michelson and Morley
  • During the 1800's, physicists tried
    unsuccessfully to measure the speed of the earth
    relative to the ether. According to classical
    physics, the ether was motionless. In the early
    1880's, Hendrik A. Lorentz, a Dutch physicist,
    explained the failure of these experiments by
    assuming that the ether was partially dragged
    along as the earth moved through it. Two American
    physicists, Albert A. Michelson and Edward W.
    Morley, developed an instrument that made far
    more precise measurements than earlier devices.
    Their experiments helped destroy the ether
    theory. In 1887, Michelson and Morley
    demonstrated that the earth's movement around the
    sun had no effect on the speed of light. Their
    finding could be understood only by assuming that
    the ether near the surface of the earth moved at
    the same speed as the earth. However, this
    assumption contradicted the results of many other

Maxwell, James Clerk (1831-1879)
  • Scottish scientist, one of the greatest
    mathematicians and physicists of the 1800's is
    best known for his research on electricity and
    magnetism and for his kinetic theory of gases.
    This theory explains the properties of a gas in
    terms of the behavior of its molecules. Maxwell
    also investigated color vision, elasticity,
    optics, Saturn's rings, and thermodynamics, a
    branch of physics that deals with heat and work.
  • Maxwell based his work on electricity and
    magnetism on the discoveries of the English
    physicist Michael Faraday. In 1864, Maxwell
    combined his ideas with those of Faraday and
    certain other scientists and formed a
    mathematical theory that describes the
    relationship between electric and magnetic
    fields. Both these fields exert forces on
    electrically charged objects. Maxwell showed that
    waves in combined electric and magnetic fields,
    called electromagnetic waves, travel at the speed
    of light. In fact, Maxwell argued that light
    itself consists of electromagnetic waves. In the
    late 1880's, the German physicist Heinrich R.
    Hertz conducted experiments that confirmed
    Maxwell's theory.
  • Maxwell's equations indicate that light moves at
    a particular speed, represented by the letter c.
    The value of c is now known to be 186,282 miles
    (299,792 kilometers) per second. Maxwell assumed
    that c was the speed of light relative to the
    ether. According to this assumption, light would
    travel faster or slower than c in an inertial
    frame moving relative to the ether.

  • James Clerk Maxwell was one of the greatest
    scientists who have ever lived. To him we owe the
    most significant discovery of our age - the
    theory of electromagnetism. He is rightly
    acclaimed as the father of modern physics. He
    also made fundamental contributions to
    mathematics, astronomy and engineering.

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Albert Einstein (1879-1955),
  • Was one of the greatest scientists of all time.
    He is best known for his theory of relativity,
    which he first advanced when he was only 26. He
    also made many other contributions to science.
  • Relativity. Einstein's relativity theory
    revolutionized scientific thought with new
    conceptions of time, space, mass, motion, and
    gravitation. He treated matter and energy as
    exchangeable, not distinct. In so doing, he laid
    the basis for controlling the release of energy
    from the atom.
  • Thus, Einstein was one of the fathers of the
    nuclear age. Einstein's famous equation, E equals
    m times c-squared (energy equals mass times the
    velocity of light squared), became a foundation
    stone in the development of nuclear energy.
    Einstein developed his theory through deep
    philosophical thought and through complex
    mathematical reasoning. The great scientist was
    once reported to have said that only a dozen
    people in the world could understand his theory.
    However, Einstein always denied this report.

Principles of Relativity
  • Einstein introduced a new principle, the special
    principle of relativity. This principle has two
    parts (1) There is no ether, and the speed of
    light is the same for all observers, whatever
    their relative motion. (2) The laws of nature are
    the same in all inertial frames, where the laws
    are understood to include those described by

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