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Physics

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Title: Physics


1
Physics
2
Etymology of the word PhysicsPhysics comes
from the Greek word F?s???, title of one of
Aristotles book it is an adjective meaning
everything related to nature (F?s??.) Thus,
any type of motion as the solar system evolution,
all we can investigate with our senses that is
related to nature belongs to the field of
Physics.In antiquity, sciences
appeared and were prematurely systematized not
strictly separated, as in modern times, but they
all belonged to the global science of
philosophy today, of course, sciences are
fully separated and specialized, while philosophy
has been reduced to a discipline of the
humanitarian sciences.
3
Archeological findings reveal that nature and
celestial motions had attained the interest of
different cultures and nations of the ancient
times. Assyrians (the ancient people of Syria
nowadays), Babylonians (the inhabitants of
Mesopotamia, Iran-Iraq nowadays) and ancient
Egyptians had advanced knowledge of astronomy,
forming very accurate calendarsOf course, that
was not due to scientific research and
theoretical interest, but to necessity for their
land cultivation they had observed specific
phenomena as for example, the rise of the waters
of the Nile which occurred periodically every
year and that initiated their knowledge. The
indigenous populations of America, Mayas and
Aztecs, also had important astronomical knowledge
as demonstrated by their monuments and very
accurate (even for our time) calendars (of course
their culture reached its peak almost two
millenniums after, around 600 AD to 1000
AD!)The first to present a systematized
scientific thought were ancient Greeks, who
passed from the everyday problems to theoretical
research and, thus, gave birth to sciences.
Interestingly, many modern theories converge or
even are inspired for future research by theories
presented by Greek philosophers the Big Bang
theory itself is believed to have many common
points with Heraclitus theory of the Big Fire
Sphere Sfa???? from which everything initiates
and to which everything eventually returns at the
end of Times. There is a famous quote by
Heraclitus ???ta ?e? ?a? ??d?? µ??e? (English
Everything flows, nothing stands still) Quantum
Physics claim today that even at absolute zero
(0K) quantum-mechanical motion disturbances
appear, confirming Heraclitus 2 and a half
milleniums after!
4
(a) Leucippus or Leukippos (Greek ?e???pp??,
first half of 5th century BC) There are no
existing writings which we can attribute to
Leucippus, since his writings seem to have been
enfolded into the work of his famous student
Democritus. The most famous among Leucippus' lost
works were titled Megas Diakosmos (The Great
Order of the Universe or The great world-system)
and Peri Nou (On mind).A single fragment of
Leucippus survives Nothing happens at random
(maten), but everything from reason (ek logou)
and by necessity. Leucippus, Diels-Kranz 67
B1(b) his student Democritus, 460-370 B.C.,
Democritus argued the eternity of existing
nature, of void space, and of motion. He
supposed the atoms are originally similar, and
that even the human soul consists of globular
atoms of fire, which impart movement to the
body. and (c) Epicurus, 341-270
B.C. Epicurus adopted the atomism of
Leucippus and Democritus, maintaining that
all objects and eventsincluding human
livesare in reality nothing more than
physical interactions among minute indestructible
particles. His difference was that he
believed there is no necessity Gk. anagkh
anankê about any of this, of
course everything happens purely by chance.
One of the most fundamental theories of the
ancient Greek thought which is also our modern
society point of view about the construction and
evolution of nature and space is the theory of
atomism the philosophical belief (and
experimentally proved nowadays) that everything
is composed entirely of various impenetrable,
indivisible elements called the atoms
(?t?µ??, adjective meaning that it can no
further be divided, cut). Theory expressed by
three philosophers
5
The most important scientific contribution of the
Greeks to modern times was their knowledge and
extensive research on the celestial world Greek
mythology found its place not only on our solar
system, with the name of the sun and the six
known planets of antiquity, but also to all the
constellations of the northern hemisphere and
partially the southern, giving names which still
hold in our times. That research was the
outcome of their need for navigation (even
during night), thus rendering constellations
their secure compass over night. Moreover,
their moon-based 12 month calendar (even though
the names of the months are completely changed
and their duration changed slightly) and seven
days weekly calendar was adopted by the Romans,
the Christians and was inherited to our modern
societies.
Celestial Sphere
Constellation of Orion
Map of the Mediterranean Sea
6
Names of the 7 daysFrench
English planet/God(ess) Lundi
(lune moon) Monday (moon)
Moon(Diane) Mardi (mars)
Tuesday (G.Eq.) Mars/Tyr,TewMercredi
(mercure)
Wednesday (G.Eq.) Mercury/Woden
Wodnes Jeudi (jeus)
Thursday (G.Eq.)
Jupiter/ThorVandredi (venus)
Friday (G.Eq.)
Venus/Freya-Frige Samedi (Christian)
Saturday (Saturn)
SaturnDimanche (Christian)
Sunday (Sun)
SunInteresting enough, Greeks no longer use
these names! (They name days after the
Bible)G.Eq. German Equivalent
7
Except from the great contribution of Aristotle,
Plato and the other Greek philosophers, an
important figure was the astronomer Aristarchus
of Samos, (310-230 B.C.) who firstly introduced
the idea of the heliocentric solar system at 231
B.C., i.e. that the center of our solar system
was not the earth as believed but the sun. To
arrive at his conclusion he proved that the
bigger of the three bodies, the sun the earth and
the moon, is the sun and by far, and therefore
the sun is at the center of the solar system.
One last, but not least, reference should be made
for the so believed most important and
influential of all ancient Greek astronomers,
Hipparchus of Rhodes, (190 120 B.C.), the
person who made the most important contribution
before that of Copernicus in the early 17th
century A.D. His approach to science ranks him
far above other ancient astronomers. It was
based on data from accurate observations, and is
essentially modern in that he collected his data
and then formed his theories to fit the observed
facts. Most telling regarding his understanding
of the scientific method is the fact that he
proposed a theory of the motion of the sun and
the moon yet he was not prepared to propose such
a theory for the planets. He realized that his
data was not sufficiently good or sufficiently
plentiful to allow him to base a theory on it.
However, he made observations to help his
successors to develop such a theory. Most of his
work was incorporated in the work of Ptolemy.
8
Claudius Ptolemaeus, Greek??a?d??? ?t??eµa???,
English Ptolemy (90-168) Greek-speaking
geographer, astronomer, and astrologer who lived
in the Hellenistic culture of Roman Egypt.
Ptolemy was the author of several scientific
treatises, three of which have been of continuing
importance to later Islamic and European science.
The first is the astronomical treatise that is
now known as the Almagest (in Greek ? µe????
S??ta???, "The Great Treatise"). The second is
the Geography, which is a thorough discussion of
the geographic knowledge of the Greco-Roman
world. The third is an astrological treatise
known as the Tetrabiblos ("Four books").
Astronomy In the Almagest, one of the most
influential books of classical antiquity, Ptolemy
relied mainly on the work of Hipparchus of three
centuries earlier. It was preserved, like most
of Classical Greek science, in Arabic manuscripts
(hence its name) and only made available in Latin
translation in the 12th century. Ptolemy
formulated a geocentric model that was widely
accepted until the heliocentric solar system of
Copernicus. Likewise his computational methods
were of sufficient accuracy to satisfy the needs
of astronomers and navigators, until the time of
the great explorations. They were also adopted
in the Arab world and in India. The Almagest
also contains a star catalogue, which is probably
an updated version of a catalogue created by
Hipparchus. Its list of forty-eight
constellations is ancestral to the modern system
of constellations, but unlike the modern system
they did not cover parts of the southern
hemisphere (only the sky Ptolemy could see). The
Almagest is also known as the Great Syntaxis of
Astronomy.
9
Other worksIn his Optics, a work which survives
only in a poor Arabic translation, he writes
about properties of light, including reflection,
refraction and colour. The work is a significant
part of the early history of optics. His other
works include Planetary Hypothesis,
Planisphaerium and Analemma.
Ptolemy's theoremIf the quadrilateral inscribed
in a circle is given by its four vertices A, B,
C, and D in order, then the theorem states
that where the overbar denotes the lengths of
the line segments between the named vertices."If
a quadrilateral is inscribed in a circle then the
sum of the products of its two pairs of opposite
sides is the product of its diagonals".The
converse of Ptolemy's theorem is also true (In a
quadrilateral, if the sum of the products of its
two pairs of opposite sides is the product of its
diagonal, then it can be inscribed in a circle).
Canon of Kings The Canon of Kings was a dated
list of kings used by ancient astronomers as a
convenient means to date astronomical phenomena,
such as eclipses. The Canon was preserved by the
astronomer Claudius Ptolemy. It is one of the
most important bases for our knowledge of ancient
chronology. The Canon derives originally from
Babylonian sources. Canon Contents(1)
Babylonian Kings, 747-539 BC, (2) Persian Kings,
538-332 BC , (3) Macedonian Kings, 331-305 BC (4)
Ptolemies of Egypt, 304-30 BC , (5) Roman
Emperors, 29 BC-AD 160
10
Ptolemy was the last of the circle of ancient
scientists. After his work science faced
retrogression and decline the Roman Empire was
not particularly interested in scientific work
(as in the Hellenistic period), the famous
Library of Alexandria was burnt, destroying more
than 90 of the written knowledge of Antiquity,
and the religion of Christianity appeared as a
revolution and resistance to the Roman empire,
religion and everything related to the ancient
world, including all scientific advancements and
forbidding any research or doubt over the
absolute will of the Lord. During the Middle
Age, the Dark Ages in Western Europe, the only
light of wisdom were Byzantium -The Eastern Roman
Empire- that preserved the rest of the books,
continuing the work and philosophy of the Academy
of Plato up to the 7th century A.D., and the
Arabs The liberating form of the religion of
Islam at that time gave space for scientific
research and evolution at these lands once more.
An important contribution of the Arabs are the so
called Arabic numbers, the ones we use
nowadays.The numbers were developed in India by
the Hindus around 400 BCE, and the Arabs adopted
and relayed this system to the West. For
almost 1000 years Aristotle and Ptolemy were the
absolute and undoubted truth of the Western
populations, with their work known mainly through
Arabic translations. The destruction of
Byzantium in the middle of the 15th century A.D.,
forced Greeks from Constantinople and elsewhere
in Greece to immigrate towards Italy (Florence,
Venice, etc.), bringing books of the ancient
Greek philosophers and rendering the ancient
philosophers work known to the Western countries,
thus initiating (in combination with the
invention of press) the beginning of the period
known as the Renaissance. People like Galileo
Galilei and others started doubting the absolute
truth of the religion and the Church, and gave
birth to what we call nowadays scientific
research and enterprise. In the following a
list of the different chronological steps in
scientific thought and the main figures who
initiated them, and who led humanity from the
Dark Ages to our modern way of thinking, is
presented.
11
Celestial Dynamics, Terrestrial
MechanicsCopernicus (De revolutionibus orbioum
coelestium On the revolutions of the heavenly
spheres) (1543)Galileo Galilei (the
Dialogue) (1564-1642)Kepler Johannes
(1571-1630) (Mysterium Cosmographicum
Cosmographic Mystery)BaconThe Mechanical
PhilosophyVan Helmont (influenced by
Paracelsus)DescartesThe Mechanical
SciencePascalHuygens (essay on light)The
Mechanical ChemistryParacelsusNicolas
LemeryRobert BoyleOrganization of the
Scientific EnterpriseRobert Boyle (definition
of the experimental method)DescarteThe Science
of MechanicsDescarteNewtonian
DynamicsGalileo GalileiNewton
12
Nicolaus Copernicus (February 19, 1473 May
24, 1543) Astronomer who provided the first
modern formulation of a heliocentric
(sun-centered) theory of the solar system in
his epochal book, De revolutionibus orbium
coelestium (On the Revolutions of the Celestial
Spheres). Copernicus was one of the great
polymaths of the Renaissance. Mathematician,
astronomer, jurist, physician, classical scholar,
governor, administrator, diplomat, economist,
and soldier. His formulation of how the sun
rather than the earth is at the center of the
universe is considered one of the most
important scientific hypotheses in history. It
mark the starting point of modern astronomy
and of modern science, encouraging young
astronomers, scientists and scholars to take a
more skeptical attitude toward established
dogma.The Copernican heliocentric
systemCopernicus cited Aristarchus and
Philolaus in an early manuscript of his book
which survives, stating "Philolaus believed in
the mobility of the earth, and some even say that
Aristarchus of Samos was of that opinion."
Inspiration came to Copernicus not from
observation of the planets, but from reading two
authors Hicetas and Plutarch provided an account
of the Pythagoreans Heraclides Ponticus,
Philolaus, and Ecphantes. These philosophers had
proposed a moving earth, which did not, however,
revolve around a central sun.
13
It has been argued that in developing the
mathematics of heliocentrism Copernicus drew on,
the Greek and the Islamic tradition of
mathematics and astronomy.Copernicus' major
theory was published in the book, De
revolutionibus orbium coelestium (On the
Revolutions of the Heavenly Spheres) in the year
of his death, 1543.He held that the Earth is
another planet revolving around the fixed sun
once a year, and turning on its axis once a day.
He arrived at the correct order of the known
planets and explained the precession of the
equinoxes correctly by a slow change in the
position of the Earth's rotational axis. He also
gave a clear account of the cause of the seasons
that the Earth's axis is not perpendicular to the
plane of its orbit. But while Copernicus put the
Sun at the center of the celestial spheres, he
did not put it at the exact center of the
universe, but near it.His model had a large
influence on later scientists such as Galileo and
Johannes Kepler, who adopted, championed and
(especially in Kepler's case) sought to improve
it. The Copernican system can be summarized in
seven propositions, as Copernicus himself
14
The seven parts of Copernicus' theory are1.
There is no one center in the universe 2. The
Earth's center is not the center of the universe
3. The center of the universe is near the sun
4. The distance from the Earth to the sun is
imperceptible compared with the distance to the
stars 5. The rotation of the Earth accounts for
the apparent daily rotation of the stars 6. The
apparent annual cycle of movements of the sun is
caused by the Earth revolving around the sun 7.
The apparent retrograde motion of the planets is
caused by the motion of the Earth, from which one
observes
15
Kepler's lawsKepler inherited from Tycho Brahe,
court mathematician to Emperor Rudolf II, a
wealth of the most accurate raw data ever
collected on the positions of the planets. The
difficulty was to make sense of it. The orbital
motions of the other planets are viewed from the
vantage point of the Earth, which is itself
orbiting the sun. As shown to the graph, this can
cause the other planets to appear to move in
strange loops.
Johannes Kepler (December 27, 1571 November 15,
1630) German mathematician, astronomer,
astrologer, and an early writer of science
fiction stories, a key figure in the scientific
revolution. He is best known for his laws of
planetary motion, based on his works Astronomia
nova, Harmonice Mundi and the textbook Epitome of
Copernican Astronomy.
16
Kepler concentrated on trying to understand the
orbit of Mars, but he had to know the orbit of
the Earth accurately first. So, he used Mars and
the Sun as his baseline, since without knowing
the actual orbit of Mars, he knew that it would
be in the same place in its orbit at times
separated by its orbital period. Thus the orbital
positions of the Earth could be computed, and
from them the orbit of Mars.
He finally arrived at his three laws of planetary
motion Kepler's elliptical orbit law The
planets orbit the sun in elliptical orbits
with the sun at one focus. Kepler's
equal-area law The line connecting a planet to
the sun sweeps out equal areas in equal
amounts of time. Kepler's law of periods
The time required for a planet to orbit the
sun, called its period, is proportional to the
long axis of the ellipse raised to the 3/2
power. The constant of proportionality is the
same for all the planets. He was the first
astronomer to successfully predict a transit of
Venus (for the year 1631). Kepler's laws were the
first clear evidence in favor of the heliocentric
model of the solar system. Isaac Newton
eventually showed that the laws were a
consequence of his laws of motion and law of
universal gravitation.
17
In 1604, Kepler observed a supernova in the
constellation Ophiuchus, the first and only
ever since in the Milky Way. Kepler also made
fundamental investigations into
combinatorics, geometrical optimization, and
natural phenomena such as snowflakes, always
with an emphasis on form and design. He was
also one of the founders of modern optics,
defining for example antiprisms and the
Kepler telescope. In addition, since
he was the first to recognize the non- convex
regular solids (such as the stellated
dodecahedra), they are named Kepler solids
in his honor. Kepler also was in contact with
Wilhelm Schickard, inventor of the first
automatic calculator, whose letters to Kepler
show how to use the machine for calculating
astronomical tables.
Remnant of Kepler's Supernova SN 1604
18
Galileo Galilei (February 15, 1564 January 8,
1642) Italian physicist, astronomer,
astrologer, and philosopher who is closely
associated with the scientific revolution. His
achievements include improvements to the
telescope, a variety of astronomical
observations, the first and second laws of
motion, and effective support for Copernicanism.
He has been referred to as the "father of modern
astronomy," as the "father of modern physics,"
and as the "father of science." Galileo's career
coincided with that of Johannes Kepler.The work
of Galileo is considered to be a significant
break from that of Aristotle.Scientific
methodsIn the pantheon of the scientific
revolution, Galileo Galilei takes a high position
because of his pioneering use of quantitative
experiments with mathematically analyzed results.
There was no tradition of such methods in
European thought at that time. Galileo also
contributed to the separation of science from
philosophy or religion. These are the primary
justifications for his description as the "father
of science".Galileo showed a remarkably modern
appreciation for the proper relationship between
mathematics, theoretical physics, and
experimental physics.
Famous quote Epur si muoveAnd yet it does move
19
For example - He understood the mathematical
parabola, both in terms of conic sections and in
terms of the square-law. - He asserted that the
parabola was the theoretically-ideal trajectory,
in the absence of friction and other
disturbances. - He recognized that his
experimental data would never agree exactly with
any theoretical or mathematical form, because of
the imprecision of measurement, and because of
irreducible friction, et cetera.
Astronomy Galileo first noted an observation of
the moons of Jupiter. This observation upset the
notion of that time that all celestial bodies
must revolve around the Earth. He firstly
discovered Jupiter's four largest satellites
(moons) Io, Europa, Callisto, and Ganymede. He
observed that Venus exhibited a full set of
phases similar to that of the Moon. These
observations of the phases of Venus proved that
it orbited the Sun and lent support to (but did
not prove) the heliocentric model.
20
He was one of the first Europeans to observe
sunspots, which formerly had been attributed
(impossibly) to a transit of Mercury, and he was
also the first to report lunar mountains and
craters, whose existence he deduced from the
patterns of light and shadow on the Moon's
surface. He also observed the Milky Way,
previously believed to be nebulous, and found
it to be a multitude of stars packed so
densely that they appeared to be clouds from
Earth. He also located many other stars too
distant to be visible with the naked eye.
Finally, Galileo observed the
planet Neptune in 1612, but did not
realize that it was a planet and took no
particular notice of it.
21
Galileo
  • At age 19, Galileo discovered the pendulum, the
    basis for later clocks
  • Galileo questioned Aristotelian physics and
    performed many of his own experiments, especially
    with gravity his work on physics summarized in
    De Moto
  • Most optical telescopes used today derive from
    the
  • two types of telescopes developed in the 17th
    century by Galileo and Newton, which amateur and
    professional astronomers use today

22
Physics Galileo's theoretical and experimental
work on the motions of bodies, along with the
largely independent work of Kepler and René
Descartes, was a precursor of the Classical
mechanics developed by Sir Isaac Newton. He was a
pioneer, at least in the European tradition, in
performing rigorous experiments and insisting on
a mathematical description of the laws of
nature. He performed experiments involving
rolling balls down inclined planes, which proved
that falling or rolling objects (rolling is a
slower version of falling, as long as the
distribution of mass in the objects is the same)
are accelerated independently of their mass.
He determined the correct mathematical
law for acceleration the total distance covered,
starting from rest, is proportional to the square
of the time. He also concluded that objects
retain their velocity unless a force often
friction acts upon them, refuting the generally
accepted Aristotelian hypothesis that objects
"naturally" slow down and stop unless a force
acts upon them. Galileo's Principle of Inertia
stated "A body moving on a level surface will
continue in the same direction at constant speed
unless disturbed." This principle was
incorporated into Newton's laws of motion (first
law).
23
He also noted that a pendulum's swings always
take the same amount of time, independently
of the amplitude. c He is lesser
known for being one of the first to
understand sound frequency. He also put
forward the basic principle of relativity, that
the laws of physics are the same in any system
that is moving at a constant speed in a straight
line, regardless of its particular speed or
direction. This principle provided the basic
framework for Newton's laws of motion and is the
infinite speed of light approximation to
Einstein's special theory of relativity. Galile
o's writings - Two New Sciences 1638 Lowys
Elzevir (Louis Elsevier) Leiden (in Italian,
Discorsi e Dimostrazioni Matematiche, intorno a
due nuoue scienze Leida, Appresso gli Elsevirii
1638) - Letters on Sunspots 1613 - The Assayer
(In Italian, Il Saggiatore) 1623 - Dialogue
Concerning the Two Chief World Systems 1632 (in
Italian, Dialogo dei due massimi sistemi del
mondo) - The Starry Messenger 1610 Venice (in
Latin, Sidereus Nuncius) - Letter to Grand
Duchess Christina 1615
24
THE SCIENTIFIC REVOLUTION
NEW DIRECTIONS IN ASTRONOMY PHYSICS
  • GALILEO GALILEI (1564-1642)
  • Constructed first telescope
  • Described motion of bodies on earth

25
Isaac Newton
  • Kepler's Laws were a revolution in regards to
    understanding planetary motion, but there was no
    explanation why they worked
  • That explanation would have to wait until Isaac
    Newton formulated his laws of motion and the
    concept of gravity
  • Newton's discoveries were important because they
    applied to actions on Earth and in space
  • Besides motion and gravity, Newton also developed
    calculus

Newton (1642-1727)
26
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27
Some terms
  • Force the push or pull on an object that in some
    way affects its motion
  • Weight the force which pulls you toward the
    center of the Earth (or any other body)
  • Inertia the tendency of an object to keep moving
    at the same speed and in the same direction
  • Mass basically, the amount of matter an object
    has
  • The difference between speed and velocity
  • These two words have become identical in common
    language, but in physics, they mean two different
    things
  • Speed is just magnitude of something moving (25
    km/hr)
  • Velocity is both the magnitude and direction of
    motion (35 km/hr to the NE)

28
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29
Newton's First Law
  • Newton's first law states An object at rest will
    remain at rest, an object in uniform motion will
    stay in motion - UNLESS acted upon by an outside
    force
  • This is why you should always wear a seat belt!

Outside Force
30
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31
Newton's Second Law
  • Acceleration is created whenever there is a
    change in velocity
  • Remember, this can mean a change in magnitude
    AND/OR direction
  • Newton's Second Law states When a force acts on
    a body, the resulting acceleration is equal to
    the force divided by the object's mass
  • Notice how this equation works
  • The bigger the force, the larger the acceleration
  • The smaller the mass, the larger the acceleration

or
32
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33
Newton's Third Law
  • Newton's Third Law states For every action,
    there is an equal and opposite reaction
  • Simply put, if body A exerts a force on body B,
    body B will react with a force that is equal in
    magnitude but opposite direction
  • This will be important in astronomy in terms of
    gravity
  • The Sun pulls on the Earth and the Earth pulls on
    the Sun

34
Isaac Newton (1642-1727)
  • Possibly the greatest scientist who ever lived -
    born on the day Galileo died
  • math/physics/astronomy
  • author of Principia Mathematica in 1687
  • bringing together Galileos discoveries about
    motion on Earth and Keplers discoveries in the
    heavens
  • to do so he had to develop calculus
  • explained heavenly motion that was tied to
    observed motion on Earth.

35
Isaac Newton
  • Bodies move in straight lines unless impeded
    (inertia)
  • Every action has an equal and opposite action
  • every body attracts every other body with a
    force proportional to the distance between
  • Provided a synthesis superior to Aristotle
  • notion of inertia - only have to explain change
  • Three Laws of Motion

Nature and natures laws lay hid in night God
said, Let Newton be. and all was light
- Pope.
36
  • Isaac Newton (1643 - 1727)
  • Wrote Principia Methematica which contained
    mathematical
  • Descriptions of how the world works (up to the
    speed of light, as
  • Einstein later proves)

Law 1 Every object continues in its state of
rest or of uniform motion in a straight line,
unless it is compelled to change that state by
forces impressed upon it.   Law 2 The
acceleration of an object is directly
proportional to the net force acting on the
object, is in the direction of the net force,
and is inversely proportional to the mass of the
object.   Law 3 Whenever one object exerts a
force on a second object, the second object
exerts an equal and opposite force on the first.

37
Isaac Newton
Newton solved the premier scientific problem of
his time --- to explain the motion of the planets.
To explain the motion of the planets, Newton
developed three ideas
  1. The laws of motion
  2. The theory of universal gravitation
  3. Calculus, a new branch of mathematics

If I have been able to see farther than others
it is because I stood on the shoulders of
giants. --- Newtons letter to Robert
Hooke, perhaps referring to Galileo and Kepler
38
Isaac Newton
  • Mathematical theories explained the observed
    motions of the planets.
  • Considered the greatest scientific genius until
    Einstein.
  • 1684-wrote his major work, Mathematical
    Principles of Natural Philosophy
  • Theory of gravitation.
  • Planets bound to the sun by gravitation
  • Basic force of gravitation and
  • proved that it explained the motions of the
    planets.

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Newtons Beliefs
  • 1665 Newton developed calculus
  • 1664-1666 Discovered that light is made up of
    different colors by passing sunlight through a
    prism
  • 1666 Began to develop the theory of gravity
  • 1687 Wrote a book on gravity and the laws that
    make objects move---Principia

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Newton and the Apple - Gravity
  • After formulating his three laws of motion,
    Newton realized that there must be some force
    governing the motion of the planets around the
    Sun
  • Amazingly, Newton was able to connect the motion
    of the planets to motions here on Earth through
    gravity
  • Gravity is the attractive force two objects place
    upon one another

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The Gravitational Force
  • G is the gravitational constant
  • G 6.67 x 10-11 N m2/kg2
  • m1 and m2 are the masses of the two bodies in
    question
  • r is the distance between the two bodies

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Gravity - Examples
  • Weight is the force you feel due to the
    gravitational force between your body and the
    Earth
  • We can calculate this force since we know all the
    variables

1 Newton is approximately 0.22 pounds
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Gravity - Examples
  • What if we do the same calculation for a person
    standing on the Moon?
  • All we have to do is replace the Earth's mass and
    radius with the Moon's

1 Newton is approximately 0.22 pounds
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Gravity - Examples
  • If gravity works on any two bodies in the
    universe, why don't we all cling to each other?
  • Replace the from previous examples with two
    people and the distance with 5 meters

1 Newton is approximately 0.22 pounds
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Physics Isaac Newton
  • English scientist who used the scientific method
    in science and mathematics
  • He was a below average student at the University
    of Cambridge that was helped by a tutor who
    recognized his talent
  • Newton studied the works of Copernicus and
    Galileo
  • In 1665, the plague forced Newton back to rural
    family farm
  • There he continued to study and created his
    theory of gravity
  • In 1687, Newton published his theories of
    gravity, etc. in his book Mathematical Principles
    of Natural Philosophy aka Principia in which he
    expanded the theories of Copernicus, Galileo, and
    Kepler
  • -explained Newtons theory of universal
    gravitation
  • -Newton developed calculus in order to prove his
    theory of gravity

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The legend is that Newton saw an apple fall in
his garden, thought of it in terms of an
attractive gravitational force towards the earth,
and realized the same force might extend as far
as the moon.
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Newtons Theory of Universal Gravitation
Newton and the Apple
Newton asked good questions ? the key to his
success.
Observing Earths gravity acting on an apple, and
seeing the moon, Newton asked whether the Earths
gravity extends as far as the moon.
(The apple never fell on his head, but sometimes
a stupid person will say that, trying to be
funny.)
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Newton Cont.
To explain all nature is too difficult a task
for any one man or even for any one age. Tis
much better to do a little with certainty, and
leave the rest for others that come after you,
than to explain all things. - Newton
Replica of Newtons Refracting telescope
...from the same principles, I now demonstrate
the frame of the System of the World Principia
Mathematica. Hypotheses non fingo.
I feign no hypothesesPrincipia Mathematica.
Original copy of Newtons Principia
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Newtons Findings
  • Newton developed calculus, new kind of math
  • Used calculus to predict effects of gravity
  • German philosopher Gottfried von Leibniz also
    developed calculus at same time
  • Each accused the other of plagiarism
  • Historians believe it was simple case of
    independent discovery

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Isaac Newton and Universal Physics
  • The implications of Newtons law were enormous
    for he demonstrated with one universal law,
    mathematically proved, that all motion in the
    universe, from the movements of the planets to an
    apple falling off a tree, could be explained
  • This Newtonian synthesis created a new cosmology
    in which the world was largely seen in
    mechanistic terms
  • Would remain the dominant cosmology until
    Einsteins concept of relativity

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Revisions to Kepler's 1st Law
  • Newton's law of gravity required some slight
    modifications to Kepler's laws
  • Instead of a planet rotating around the center of
    the Sun, it actually rotates around the center of
    mass of the two bodies
  • Each body makes a small elliptical orbit, but the
    Sun's orbit is much much smaller than the Earth's
    because it is so much more massive

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Revisions to Kepler's 3rd Law
  • Gravity also requires a slight modification to
    Kepler's 3rd Law
  • The sum of the masses of the two bodies is now
    included in the equation
  • For this equation to work, the masses must be in
    units of solar mass (usually written as M?)
  • Why did this equation work before?

Remember - for this equation to work P must be
in years! a must be in A.U. M1 and M2 must be
in solar masses
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Michael Faraday 1791 1867AD
  • English
  • Attended the lectures at the Royal Institution
  • 1825 discovered benzene when looking at the
    ingredients of oil from a dead whale
  • Did experiments with electricity
  • In 1831, Faraday discovered electromagnetic
    induction, the principle behind the electric
    transformer and generator.
  • discovery was crucial in allowing electricity to
    be transformed from a curiosity into a powerful
    new technology.
  • During the remainder of the decade he worked on
    developing his ideas about electricity.
  • He was partly responsible for coining many
    familiar words including 'electrode', 'cathode'
    and 'ion'

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Michael Faraday
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Henry Cavendish
  • Experimented with electricity
  • Tested the electric current by giving himself
    shocks and noting the pain he felt
  • In 1747, Henry Cavendish started measuring the
    conductivity (the ability to carry an electrical
    current) of different materials and published his
    results.

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Henry Cavendish
  • Cavendish had the ability to make a seemingly
    limited study give far-reaching results.
  • An example is his study of the origin of the
    ability of some fish to give an electric shock.
    He made up imitation fish of leather and wood
    soaked in salt water, with pewter (tin)
    attachments representing the organs of the fish
    that produced the effect.
  • By using Leyden jars (glass jars insulated with
    tinfoil) to charge the imitation organs, he was
    able to show that the results were entirely
    consistent with the fish's ability to produce
    electricity.
  • This investigation was among the earliest in
    which the conductivity of aqueous (in water)
    solutions was studied.

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Henry Cavendish 1731 1810 AD
  • He discovered a whole range of new gasses
  • In 1776 he added acid to marble and the gas that
    was given off was called fixed air.
  • He then dripped acid onto iron, and another gas
    was given off. It seemed that this gas was
    lighter than air and burnt so easily, so he
    called it fire air.---What we know now as
    hydrogen.
  • British
  • Was worth over one hundred million pounds
  • Son of a Lord and the grandson of the Duke of
    Devonshire
  • Spent most of his life doing science experiments
    at home alone

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Cavendish
  • Cavendish was so shy that he never told anyone
    about his discoveries.
  • It was not until 100 years later when James Clerk
    Maxwell came across his notebooks.

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