THE BIRTH OF SCIENCE

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THE BIRTH OF SCIENCE
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Definitions

• UNIVERSE everywhere that the laws of physics
  (nature) apply.
• COSMOLOGY the study of the large-scale structure
  and evolution of the universe.
• ASTRONOMY the study of the positions,
  distribution, motion, and composition of
  celestial bodies.
• SOLAR SYSTEM a star (sun) and its planets.

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Pre-Greek Paradigm

• Nature is arbitrary, capricious, mysterious, and
  terrifying.
• The Gods use the forces of nature to punish or
  reward people.
• The sun, moon, and planets are gods.
• There is no written record of speculation on the
  structure of the universe or the laws of nature.

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Egyptians and Babylonians

• The ancient Egyptians and Babylonians noted the
  periodic motions of the sun and moon, but the
  motions of the planets made no sense at all.
• The planets move with varying speeds at different
  time of the year at times they stood still and
  often reversed their courses.
• There astronomical observations were for strictly
  practical purposes. They had no interest in
  understanding them.

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The Birth of ScienceGreece(600 B.C. - 150
A.D.)
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Circa (c.) 600 B.C. Miletus

• Why did science begin here and now?
• Perhaps, the Miletans, far from home and
  therefore free of the tyranny of beliefs
  (paradigms) that society imposes on its members
  (that is, to conform) became original thinkers.

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The First Science

• Pre-Socratic Philosophers of the 4th and 5th
  Centuries B.C.
• Began to think of universe as a rational place,
  with an internal order, governed by universal,
  natural laws.
• Believed that this order is knowable by human
  beings.
• Believed that knowledge comes not through divine
  revelation and obedience to authority, but
  through open inquiry and critical evaluation of
  competing ideas.

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Thales of Miletus (c. 624 - c. 547 B.C.)
600 B.C. The Birth of Science
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Thales

• Thales seems to be the first Greek philosopher,
  scientist, and mathematician.
• One of the first to conceive of the universe in
  natural terms that nature has laws that can be
  known through a process of rational thinking.
• Conceived the principle of explaining the
  multiple of phenomena by a small number of
  theories.
• The Greek mind strove to discover a natural
  explanation for the cosmos by means of
  observation reasoning. (But not experiments.)

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Pythagoras of Samos(c. 580 - c. 500 B.C.)
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Pythagoras

• Pythagoras of Samos is often described as the
  first pure mathematician.
• He was interested in the principles of
  mathematics, the concept of number, the concept
  of a triangle, other mathematical figures, and
  the abstract idea of a proof.
• He believed that all relations could be reduced
  to numbers.

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Pythagoras Mathematics

• Today Pythagoras is remembered principally for
  his famous geometry theorem. Although the
  theorem, now known as Pythagoras's theorem, was
  known to the Babylonians 1000 years earlier he
  may have been the first to prove it.
• He is credited with being the first to conclude
  that the Earth is a sphere rather than a flat
  circular disk.

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Pythagoras Astronomy

• Pythagoras taught that
• the Earth is a sphere at the center of the
  Universe.
• the Earth moves.
• the diurnal movement of the heavens was actually
  caused by the Earths rotating on its axis.
• Mercury and Venus, which always appeared close to
  the Sun, did so because they revolved about the
  Sun rather than the Earth.

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Anaximander (c. 611 - c. 545 B.C.)

• Anaximander, Pythagoras student, believed that
  humans arose from lower animals.
• He believed that the Earth is not supported and
  sits in the center of the cosmos, and that the
  Sun, Moon, and the stars are made of fire seen
  through moving holes in the celestial globe of
  the sky.

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Anaxagoras (c. 500 - c. 425 B.C.)

• Anaxagoras held that the Sun and Moon are not
  gods that the Moon is made of ordinary matter
  with hills and valleys, and that the Sun is a red
  hot stone.
• He correctly explained the phases of the Moon,
  and eclipses of the Moon and the Sun.

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Empedocles (c. 490 - c. 430 B.C.)

• Empedocles taught that the basic elements are
  earth, water, air, and fire.
• He believed that light has a finite speed.

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Democaritus (c. 460 - c. 370 B.C.)

• Democaritus taught
• That atoms and empty space make up all existing
  matter.
• That worlds such as the earth evolve and decay.
• That there are many other worlds, some inhabited
  some not and that the milky way is composed of
  millions of unresolved stars.

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Plato(c. 428 - 347 B.C.)
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Platos Life

• Plato was born in Athens c. 428 B.C.
• He was a devoted follower of Socrates, whose
  disciple he became in 409 B.C., and the Socrates
  execution in 399 B.C. was a crushing blow.
• In 387 B.C., in the western suburbs of Athens, he
  founded a school that might be termed the first
  university.
• Plato remained at the Academy for the rest of his
  life. He is supposed to have died in his sleep at
  the age of 80 or 81.

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Platos Life

• The Academy operated until 529 A.D., when the
  Eastern Roman Emperor, Justinian, ordered it
  closed. It was the last stronghold of paganism in
  a Christian world.

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Platos Mathematics

• Plato was fond of mathematics because of its
  idealized abstractions and its separation from
  the merely material.
• Plato decided also that since the heavens were
  perfect, the various heavenly bodies would have
  to move in exact circles (the perfect curve)
  along with the crystalline spheres (the perfect
  solid) that held them in place.

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Platos Homework Problem
Plato's principal work touching in astronomy is
the Timaeus. In the Timaeus, Plato introduced
his homework problem. The problem was to
explain the retrograde motion of the planets.
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Aristotle(384-322 B.C.)
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Aristotles Life

• Aristotle was born at Stagira, in Macedonia.
• At the age of 17, he went to Athens to study at
  Plato's Academy. He remained there for about 20
  years, as a student and then as a teacher.
• When Plato died in 347 B.C., Aristotle moved to
  Assos, a city in Asia Minor.
• In 345 B.C., Aristotle went to Pella, the
  Macedonian capital, where he became the tutor of
  the king's young son Alexander, later known as
  Alexander the Great.

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Aristotles Life

• In 335 B.C., when Alexander became king,
  Aristotle returned to Athens and established his
  own school, the Lyceum.
• Upon the death of Alexander in 323 B.C., strong
  anti-Macedonian feeling developed in Athens, and
  Aristotle retired to a family estate in Euboea.
  He died there the following year.

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Aristotles Universe

• In Aristotle, Greek cosmology achieved its most
  comprehensive and systematic development.
• The Earth was the stationary center of the
  universe, around which heavenly bodies rotated.
• The whole cosmos was finite and circumscribed by
  a perfect sphere in which were set the fixed
  stars.

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Aristotles Universe

• Aristotle based the Earths uniqueness,
  centrality, and immobility not only on
  self-evidence and common sense, but also on his
  theory of the elements.
• The heavier elements, earth and water, moved
  according to their intrinsic nature toward the
  universes center (the Earth), he called the
  natural place, while the lighter elements, air
  and fire, intrinsically moved upward away from
  the center.

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Aristotles Universe

• The lightest element was aether transparent,
  purer than fire, and divinethe substance of
  which the heavens were composed.

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A "NATURAL PLACE"

• All earthly matter is centered around the Natural
  
• Place at the center of the universe. Every
• portion of Earth-
• matter strives to
• get to the center
• of the universe.
• Therefore,
• Aristotle
• deduced that
• the Earth is a
• Sphere.

Air
Fire
Water
Earth
Natural Place
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Aristotles Solution to Platos Homework Problem

• His model of the universe had the Sun, the Moon,
  the planets, and the stars, which were made of a
  fifth element only found in the heavens. The
  stars are embedded in several crystal spheres
  that rotate around the Earth.
• Aristotle's model was qualitative, but did
  address the general details of Plato's problem.

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Aristarchus(c. 310 - c. 230 B.C.)

• Aristarchus of Sámos, a Greek astronomer, was the
  first to assert that the Earth and all of the
  planets revolve around the Sun.
• In his only surviving work, On the Dimensions and
  Distances of the Sun and Moon, Aristarchus
  described a method for estimating the relative
  distances of the Sun and Moon from the Earth.

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Eratosthenes(c. 276 - 195 B.C.)

• Eratosthenes was a Greek mathematician,
  astronomer, geographer, and poet, who measured
  the circumference of the Earth with extraordinary
  accuracy by determining astronomically the
  difference in latitude between the cities of
  Syene and Alexandria, Egypt.
• He was born in Cyrene (now Shahhat, Libya). About
  276 B.C., Eratosthenes became the head of the
  library at Alexandria, Egypt. His calculation of
  the Earth's circumference was only about 15
  percent too large.

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Eratosthenes
Measuring the circumference of the Earth
SUNS PARALLEL RAYS
SYENE NO SHADOW
500 MILES
7 500

360 X
ERATOSTHENES ANSWER X 25,714 MILES
ALEXANDRIA SHADOW CASTS 70 ANGLE
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THE CORRECT ANSWER IS 25,893 MILES
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Ptolomy(c. 100 - 170 A.D.)
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Ptolomys Life

• One of the most influential Greek astronomers and
  geographers of his time, Ptolemy propounded the
  geocentric theory in a form that prevailed for
  1400 years.
• He made astronomical observations from Alexandria
  in Egypt during the years 127-41 A.D. The first
  observation that can be dated exactly was made
  by Ptolemy on March 26, 127 while the last was
  made on February 2, 41.

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The Almagest

• Ptolemy's major works have survived. The most
  important, however, is the Almagest, which is a
  treatise in thirteen books.
• This was translated into Arabic as Al-Majisti, or
  The Greatest. From this the title Almagest was
  given to the work when it was translated from
  Arabic to Latin.

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The Almagest

• The Almagest was written in Greek and published
  in Hellenistic Egypt around 150 A.D.

150 A.D. The end of the period we call The
Birth of Science.
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The Almagest

• The Almagest is the earliest of Ptolemy's works
  and gives in detail the mathematical theory of
  the motions of the Sun, Moon, and planets. This
  is Ptolemys most original and important
  contribution.
• The Almagest was not superseded for about 1,400
  years until Newton presented his heliocentric
  theory of gravitation in Principia in 1687.
• The Almagest presented a star catalog containing
  the positions of 1028 stars, which was used until
  about 1600.

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Ptolomys Model

• His geocentric model solves Platos homework
  problem. It proposes
• The Earth is round, stationary, and very small
  relative to the celestial sphere of the sky.
• The stars are fixed points of light embedded in
  the celestial sphere.
• Day and night result from the rotation of the
  entire celestial system around a fixed,
  non-rotating Earth.

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Ptolomys Model
Deferent
Epicycle
This solves Platos homework problem.
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Ptolomys Model
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Why is Ptolomy Important?

• Ptolomys geocentric theory has long been
  discarded. So, why do we study it?
• Ptolomys Almagest, more than other book,
  convinced people that seemingly complex phenomena
  of the heavens can be represented by a simple
  underlying mathematical description, one that
  afforded the possibility of predicting celestial
  events.
• This was a major milestone in the development of
  science.

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The Library at Alexandria(290 B.C. - 640 A.D.)
From Carl Sagans Cosmos
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The Library at Alexandria

• The great library and museum of Alexandria was
  established by Ptolemy I in 290 B.C. and
  flourished under the Ptolemies and through the
  Roman Period.
• This collection of manuscripts brought fame to
  the city on the Nile as the literary and
  scientific capital of the Mediterranean.
• Among the first known libraries established by a
  state for the promotion of literature and
  science, by 250 B.C., the number of scrolls
  reached 532,000 (equivalent to about 100,000
  modern books).
• In 47 B.C., during the civil war between Julius
  Caesar and the followers of Pompeii the Great,
  Caesar was besieged in Alexandria. A fire that
  destroyed the Egyptian fleet spread through some
  stores of books about 40,000 of which were
  ruined.

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Burning of the Library

• The library was open to all and held a collection
  of information that ranged from the correct
  measurement of the circumference of the Earth to
  the sexuality of humans (subjects such as
  homosexuality, sexual stimulation and sexual
  positions).
• It was these subjects that would lead to the
  library's destruction. It was been estimated that
  the library contained more than a half a million
  volumes before its destruction.
• The library at Alexandria was deliberately burned
  three times in 272 A.D. (by order of the Roman
  emperor Lucius Domitius Aurelian), in 391 A.D.
  (under the Roman emperor Theodosius I), and in
  640 A.D. (by Muslims under the caliph Umar I, c.
  581- 644).

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Burning of the Library

• The last and complete burning of the Library of
  Alexandria led to the destruction of most of the
  Greek works.
• Only those that were not in the Library survived.
• It is estimated that perhaps as many as 90 of
  the all Greek works where lost forever.

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Conclusion

• With the fall of the Roman Empire in
  approximately 500 A.D., the closing of Platos
  Academy in 529 A.D., and the final burning of the
  Library in 640 A.D., the Dark Ages were upon
  Europe.
• The Dark Ages would last about 1000 years, until
  the Renaissance began in Italy.

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Greek Contribution

• The Greeks molded the nature of mathematics,
  constructed Euclidean geometry and trigonometry,
  and applied their theoretical results to objects
  in space, the behavior of light, to mapping the
  Earth, and to determining the sizes and distances
  of heavenly bodies.
• They invented philosophy.
• The asked new questions and sought original
  answers.

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Greek Contribution

• They asked Is there was any plan underlying the
  workings of the entire universe?
• Are planets, men, animals, plants, light, and
  sound merely accidents or are they part of a
  grand plan?
• They were dreamers who arrived at new points of
  view.
• The Greeks were the first people to conceive that
  laws of nature existed.