Galileo Galilei

1
Galileo Galilei

• 1564-1642

2
Background

• Collapse of Rome - beginning of the dark ages
  (500 - 1000AD)
• passing of knowledge to the Arab world -
  translations of Greek Latin texts
• the ideas of Aristotle arrive in Europe in the
  12th C
• incorporated into university teaching

3
Problems

• Christian theology - divine revelation
• Greek philosophy - observation and human wisdom
• Aristotle said universe was eternal with no
  beginning or end
• Bible said the universe was created by God
• Aristotle - Earth imperfect
• Bible - Earth created perfectly (Garden of Eden)

4
Reconciliation (13C)Thomas Aquinas

• Divine revelation and human wisdom were
  compatible
• Earth created perfectly, with Man as the center
  of everything
• Fall from grace (eating the apple)
• Then the Earth became corrupt, but the planets
  remained perfect

5
Problem

• Copernicus - Earth not at the center of the
  universe
• if that was untrue, then all of theology was at
  risk
• teaching and believing that the Sun is at the
  center became a heresy

6
(No Transcript)
7
Background

• Family living in Florence
• Attends university at Pisa - medicine
• 1583 - discovers the pendulum (the clock)
• 1585 returns to Florence w/o degree
• He invents the hydrostatic balance
• helps father (a musician) with a study of the
  tension of strings and tones

8

• Looks for a post in a university
• gets post at the University of Pisa
• 1592 gets chair of mathematics in Padua
• invents a pump for water explains tides (wrong)
• 1600 Giordano Bruno burned at stake for espousing
  Copernicus infinity of space
• Galileo (1606) invents a kind of thermometer

9

• 1608 Hans Lipperhey (Lippershey) invents
  telescope
• 1610-11 observation of solar system
• 1609 G builds a telescope and gives it to
  Venetian Senate - gets tenure and an increase in
  salary
• 160 published Siderius Nuncius (jovian moons and
  stars)

10
History of the telescope

• Invented by Hans Lipperhey (Lippershey) in
  Holland, 1608
• based on spectacle glasses
• applied for a patent - was told it was too easy
  to copy
• letter to Galileo in May 1609 describing the
  invention

11
(No Transcript)
12
Based on two lenses Objective lens -
concave Ocular lens - concave The same as an
opera glass - 3 power
eyepiece
13
(No Transcript)
14
(No Transcript)
15
He improved the design - 20 power problems with
telescopes colored glass imperfections in the
glass poor grinding poor polishing images had
colored fringes tended toward long, narrow
telescopes
16
(No Transcript)
17
(No Transcript)
18
Discoveries

• January 1610 - moons of Jupiter
• major discovery - objects orbiting another planet
• why did the Moon stay with the Earth if the Earth
  moved?
• obviously it could be done

19
(No Transcript)
20
(No Transcript)
21
1610 Moon

• Observed that the Moon was not smooth and perfect
  (Aristotle)
• mountains
• valley
• craters
• reflected light

22
(No Transcript)
23
Moon -mountains -depressions -craters -light
areas -dark areas
24
1645
25
July 1610 Saturn

• Observed three objects - thought there were three
  planets
• really Saturn (center) and the rings on either
  side
• could not resolve the rings (bad optics)

26
Galileo Real view
27
December 1610 Venus

• Observed phases (like the Moon)
• proved that Venus revolved around the Sun
• finally we knew the order of the planets
• confirmed Copernicus

28
(No Transcript)
29
June 1611 - Sun

• More difficult to observe
• projected images onto screen
• observed dark markings on the surface
• sun spots
• Aristotle said the Sun was perfect - but it has
  blemishes

30
(No Transcript)
31
(No Transcript)
32
(No Transcript)
33
Galileos contributions

• Observational astronomy
• Experimental physics
• pendulum
• falling bodies
• projectile motion
• Mathematics
• infinitesimals

34
Talents

• Gifted self-promoter (most famous scientist in
  world)
• Well connected, politically and theologically
• Talented writer and speaker
• Wrote in Italian
• Loved argument

35
Failings

• Ignored Kepler and his laws!
• Wrong about the cause of tides (Kepler was right)
• Said meteors were atmospheric (Brahe showed
  otherwise)

36
Arguments against

• Logical arguments Aristotle
• Ignoring Galileo
• Lies

37
Difficulties with church

• 1611 - debate at dinner given by Mafeo Barberini
  1621 (fall) publishes letter on sunspots
• 1614 (Dec) Tommaso Caccini preaches against
  Galileo
• 1615 (Jan) Superior of TC writes to apologize to
  Galileo

38

• 1615 (Feb) complaint sent to the Inquisition
• 1615 (Mar) Galileo writes to Vatican
• 1616 (Feb) Paul V instructs Cardinal Bellarmine
  to warn Galileo. Forbidden to discuss Copernicus
• 1616 (Mar) On the revolutions placed on Index
• 1621 Paul V dies - replaced by Gregory XV

39

• 1623 Gregory dies - replaced by Bellarmine (Urban
  VIII)
• 1624 Galileo visits Urban VIII six times. He is
  assured that he can write about Copernicus but as
  an hypothesis only
• 1639 Kepler dies
• 1630 (Feb) Urban gives Galileo a pension
• 1632 (Feb) Dialogue concerning the two chief
  world systems published

40
Problems with Dialogue

• Problems with Roman censure
• Galileo wrote a preface - hypothetical only
• Book was approved and printed
• Discussion between three characters
• Salviati - represents Galileo
• Sagredo - man of good sense
• Simplicio - Aristotelean

41

• Salviati discusses the explanation of many
  phenomena
• Sagredo is persuaded by these arguments
• Simplicio does not shine - ridiculed
• At the end, Simplicio make the argument about God
  creating the universe
• This is the argument of Urban VIII
• Disaster follows

42

• 1632 (summer) Urban prohibits distribution of
  Dialogue
• 1632 (Sept) case referred to the Inquisition
• 1632 (Oct) Galileo summoned to Rome
• 1633 (Feb) Galileo arrives
• April he is examined by the Inquisition
• he confesses to lesser charges
• sentenced to house arrest
• Wrote Discourse on two new sciences

43

• 1638 Writes a book summarizing his studies of
  mechanics and kinematics
• 1642 he dies