1. Scientists of the Scientific Revolution
Clockwise from top: Kepler, Copernicus, Newton, Galileo, Descartes, and Ptolemy

3. Astronomy

5. Historical figures in the Copernican Revolution
Ptolemy – the geocentric model, that the Earth is at rest at the center of the Universe.
Copernicus – published the heliocentric model.
Galileo – his observations by telescope verified the
heliocentric model.
Kepler – deduced empirical laws of planetary motion from Tycho’s observations of planetary positions.
How was this knowledge of the solar system discovered?
It is a dramatic story in the History of Science. So today’s lecture is mainly historical. Then next time we’ll see how Isaac Newton explained the motion of the planets with his theories of motion and gravity.
The slide lists the famous names in the Copernican Revolution.
Ptolemy was a Greek astronomer who lived in Egypt during the time of the Roman Empire. He was born about 85 AD – 85 years after the birth of Jesus of Nazareth. He wrote a famous book on astronomy, which tried to show that the Earth is at the center of the universe, based on astronomical observations of his time. In the Ptolemaic model, all heavenly bodies revolve around the Earth -- stars, the sun, the moon, and the planets.
However, Ptolemy and others knew that the geocentric model was really not very accurate; so they tried to fix it up in various ways to agree with the observations. They had to postulate complicated orbits around the Earth, with cycles and epicycles, to agree with the observations on planetary motions. The Ptolemaic theory – the geocentric model -- survived for 1,400 years, in spite of its weaknesses. {READ}
Copernicus was trained to be a priest, and held an office in the Roman Catholic Church in Poland. But he spent his life in astronomical studies. At the end of his life he published the theory that the Earth and planets revolve around the sun. {READ}
Galileo and Kepler lived some years after Copernicus. They never met in person but they did correspond and they respected each other. Their work proved that Copernicus was right. {READ}
Finally, Newton developed a complete theory of planetary orbits. It is still used today.
Newton – developed the full theory of planetary orbits.
7/14/06
ISP A

6. The Copernican Revolution
This timeline shows the life spans of the four most important scientists in the Copernican Revolution. This advance in science was at the core of the Scientific Revolution.
Copernicus lived at the same time as Christopher Columbus. Galileo and Kepler were contemporaries, a generation after Copernicus. Then Newton completed the work in the next generation. Newton lived at the time of the first English colonies in America.
[Copernicus 1473 to 1543; Galileo 1564 to 1642; Kepler 1571 to 1630; Newton 1643 to 1727]
The idea that the sun and not the Earth is the center of the universe -- or at least at the center of the solar system -- started with Nicolas Copernicus.
7/14/06
ISP A

7. The Geocentric Theory vs. The Heliocentric Theory

8. The Geocentric Theory
The earth is located at the center of the universe and all the planets revolve around the earth.

9. Geocentric Cont…..
The Geocentric theory was believed by the Catholic church especially because the church taught that God put earth as the center of the universe which made earth special and powerful.
The idea of the Earth actually moving was widely felt as a foolish suggestion because, as they saw it, if the Earth was moving they would be able to feel it.

10. Aristotle ( B.C.)
Developed an early model based on the concept of uniform circular motion. He placed the earth at the center of the universe and all of the planets, sun and stars around it.
When Aristotle lived, if a person could “reason” out why something happened, then you didn’t need to do any experiments to see what would happen.

11. Scientific Revolution” Helio-Centric Theory of the Universe
Sun at the center of the universe,
with the planets orbiting the sun
Created by Nicholas
Copernicus ( ),
a Polish astronomer

12. In the realm of change, the natural motion of earthy materials was to seek the center of the universe.
This is why Aristotle placed the earth at the center of the cosmos.
This is also his explanation for why objects fall when dropped.
A dropped object is just following its natural tendency to seek the center of the universe.

13. Aristotle reasoned that if the earth rotated about its axis, we should fly off into space. Since we don't, the earth must be stationary.
It would be almost 1900 years before Galileo introduced the concepts of gravity and inertia that explain why these effects are not observed even though the earth does move.

14. Ptolemy (140 A.D.)
Ptolemy advanced the geocentric theory in a form that prevailed for 1400 years.
He added mathematics to support the theory

15. How did Ptolemy Explain this Problem?
Ptolemy used geometric models to predict the positions of the sun, moon, and planets, using combinations of circular motion known as epicycles.
An epicycle is an orbit within an orbit
Having set up this model, Ptolemy then went on to describe the mathematics which he needed in the rest of the work.

16. Ptolemy’s Model – Epicycles Included

17. The Heliocentric Theory
The Sun is the center of our solar system

18. Copernicus ( )
Polish astronomer who advanced the theory that the Earth and other planets revolve around the Sun. This was highly controversial at the time.
The Ptolemaic model had been widely accepted in Europe for 1000 years when Copernicus proposed his model.

19. Discoveries in Astronomy, Physics, and Math
Early scientists
Made significant contributions in astronomy, physics and math
Began to explain complexities of solar system, limits of physical world
Nicolaus Copernicus, Polish astronomer, among first
Copernicus
Found geocentric theory of movement of sun, moon, planets not accurate
Concluded sun, not earth, near center of solar system
Heliocentric theory, earth revolves around sun
Copernicus’ theory
Idea of earth orbiting sun was not completely new
Copernicus developed detailed mathematical explanation of process
Was first scientist to create complete model of solar system

20. On the Revolutions of the Heavenly Spheres
Copernicus’ famous book not published until last year of his life
Knew church would oppose work
Work contradicted teachings of church
Weaknesses of theory
Mathematical formulas did not predict positions of planets well
Copernicus did not want to be ridiculed for weaknesses
Died 1543 after work published, other scientists expanded on ideas

21. Copernicus was told by many scholars that he should make his new findings accessible to others by publishing it.
In 1543 the book called "On the revolutions of the heavenly bodies" was released.
Copernicus's book had a great impact that angered the Catholic and Protestant Church.
The Church became so angry – the Geocentric theory made human beings seem closer to God and since earth was in the center that meant humans were more special.
The heliocentric theory changed that perspective completely, making humans lose that position in the universe.

22. Nicholas Copernicus (1473-1543)
Polish priest studied in Italy
returns to Poland and works on Astronomy
writes De Revolutionibus Orbitum Coelestitum (On the Revolutions of Heavenly Spheres)
Earth is just another planet with a 24 hour rotation
retains circular planetary motion (perfection of the sphere).
Simplicity as best explanation
keeps Ptolemaic circular patterns and epicycles
places sun at center of solar system
Manuscript not accepted by Church, banned in 1616
legalized in 1835

23. Copernicus On the Revolutions of the Heavenly Spheres.
Proposed a sun-centered view. (helio-centric)
Universe consisted of 8 spheres.
Planets including earth rotated around the sun but the moon revolved around the earth.
Apparent revolution of the sun and stars around the earth was due to the rotation of the earth.
Did not reject the Ptolemaic vision of the fixed spheres.
His views did not make a big splash either pro or con, but there was growing dissatisfaction with the Ptolemaic view.

24. Nicolaus Copernicus (1473-1543)
Polish astronomer and mathematician
Introduced to scientific world when he attended the University of Krakow in Poland in 1492
Appointed as a canon in the cathedral of Frauenburg where he remained for the rest of his life
Rheticus, a student Copernicus took on in 1539, convinced Copernicus to allow him to publish his works before death

25. Copernicus’s Scientific Theories:
Considered the founder of modern science
Believed that the earth was round and the earth revolved around the sun (contrary to popular belief)
The heliocentric theory was not new, but Copernicus established the mathematical basis
To avoid the risk of persecution, excommunication, or imprisonment because his were revolutionary and contrary to church beliefs, Copernicus worked in privacy for more than 30 years; just before his death, friends helped to published his work
Copernicus’s theory was first taught in several universities in the 1500s and permeated the scientific world by 1600

26. Copernicus Cont:
“Finally we shall place the Sun himself at the center of the Universe. All this is suggested by the systematic procession of events and the harmony of the whole Universe, if only we face the facts, as they say, 'with both eyes open’.”- Copernicus
“The earth also is spherical, since it presses upon its center from every direction.”-Copernicus

28. Nicolaus Copernicus The Earth moves, in two ways.
It rotates on an axis (period = 1 day).
It revolves around the sun (period = 1 year).
Part 2 -- Copernicus (15 minutes)
The Copernican model was based on the hypothesis that the Earth moves, in two ways.
{READ}
7/14/06
ISP A

29. The Copernican Universe

31. The heliocentric model
Copernicus believed that the Earth rotates once per day, and revolves around the Sun once per year, as shown in the figure.
Do you think these motions of the Earth affect you? Well, they produce day and night; and they produce the seasons. {READ reasons for seasons}
The axis of rotation of the Earth is constant (points always in the same direction) and is at an angle to the plane of the orbit. Therefore the solar illumination in the northern or southern hemisphere varies throughout the year as the Earth goes around the sun. Solar illumination is greatest during the summer and least during the winter.
A common misconception is that the Earth is closer to the sun during the summer (so that the summer is hotter). That’s false! The distance to the sun has nothing to do with the seasons. Perihelion occurs in December. In any case, summer in the northern hemisphere is winter in the southern hemisphere; and vice versa. If the distance to the sun were relevant, then the two hemispheres would have the same seasons. But, on the contrary, their seasons are out of phase by 6 months. Right now – today -- it is winter in Australia and South America.
The figure shows the solstices and equinoxes (A, B, C, D).
At winter solstice (for the N hemisphere) the axis of rotation points away from the sun, so that the N hemisphere gets the least solar radiation. At summer solstice (for the N hemisphere) the axis points toward the sun, so that the N hemisphere gets the most solar radiation.
The reasons for seasons – the Earth travels around the sun, and its axis of rotation is tilted by 23.5 degrees to the plane of the orbit. In July, the northern hemisphere is getting more sunlight than in January.
7/14/06
ISP A

32. The reasons for seasons
The reasons for seasons. This slide illustrates summer in the northern hemisphere.
Note that (1) the period of daytime (dawn to dusk) is more than 12 hours in the northern hemisphere, because more than half the northern hemisphere is in sunlight at any give time; however, the period from dawn to dusk is less than 12 hours in the southern hemisphere.
Also, (2) the solar radiation is more direct, concentrated, intense in the northern hemisphere.
And, (3) the sun is higher in the sky.
DEMO [1/3]
Flashlight at an angle and the intensity or concentration of light
7/14/06
ISP A

33. The Copernican Model
The Scientific Revolution (1543 – 1687) was driven by astronomy. The famous names are
Copernicus… Galileo… Kepler… Newton…
After their advances in science, the human view of the universe had changed dramatically!
A question: At which position in our orbit around the sun are we today? A, B, C, or D?
Now… this picture was the beginning of a kind of conflict between science and religion. Galileo was tried for heresy in 1633, in the midst of the scientific revolution (next slide!) His crime was to argue in favor of the Copernican model.
7/14/06
ISP A

34. Giordano Bruno: 1548 – 1600 AD Italian monk
Believed Copernicus was right and that the earth revolved around the sun
Believed the earth was alive because it moves through space
Believed the universe is huge and everything is made up of atoms
He did not do original research; just used reason and speculation.
Bruno wandered around Europe teaching and writing for a living.
He returned to Italy and found trouble

35. Bruno vs the Inquisition
Bruno had been offered a teaching job in Venice and thought his employer would protect him.
Instead, Bruno was arrested by the Inquisition for not supporting the Geo-Centric Theory
After seven years in prison, Bruno was tried as a heretic.
On February 6, 1600, he was burned at the stake for his scientific ideas.

36. The Baroque Setting
In the 1600s church through counter-reformation much stricter
G. BRUNO (Italian; 1548) proposes that the Sun is just one star out of an infinite number  burned at the stake for heresy 1600
30 Years War ( ) between religions
New inventions: telescope, air pump, etc.

38. Tycho Brahe Believed geocentric uni-verse is Scriptural
Built equipment to prove Copernican model wrong
Greatest naked-eye astronomer of all time
Proposed a geocentric model that saved all appearances

39. Tycho Brahe (1546-1601) Danish astronomer
Established an observatory to study heavenly bodies
Accumulated a lot of data on planetary movements
His tables of astronomical observation was used by Kepler to prove Copernicus’s
helio-centric hypothesis

40. Brahe Cont:
Believed that the development of astronomy relied on accurate observation
Made lots of astronomical observation with the naked eye
Built and calibrated numerous new instruments including:
Created a domicile and observatory which he called Uraniborg

41. Tycho Brahe’s original model

42. Modified Tychonic Model Modified Tychonic model explains aberration
annual Doppler shift
parallax

44. Azimuth Quadrant made in
Brahe Cont.
Uraniborg
Azimuth Quadrant made in
1577.
Instrument for measuring altitude
Instrument to measure angles

45. Tycho Brahe – The Data Taker
Key question: Where are things?
Catalogued positions of planets in Uraniborg and Prague
Working without telescope
Data ten times as accurate as before
Died at banquet binge drinking
TYCHO BRAHE (Danish)
collects detailed and accurate (1-2 arcmin accuracy) observations of stellar and planetary positions over a period of 20 years
shows that comets and novas are extralunar contra Aristotle; comets pass through planetary spheres
His research may have cost 5-10% of the total GNP of Denmark at that time!
JOHANNES KEPLER (German) reduces Tycho's data and by triangulation determines the orbits of the planets, including Earth's. The "baseline" is given by the Earth moving in its orbit.
Not a simple problem, since the orbit of the Earth was not known beforehand, and the other planets don't sit still while the Earth is moving around!
Tycho Brahe (1546–1601)

46. Tycho Brahe - An Observer
Tycho Brahe was a prominent scholar and aristocrat in Denmark in the mid-late 1500's
He made a huge number of observations of the stars and planets, all with the naked eye
Even without a telescope, he was very accurate in his measurements
Also recorded the appearance of comets and supernovae
The Tycho supernova remnant is still visible today
Tycho ( )

47. Tycho Brahe Tycho Brahe observing
collects detailed and accurate (1-2’ accuracy) observations of stellar and planetary positions over a period of 20 years
His research costed 5-10% of Danish GNP
shows that comets and novas are extralunar contrary to Aristotle
Shows that stars can change
(Supernova of 1572)
TYCHO BRAHE (Danish)
collects detailed and accurate (1-2 arcmin accuracy) observations of stellar and planetary positions over a period of 20 years
shows that comets and novas are extralunar contra Aristotle; comets pass through planetary spheres
His research may have cost 5-10% of the total GNP of Denmark at that time!
JOHANNES KEPLER (German) reduces Tycho's data and by triangulation determines the orbits of the planets, including Earth's. The "baseline" is given by the Earth moving in its orbit.
Not a simple problem, since the orbit of the Earth was not known beforehand, and the other planets don't sit still while the Earth is moving around!
Tycho Brahe observing

48. Brahe and Kepler Observations Brahe, Danish Astronomer
Wrote book proving bright object over Denmark sky was newly visible star
Called it supernova, distant exploding star suddenly visible on earth
Book impressed Denmark’s King Frederick II
Gave Brahe money to build two observatories
Brahe used observatories
Developed system to explain planetary movement
Believed sun revolved around earth
Other five known planets revolved around sun
Observations
Hired as Brahe’s assistant to form mathematical theory from measurements of planets
Published result of measurements of orbit of Mars after Brahe’s death
Kepler, German Mathematician

49. Johannes Kepler - A Theorist
Shortly before his death, Tycho began working with another scientist named Kepler
Kepler was put to the task of creating a model to fit all of Tycho's planetary data
Kepler spent the remainder of his life formulating a set of laws that explained the motion of the planets
Kepler ( )

50. Kepler’s Beginnings Astrologer and Mystic
Tried to find “music in the skies”
Tried to explain distances of the 5 known planets by
spheres resting on the
5 mathematical bodies
 pre-scientific

51. Johannes Kepler (1571-1630) Student of mathematics and astronomy
studied with Tycho Brahe
tested hypothesis after hypothesis until he determined that planets move in ellipses
Three Laws of Planetary Motion
planets move in ellipses with sun as one focus
velocity of a planet is not uniform
equal area of the plane is covered in equal time by the planets.

52. Johannes Kepler—( )
Built on the detailed observations of Tycho Brahe.
Confirmed Copernicus’s heliocentric theory
Worked out the laws that governed planetary motion.
Discovered that orbits were elliptical, not circular.
Killed off the Ptolemaic theory of crystalline spheres and a perfect heaven.
Opens the door to the question of what the planets and stars are made of and what governs their motion.

53. Johannes Kepler ( )
Used Brahe’s work to successfully prove Copernicus’s helio-centric model mathematically
However, he disproved Brahe’s claim that planets move in circular motion – found that they move in ellipses
Discovered that the speed of planets increase as they near the sun and decrease as they go away from it
Discovered three laws of planetary motion
the planets orbit the sun in elliptical orbits; the sun is at one focus of the ellipse
An imaginary line drawn from the center of the sun to the center of a planet will sweep out equal areas in equal intervals of time
The ratio of the squares of the periods of any two planets is equal to he ratio of the cubes of their average distance from the sun
Worked in optics, discovered two new regular polyhedra, created the first proof of logarithms, and created a way to find the volume of solids of revolution (which influenced calculus)
Proof of logs based off of the work of Napier and Euclid

54. Kepler Cont.:
Very religious (protestant); believed in Intelligent Design, and that God made the Universe according to a mathematical plan
Math was considered a way to find truth, so Kepler thought that this gave man a way to find and understand the truth of the Universe
Worked as an aide to Tycho Brahe and continued Brahe’s work and used it in his own work
Established the idea of observational error

55. Johannes Kepler (1571 – 1630)
… discovered three empirical laws of planetary motion in the heliocentric solar system
Each planet moves on an elliptical orbit.
The radial vector sweeps out equal areas in equal times.
The square of the period is proportional to the cube of the radius.
Part 4 – Kepler (20 minutes)
{READ first part}
Johannes Kepler was a contemporary of Galileo. Galileo lived in Italy, Kepler in Northern Europe, mostly Germany. Galileo was a Catholic; Kepler a Lutheran.
Kepler held the position of Mathematician to the Holy Roman Emperor. His most important work was to study planetary observations, and to relate them to the heliocentric model of Copernicus.
The result of years of arduous mathematical work was summarized in three empirical laws of planetary orbits.
{READ the three laws}
So Kepler discovered the true behavior of the planets in the Solar System.
Kepler lived at a time of great turmoil in Europe. The Reformation and the Counter-Reformation led to terrible wars between Protestants and Catholics. Some rulers persecuted people for religion. While the man-made chaos was occurring all around him – sometimes even affecting Kepler himself – Kepler was discovering the natural order in the heavens.
(needed for the CAPA)
7/14/06
ISP A

56. Kepler’s First Law
The orbits of the planets are ellipses, with the Sun at one focus
Orbits turn out not to be circles nor eccentric circles but ellipses (which can be made with string and thumbtacks as shown)
The sun is at one focus (not the center).
A foreshortened circle

57. Kepler's First Law
Kepler first noted that the orbital path of a planet around the Sun is an ellipse, not a perfect circle
The Sun lies at one of the foci of the ellipse
The eccentricity of an ellipse is a measure of how 'squished' from a circle the shape is
Most planets in the Solar System are very close to a perfect circle
Eccentricity, e ~ 0 for a circle
Focus
Focus
Kepler's 1st Law: The orbital paths of the planets are elliptical with the Sun at one focus.

58. Kepler's First Law
=closest to the Sun
=farthest from the Sun

59. Kepler’s Second Law
An imaginary line connecting the Sun to any planet sweeps out equal areas of the ellipse in equal times
conservation of angular momentum: same effect makes skaters speed up when they draw in their arms

60. Kepler’s Third Law
The square of a planet’s orbital period is proportional to the cube of its orbital semi-major axis:
P 2  a3
a P
Planet Orbital Semi-Major Axis Orbital Period Eccentricity P2/a3
Mercury
Venus
Earth
Mars
Jupiter
Saturn
Uranus
Neptune
Pluto
(A.U.) (Earth years)
more distant planets move more slowly and have longer "years".
Kepler can determine ratio of sizes of the planets' orbits but not the actual sizes; this is because he uses orbit of Earth as baseline for triangulation. If we know the size of one planet's orbit, we can find the rest.
Earth's orbit (1 AU)=93 million mi=150 million km=8 light minutes. Nowadays determined by radar ("radio detection and ranging") bounced off Venus.

61. Kepler's Second Law
Kepler also noticed that the planets sweep out equal areas in their orbit over equal times
Notice that this means the planet must speed up and slow down at different points
If it takes the same amount of time to go through A as it does C, at what point is it moving faster?
C, when it is closest to the Sun
Kepler's 2nd Law: An imaginary line connecting the Sun to any planet sweeps out equal areas of the ellipse over equal intervals of time.

62. Kepler's Third Law
Finally, Kepler noticed that the period of planet's orbit squared is proportional to the cube of its semi major axis
This law allowed the orbits of all the planets to be calculated
It also allowed for the prediction of the location of other possible planets
Kepler's 3rd Law Simplified
NOTE: In order to use the equation as shown, you must be talking about a planet in the Solar System, P must be in years, and a must be in A.U. !!!

63. Kepler's Third Law - Examples
Suppose you found a new planet in the Solar System with a semi major axis of 3.8 A.U.
A planet with a semi major axis of 3.8 A.U. would have an orbital period of 7.41 years
years

64. Kepler's Third Law - Examples
Suppose you want to know the semi major axis of a comet with a period of 25 years
A planet with an orbital period of 25 years would have a semi major axis of 8.55 A.U.
A.U.

65. Compare the heliocentric model to naked-eye astronomy
How did Kepler determine the planetary orbits?
Compare the heliocentric model to naked-eye astronomy
Mars
The inner planet is Earth; the outer one is Mars. Plot their positions every month. Mars lags behind the Earth so its appearance with respect to the Zodiac is shifting.
Earth
The figure shows 12 months of the orbital motion of the Earth and Mars. Their positions are color coded. In 12 months, the Earth travels once around the sun; Mars travels only a little more than half-way around in that time.
The black arrows show the directions in which Mars would be observed on the background of the Constellations of the Zodiac. As the months pass, the position of Mars in the Zodiac shifts around in an observable way as a “wandering star.”
This figure shows how the orbits (of Earth and Mars) would determine the sky positions of Mars. But Kepler had to do the opposite. By taking the observed sky positions and working backwards, Kepler was able to plot out an accurate orbit for Mars – consistent with the naked eye astronomy.
Physicists hold Kepler in awe. The feat of computation that was required to discover Kepler’s 3 laws of planetary motion is something no one else could have done. Kepler called it “my war with Mars”.
Where did Kepler get the motivation to study planetary observations? Partly it was religious – he was revealing the mind of God. But also, part of his job as Imperial Mathematician was to cast horoscopes for the Emperor.
The most complete data had been collected over a period of many years by Kepler’s predecessor, Tycho Brahe of Denmark.
7/14/06
ISP A

66. KEPLER
Instrument to show relative distances of planets according to Copernican System
“And to us Jupiter, like Mars, and in the morning Mercury and Sirius, appeared four-cornered. And one of the diameters running between the corners was blue, the other red, in the middle the body was yellow, and amazingly bright. Account of personal observations...:”

67. Kepler solved main problem of Copernican theory
Kepler’s Solution
Kepler solved main problem of Copernican theory
Copernicus assumed planets orbited in circle
Kepler found assumption untrue
Proved planets orbited in oval pattern, ellipse
Wanted to prove Copernicus wrong, instead proved heliocentric theory correct
Kepler’s mathematical solar system model also correct

68. Galileo on Scripture: The Scriptures teach us how to go to heaven, not how the heavens go.

69. Galileo ( )
An Italian scientist, Galileo was renowned for his contributions to physics, astronomy, and scientific philosophy.
He is regarded as the chief founder of modern science.
Galileo was condemned by the Catholic Church for his view of the cosmos based on the theory of Copernicus.

70. Galileo Galilei – The Experimentalist
Did experiments (falling bodies) rather
than studying Aristotle
Major Works
Siderius Nuntius (1610)
Dialogue concerning the Two Chief World Systems (1632)
The latter discusses Copernicus vs Ptolemy ban by Church (1633)
revoked by pope 1992
(1564–1642)
Telescope invented in Holland in 1608 (HANS LIPPERSHEY)
1616 Galileo ordered to treat Copernicanism as hypothetical
1633 Galileo condemned to permanent house arrest (despite papers giving permission to publish hypothetically)
1992 Vatican acknowledges error after 359 years
Galileo's contributions put science firmly on the basis of observation.
Argued that the Church should not make scientific positions as articles of faith nor should biblical arguments be applied to science
Wrote in Italian rather than Latin

71. Galileo’s Places Born at Pisa, Tuscany Childhood in Florence, Tuscany
Studies at University of Pisa
Begins teaching at Pisa
Gets a position at Padua, Province of Venice
Stays for 18 years

72. Galileo’s Places (cont’d)
Returns to Florence, Tuscany in 1610 under Grand duke Cosimo II.
1633: Trial in Rome
From 1633: house arrest in Acetri, near Florence
1637: loses eyesight
1992: ban on Galileo lifted by Pope John Paul II.

73. Galileo’s discoveries in Astronomy
Galileo did not invent the telescope, but when he heard about the invention he figured out how to build telescopes. He had the best telescopes of his time. He was the first person to use telescopes to look at the heavenly bodies. He was first, so he made the discoveries.
 Craters and mountains on the moon
 Moons of Jupiter
 Phases of Venus
 The Milky Way consists of innumerable stars.
 Sunspots move across the sun’s face.
All of these favored the Copernican (heliocentric) model.
Galileo was professor of mathematics, but also interested in the physical world. His believed that observations and experiments are the only way to know nature.
We have seen that his discoveries in physics came from observations and measurements. His discoveries in astronomy came from telescopes.
{READ the slide}
7/14/06
ISP A

74. Galileo Galilei (1564–1642)
Astronomical observations that contradict Aristotle:
Observed mountains on the Moon, suggesting that the Earth is not unique
Sunspots; suggests that celestial bodies are not perfect and can change
Observed four moons of Jupiter; showed that not all bodies orbit Earth
Telescope invented in Holland in 1608 (HANS LIPPERSHEY)
1616 Galileo ordered to treat Copernicanism as hypothetical
1633 Galileo condemned to permanent house arrest (despite papers giving permission to publish hypothetically)
1992 Vatican acknowledges error after 359 years
Galileo's contributions put science firmly on the basis of observation.
Argued that the Church should not make scientific positions as articles of faith nor should biblical arguments be applied to science
Wrote in Italian rather than Latin
Observed phases of Venus (and correlation of apparent size and phase); evidence that Venus orbits the Sun
Also observed
the rings of Saturn
that the Milky Way is made of stars

75. Galileo’s sketch of the moon as seen from his telescope
A photograph of the moon
Here are a couple of pictures of the moon.
The first is Galileo’s sketch…{READ}
The second is a modern photograph…{READ}
So Galileo could see that the moon is not some ideal heavenly disk, but a real material sphere with craters and mountains. It was like another little world. However, as was often the case with Galileo, many philosophers did not want to accept his new knowledge. They just couldn’t bring themselves to admit that their whole world view was based on errors.
In a letter to Kepler, Galileo wrote… “{READ the quote}
“What do you think of the foremost philosophers of this university? In spite of my oft repeated efforts and invitations, they have refused, with the obstinacy of a glutted adder, to look at the planets or Moon or my telescope.” (letter to Kepler)
7/14/06
ISP A

76. These ideas could be dangerous.
Galileo made many specific discoveries in astronomy, through observations by telescope.
The general implications…
● The planets are objects like the Earth – masses – rather than some kind of special heavenly objects. Or, to put it another way, the Earth is just another planet.
● The planets, including Earth, travel around the sun.
● The Universe is a lot bigger than we can see by the naked eye.
{READ first line}
Galileo also asked what his discoveries would imply about the universe in general.
The general implications of his discoveries were significant evidence for the Copernican Model.
{READ the rest}
These ideas could be dangerous.
7/14/06
ISP A

77. Galileo Galilei (1564-1642) Astronomy Laws of Motion
used a telescope, proved the heavens are not perfect (craters on moon)
supported Heliocentric system
Laws of Motion
dropping weights from the Tower of Pisa
imagined motion without constraint!!!!
Thought of inertia
Problems with the church
argues for separation of science and theology because we are endowed with reason
1633 banned by Church and house arrest
must recant heliocentric system to save neck.
Swinging pendulum while at U of Pisa, times with pulse and helps determine notion of equal time for each swing
drop 2 balls of different weights form a tower - slight difference: based on aerodynamics, Galileo ultimately forced from school by partisans
creates first telescope
discovers craters of moon and spots on sun
“stars” orbiting Saturn
published “The Dialogue on the Two Great Systems of the World”

78. Galileo’s Books
Galileo published his discoveries and support for the Copernican model in two books published in 1616 and 1632.
Galileo was unusual for the time because he wrote in Italian rather than Latin like most scholars.
Galileo also took great pains to make his books interesting often writing them in the form of dialogues rather than dry, boring dissertations.
After his first book, "Starry Messenger", was published he was warned by the Church not to publicly support Copernicism again.

79. Reactions to Galileo Italy and Spain
More freedom in France, England and Holland
University of Padua was under Venice, the most anti-clerical state in Europe; Copernicus, Galileo and Harvey studied there
Protestants as hostile as Catholics on Biblical grounds, less state control in Protestant nations and in the end Protestant nations become more liberal than at first.

80. Galileo Galilei: 1564 – 1642AD Italian
Was a Professor of Mathematics at Pisa University
Became interested in science after reading the works of Copernicus and Bruno
These books convinced him that the earth revolved around the sun.
He also made huge discoveries in physics.
He proved that a pendulum swings the same time no matter the size.
He used mathematical rules to explain this; it was the first time math had been used to describe an object in motion.

81. Galileo
These discoveries proved once again that Aristotle’s theories were wrong.
The moon wasn’t a perfect round ball as the ancient Greeks believed, but had bumps and craters.
In 1609, he switched from being a physicist to being an astronomer.
He heard about the newly-invented telescope and built his own.
He used it to discover 4 moons of Jupiter and the mountains on the moons.

82. Galileo Continued
Watched as the planets Venus and Saturn travel around the sun
This proved that the Earth was not the center of the solar system.
Galileo wrote a book in 1610 about his discoveries
This is where his trouble with the Catholic Church begins.

83. Galileo Galilei:
In 1609 Galileo built his own telescope to observe the night skies
Galileo worked with Kepler who discovered by using convex lens it would increase the magnification
Galileo’s telescope developed in 1609, modeled based off other telescopes
Could magnify three times more than other telescopes; his later telescope magnified twenty times
He could see the moon, four satellites, a supernova,
the phases of Venus, and sunspots

85. Galileo Galilei ( )
First European to make systematic observations of the heavens using a telescope.
Established that the planets were made of material stuff quite similar to the earth.
The Starry Messenger.
Publicized the shift in scientific thinking away from the Ptolemaic view.

86. Galileo Galileo (1564-1642) The Starry Messenger
Published in 1610
Stunned contemporaries and did more to make Europe aware of the new picture of the universe than the mathematical theories of Copernicus and Kepler
Galileo, the Church and Inquisition
Dialogue on the Two Chief World Systems: Ptolemaic & Copernican
Placed under house arrest and during his final eight years Galileo studied mechanics discovering the principles of inertia & force

87. Science and the Church Galileo’s Theories Trial House Arrest
Brought him into direct conflict with the church
Church leaders pressured him not to support ideas of Copernicus
Dialogue concerning Two Chief World Systems, 1632, showed support
Trial
Pope Urban VII ordered Galileo to Rome to stand trial before Inquisition
Church wanted to stamp out heresy, or dissenting views
Trial held, April 1633
House Arrest
Galileo stated would not use Copernican theory in work
Received lenient sentence in return
Pope ordered Galileo under house arrest, where he spent rest of life

88. Trial Before the Inquisition
Galileo abided by this edict until 1632 when he published "A Dialogue on the Two Chief World Systems". This book's outright support for the Copernican model and its ridiculing of the Ptolemaic model earned Galileo a trial before the Inquisition.
Galileo was accused of heresy and sentenced to house arrest for life. However, he got off easily compared to fellow Italian Giordano Bruno who was burned at the stake in 1600 for teaching Copernican ideas.

90. Galileo and the Church In 1616, Galileo promised to give up his ideas.
But he then published a book making fun of the Catholic’s teaching of the Geo-Centric Theory.
In his book, he uses a fictional dialogue or conversation to make fun of the Church.
The character who backed the Church’s views was called Simplicius, which means stupid.
In 1633 after a series of warnings against his teaching, Galileo was put on trial before the Inquisition
The charge was heresy with the likely punishment of death
He was 70 years old at the time

91. Galileo’s Letter to Castelli
“I am inclined to think that the authority of Holy Scripture is intended to convince men of those truths which are necessary for their salvation, and which being far above man's understanding cannot be made credible by any learning, or any other means than revelation by the Holy Spirit.  But that the same God has endowed us with senses, reason, and understanding, does not permit us to use them, and desires to acquaint us in any other way with such knowledge as we are in a position to acquire for ourselves by means of those faculties, that it seems to me I am not bound to believe, especially concerning those sciences about which the Holy Scriptures contain only small fragments and varying conclusions; and this is precisely the case with astronomy, of which there is so little that the planet are not even all enumerated....”

92. Galileo and the Church
To save his life, Galileo confessed that the Earth did not go around the sun.
According to legend, he muttered under his breath: “But it still moves.”
He was sentenced to life imprisonment and ended up locked in his own home where he went blind and had to give up his scientific work.
Some historians believe Galileo was tortured, because he suffered from weakened muscles in his gut from the stretching rack.
Others say he was just shown the torture chamber to scare him.

93. Galileo the Heretic Church found his findings dangerous. Why?
Removed Humans from the center of the earth,
Did away with the perfection of circular orbits and
No longer had God in a fixed place.
Inquisition condemns this view; he recants under pressure.
Is placed under house arrest for the last 8 years of he life.
Attitude of the church crimped further scientific inquiry into the heavens in Italy

94. Galileo + Church:
While at the University of Padua, Galileo became very much involved with Copernicus’s heliocentric theory of the universe
Galileo’s invention of the telescope enabled him to make observations that supported and proved the Copernican theory and encouraged him to publicly support it
For this and for other letters, works, etc. that criticized the scripture as simply symbolical, Galileo was summoned to Rome where he was tried by the Inquisition in 1633
They forced him to recant his belief in the Copernican Theories
In April of 1633 Galileo is interrogated before the Inquisition. He agrees to plead guilty to a lesser charge in exchange for a more lenient sentence.
Galileo was sentenced to house arrest in Siena
Only in 1992 did the Church officially admit their mistake with the Galileo Trial
The Trial caused fear among scientists and encouraged them to keep their findings from the Church and thus from the public
In February 1632, Galileo published his book, Dialogue Concerning the Two Chief Systems of the World – Ptolemaic and Copernican

95. Galileo’s Forced Statement
I, Galileo, son of the late Vincenzo Galilei, Florentine, aged seventy years, arraigned personally before this tribunal, and kneeling before you, Most Eminent and Reverend Lord Cardinals, Inquisitors-General against heretical depravity throughout the entire Christian commonwealth, having before my eyes and touching with my hands, the Holy Gospels, swear that I have always believed, do believe, and by God's help will in  the future believe, all that is held, preached, and taught by the Holy Catholic and Apostolic Church. But whereas -- after an injunction had been judicially intimated to me by this Holy Office, to the effect that I must altogether abandon the false opinion that the sun is the center of the world and immovable, and that the earth is not the center of the world, and moves, and that I must not hold, defend, or teach in any way whatsoever, verbally or in writing, the said false doctrine, and after it had been notified to me that the said doctrine was contrary to Holy Scripture -- I wrote and printed a book in which I discuss this new doctrine already condemned, and adduce arguments of great cogency in its favor, without presenting any solution of these, and for this reason I have been pronounced by the Holy Office to be vehemently suspected of heresy, that is to say, of having held and believed that the Sun is the center of the world and immovable, and that the earth is not the center and moves: 

96. Galileo’s Abjuration before the Inquisition, 1633
…because I have been enjoined, by this Holy Office, altogether to abandon the false opinion which maintains that the sun is the center and immovable, and forbidden to hold, defend, or teach, the said false doctrine in any manner… therefore, with a sincere heart and unfeigned faith, I abjure, curse, and detest the said errors and heresies, and generally every other error and sect contrary to the said Holy Church; and I swear that I will never more in future say, or assert anything, verbally nor in writing, which may give rise to a similar suspicion of me; but that if I shall know any heretic, or any one suspected of heresy, I will denounce him to this Holy Office, or to the Inquisitor and Ordinary of the place in which I may be.                                                   

97. Galileo’s sketch of the moon as seen from his telescope
A photograph of the moon
Here are a couple of pictures of the moon.
The first is Galileo’s sketch…{READ}
The second is a modern photograph…{READ}
So Galileo could see that the moon is not some ideal heavenly disk, but a real material sphere with craters and mountains. It was like another little world. However, as was often the case with Galileo, many philosophers did not want to accept his new knowledge. They just couldn’t bring themselves to admit that their whole world view was based on errors.
In a letter to Kepler, Galileo wrote… “{READ the quote}
“What do you think of the foremost philosophers of this university? In spite of my oft repeated efforts and invitations, they have refused, with the obstinacy of a glutted adder, to look at the planets or Moon or my telescope.” (letter to Kepler)
7/14/06
ISP A

98. Galileo Scenes from the Trial of Galileo Replica of Galileo’s
Telescope
Scenes from the Trial of Galileo

100. These ideas could be dangerous.
Galileo made many specific discoveries in astronomy, through observations by telescope.
The general implications…
● The planets are objects like the Earth – masses – rather than some kind of special heavenly objects. Or, to put it another way, the Earth is just another planet.
● The planets, including Earth, travel around the sun.
● The Universe is a lot bigger than we can see by the naked eyeeye.
{READ first line}
Galileo also asked what his discoveries would imply about the universe in general.
The general implications of his discoveries were significant evidence for the Copernican Model.
{READ the rest}
These ideas could be dangerous.
7/14/06
ISP A

101. Questions Raised by Galielo
Galileo’s conflict with the Church: Can questions about the natural world be settled by the Bible?
Or must they be settled by the best empirical and mathematical methods of science?
Are we free to investigate nature, or must we be constrained by religious authority?
The book of God: The history of God and his creation, written in a language for general human comprehension
The book of Nature: The natural world itself, revealing its laws in the phenomena--
--but written in the language of mathematics.

102. Galileo on science and Scripture:
I think it would be the part of wisdom not to allow any one to apply passages of Scripture in such a way as to force them to support as true any conclusions concerning nature, the contrary of which may afterwards be revealed by the evidence of our senses, or by actual demonstration. Who will set bounds to man's understanding ? Who can assure us that every thing that can be known in the world is known already ?

103. Galileo on science and Scripture (continued)
. . . I am inclined to think that Holy Scripture is intended to convince men of those truths which are necessary for their salvation, and which being far above man's understanding cannot be made credible by any learning, or by any other means than revelation. But that the same God who has endowed us with senses, reason, and understanding, does not permit us to use them, and desires to acquaint us in another way with such knowledge as we are in a position to acquire for ourselves by means of those faculties— that, it seems to me I am not bound to believe…

104. Galileo’s Genius Careful observation of a phenomenon
Deriving conclusions from “data”
Making new predictions
Publishing results “for everyone” [in Italian]
Anticipates his opponents arguments, and nullifies them by using stringent logic

105. Galileo’s Genius – Applied to Sunspots
Careful observation of a phenomenon
Observes sunspots (as did others before him)
Follows them over several weeks
Deriving conclusions from “data”
Concludes that these are things very close to the Sun’s surface
Making new predictions
Deduces that the sun rotates around itself in 26 days
Makes a prediction as to the Sun’s rotational axis
Publishing results “for everyone” [in Italian]
“Letters on Sunspots” (1612)
Anticipates his opponents arguments, and nullifies them by using stringent logic
Shows that sunspots can’t be inner planets

106. Saturn
Sketch of 1616
Engraving in “The Assayer” (1623)

107. F = ma = G Mm/r2 (m cancels out)
Applications
From the distance r between two bodies and the gravitational acceleration a of one of the bodies, we can compute the mass M of the other
F = ma = G Mm/r2 (m cancels out)
From the weight of objects (i.e., the force of gravity) near the surface of the Earth, and known radius of Earth RE = 6.4103 km, we find ME = 61024 kg
Your weight on another planet is F = m  GM/r2
E.g., on the Moon your weight would be 1/6 of what it is on Earth

108. Applications (cont’d)
The mass of the Sun can be deduced from the orbital velocity of the planets: MS = rOrbitvOrbit2/G = 21030 kg
actually, Sun and planets orbit their common center of mass
Orbital mechanics. A body in an elliptical orbit cannot escape the mass it's orbiting unless something increases its velocity to a certain value called the escape velocity
Escape velocity from Earth's surface is about 25,000 mph (7 mi/sec)
During the course of the quarter we'll see that these two methods have been applied over and over again to determine the masses of celestial bodies.

109. Objections to the Heliocentric Model Answered
If the Earth is moving, why do dropped objects appear to fall straight down?
Dropped objects start with the velocity of Earth (Galileo)
If the Earth rotates, why don't we get thrown off?
Earth's rotation isn't fast enough!
If the Earth revolves around the Sun, why don't we observe stellar parallax?
It's there, but very small, because the stars are so far away (Aristarchus)
Why don't we feel the wind of our motion?
The air moves along with the Earth

110. In 1992, the Roman Catholic Church finally repealed the ruling of the Inquisition against Galileo. The Church gave a pardon to Galileo and admitted that the heliocentric theory was correct. This pardon came 350 years after Galileo's death.

111. The observed solar system at the time of Newton
Sun
Mercury
Venus
Earth
Mars
Jupiter
Saturn
This was the solar system known at the time of Newton.
[[Clyde Tombaugh; b. Illinois 1906; grew up on a farm in Kansas; astronomer in New Mexico.]]
(all except Earth are named after Roman gods, because astrology was practiced in ancient Rome)
Three outer planets discovered later…
Uranus (1781, Wm Herschel)
Neptune (1846 Adams; LeVerrier)
Pluto (1930, Tombaugh)
7/14/06
ISP A

112. F a = m r m Gm F = 1 2 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: m F a =
The laws of motion
The theory of universal gravitation
Calculus, a new branch of mathematics 2 1 r m Gm F =
{READ to quotation}
Newton based his work on the discoveries of his predecessors. This Newton quotation is taken from a letter to Robert Hooke, another physicist of the time of Newton. {READ quotation}
“If I have been able to see farther than others it is because I stood on the shoulders of giants.”
--- Newton’s letter to Robert Hooke,
perhaps referring to Galileo and Kepler
7/14/06
ISP A

113. Newton’s Theory of Universal Gravitation
Newton and the Apple
Newton asked good questions  the key to his success.
Observing Earth’s gravity acting on an apple, and seeing the moon, Newton asked whether the Earth’s gravity extends as far as the moon.
{READ}
(The apple never fell on his head, but sometimes a stupid person will say that, trying to be funny.)
7/14/06
ISP A

114. William Herschel: 1782 and Caroline Herschel: 1750 – 1848AD
His sister, Caroline, helped her brother make the lenses for telescopes and kept his daily records.
She went on to discover seven comets and to list all the main stars. This became a vital source of information for astronomers.
She was awarded many medals by the Royal Astronomical Society and the King of Prussia
Became Britain’s top astronomer
Discovered the planet Uranus
Found many types of new stars and comets
1783: Found a new type of light called infrared

115. William and Caroline