The Geocentric Theory The Geocentric Theory vs. The Heliocentric vs. The Heliocentric

TheoryTheory

The Geocentric TheoryThe Geocentric Theory

•The The earthearth is is located at the located at the center of the center of the universeuniverse and and all the planets all the planets revolve revolve around the around the earth. earth.

Geocentric Cont…..Geocentric Cont…..•The Geocentric theory was believed by The Geocentric theory was believed by

the Catholic church especially because the Catholic church especially because the church taught that God put the church taught that God put earthearth as the center of the universe which as the center of the universe which made earth special and powerful. made earth special and powerful.

•The idea of the Earth actually The idea of the Earth actually movingmoving was widely felt as a foolish suggestion was widely felt as a foolish suggestion because, as they saw it, if the Earth because, as they saw it, if the Earth was moving they would be able to feel was moving they would be able to feel it. it.

Aristotle (384-322 B.C.)Aristotle (384-322 B.C.)• Developed an early model Developed an early model

based on the concept of based on the concept of uniform uniform circularcircular motion. He motion. He placed the earth at the placed the earth at the center of the universe and center of the universe and all of the planets, sun and all of the planets, sun and stars around it. stars around it.

• When Aristotle lived, if a When Aristotle lived, if a person could person could “reason”“reason” out out why something happened, why something happened, then you didn’t need to do then you didn’t need to do any experiments to see any experiments to see what would happen.what would happen.

• In the realm of change, the In the realm of change, the natural motion of earthy natural motion of earthy materials was to seek the materials was to seek the center of the universe. center of the universe.

•This is why Aristotle placed This is why Aristotle placed the earth at the center of the earth at the center of the cosmos. This is also his the cosmos. This is also his explanation for why objects explanation for why objects fall when dropped. A fall when dropped. A dropped object is just dropped object is just following its natural following its natural tendency to seek the center tendency to seek the center of the universe. of the universe.

•Aristotle reasoned that if the earth Aristotle reasoned that if the earth rotated about its axis, we should rotated about its axis, we should fly fly offoff into space. Since we don't, the into space. Since we don't, the earth must be stationary.earth must be stationary.

• It would be almost 1900 years before It would be almost 1900 years before Galileo introduced the concepts of Galileo introduced the concepts of gravity and inertiagravity and inertia that explain why that explain why these effects are not observed even these effects are not observed even though the earth does move. though the earth does move.

Ptolemy (140 A.D.)Ptolemy (140 A.D.)

•PtolemyPtolemy advanced advanced the geocentric the geocentric theory in a form theory in a form that prevailed for that prevailed for 1400 years1400 years..

•He added He added mathematics to mathematics to support the theorysupport the theory

Ptolemy’s ProblemPtolemy’s Problem

•Many supporters of the Many supporters of the geocentric theory had geocentric theory had one piece of evidence one piece of evidence they couldn’t explain – they couldn’t explain – the movement of MARS.the movement of MARS.

•Let’s take a break and Let’s take a break and investigate this investigate this movement.movement.

Mars’ MotionMars’ Motion

http://csep10.phys.utk.edu/astr161/lect/retrograde/retrograde.html

How did Ptolemy Explain How did Ptolemy Explain this Problem?this Problem?

•Ptolemy used geometric models to Ptolemy used geometric models to predict the positions of the sun, moon, predict the positions of the sun, moon, and planets, using combinations of and planets, using combinations of circular motion known as circular motion known as epicyclesepicycles. .

•An epicycle is an orbit within an orbitAn epicycle is an orbit within an orbit•Having set up this model, Ptolemy Having set up this model, Ptolemy

then went on to describe the then went on to describe the mathematics which he needed in the mathematics which he needed in the rest of the work.rest of the work.

Ptolemy’Ptolemy’s Model s Model

– – EpicycleEpicycle

s s IncludedIncluded

The Heliocentric TheoryThe Heliocentric Theory

•The Sun is the center of our The Sun is the center of our solar solar systemsystem

Copernicus (1473-1543)Copernicus (1473-1543)• Polish astronomer who Polish astronomer who

advanced the theory that advanced the theory that the Earth and other the Earth and other planets revolve around planets revolve around the Sun. This was highly the Sun. This was highly controversial at the time. controversial at the time.

• The Ptolemaic model had The Ptolemaic model had been widely accepted in been widely accepted in Europe for 1000 years Europe for 1000 years when Copernicus when Copernicus proposed his model. proposed his model.

http://alpha.lasalle.edu/~smithsc/Astronomy/retrograd.html

•Copernicus was told by many scholars that Copernicus was told by many scholars that he should make his new findings he should make his new findings accessible to others by publishing it. In accessible to others by publishing it. In 1543 the book called "On the revolutions 1543 the book called "On the revolutions of the heavenly bodies" was released. of the heavenly bodies" was released. Copernicus's book had a great impact that Copernicus's book had a great impact that angered the Catholic and Protestant angered the Catholic and Protestant Church. Church.

•The Church became so angry – the The Church became so angry – the Geocentric theory made human beings Geocentric theory made human beings seem closer to God and since earth was in seem closer to God and since earth was in the center that meant humans were more the center that meant humans were more special. The heliocentric theory special. The heliocentric theory changed changed that perspective completely, making that perspective completely, making humans lose that position in the universe.humans lose that position in the universe.

Galileo (1564-1642)Galileo (1564-1642)•An Italian scientist, An Italian scientist,

Galileo was renowned for Galileo was renowned for his contributions to his contributions to physics, astronomy, and physics, astronomy, and scientific philosophy. He scientific philosophy. He is regarded as the chief is regarded as the chief founder of founder of modern modern science. science.

•Galileo was condemned Galileo was condemned by the Catholic Church by the Catholic Church for his view of the for his view of the cosmos based on the cosmos based on the theory of Copernicus.theory of Copernicus.

Galileo’s BooksGalileo’s Books• Galileo published his discoveries and Galileo published his discoveries and

support for the Copernican model in two support for the Copernican model in two books published in 1616 and 1632. books published in 1616 and 1632.

• Galileo was unusual for the time because he Galileo was unusual for the time because he wrote in Italian rather than Latin like most wrote in Italian rather than Latin like most scholars.scholars.

• Galileo also took great pains to make his Galileo also took great pains to make his books interesting often writing them in the books interesting often writing them in the form of dialogues rather than dry, boring form of dialogues rather than dry, boring dissertations. dissertations.

• After his first book, After his first book, "Starry Messenger""Starry Messenger", was , was published he was warned by the Church not published he was warned by the Church not to publicly support Copernicism again. to publicly support Copernicism again.

Trial Before the InquisitionTrial Before the Inquisition

• Galileo abided by this edict until 1632 Galileo abided by this edict until 1632 when he published when he published "A Dialogue on the Two "A Dialogue on the Two Chief World Systems"Chief World Systems". This book's outright . This book's outright support for the Copernican model and its support for the Copernican model and its ridiculing of the Ptolemaic model earned ridiculing of the Ptolemaic model earned Galileo a trial before the Galileo a trial before the InquisitionInquisition. .

• Galileo was accused of heresy and Galileo was accused of heresy and sentenced to house arrest for life. sentenced to house arrest for life. However, he got off easily compared to However, he got off easily compared to fellow Italian fellow Italian Giordano BrunoGiordano Bruno who was who was burned at the stake in 1600 for teaching burned at the stake in 1600 for teaching Copernican ideas. Copernican ideas.

• In In 19921992, the Roman , the Roman Catholic Church finally Catholic Church finally repealed the ruling of repealed the ruling of the Inquisition against the Inquisition against Galileo. The Church gave Galileo. The Church gave a pardon to Galileo and a pardon to Galileo and admitted that the admitted that the heliocentric theory was heliocentric theory was correct. This pardon correct. This pardon came 350 years after came 350 years after Galileo's death.Galileo's death.