Nikhil Mogalapalli

Choice 1 for TIC-TAC-TOE Project.

Physical Science: Block 4

Geocentric Theory

• One of the theories that has changed over the last 500 years is called the Geocentric Theory. At the end there is going to be an jeopardy game and the questions in Jeopardy are going to be about Geocentric Theory.

• So read the information carefully and try to answer all the questions in the jeopardy

Geocentric Theory

• The geocentric theory is the theory in astronomy states that the Earth is in the center of the universe and other planets, objects, and even the sun revolves around Earth.

• This theory was discovered in ancient Greece supported by Aristotle, Ptolemy, and most Greek philosophers.

• The Geocentric Theory was held in the early modern age and replaced by heliocentric theory by the time of 16th century by Copernicus, Galileo, and Kelper.

Geocentric Theory

• Two common observations were believed by philosophers to say that the Earth is in the center of the universe.

• The first is stars appear to revolve around Earth everyday, with stars circling around the poles rise then set and again it starts circling the poles.

• The second is common sense that the Earth is stationary and stable and is at rest.

Geocentric Theory

• The geocentric model was combined with a spherical Earth by philosophers of Ancient Greek and Medieval times.

• They are not saying that the Earth is flat like in the mythology, but saying that the motions of the planets were circular and not elliptical.

• The below picture is an illustration of Ptolemaic geocentric system by Portuguese cosmographers and cartographers Bartolomeu Velho.

Geocentric Theory

• Ptolemaic System

• In this theory each planet is moved by 5 or more spheres. One sphere is called a deferent that was a circle centered around a point halfway between the equant and the Earth. Another sphere is called the epicycle which is embedded in the deferent .

• The deferent revolves around the Earth while the epicycle revolves with the deferent causing the planets to move closer and farther from Earth at the point of its orbit.

• The epicycles of Venus and Mercury are always centered on the line between the sun and the Earth.

Geocentric Theory

• There is also an different order of planets in the Ptolemaic Theory. The order of the planets in outward position after the Earth.

• Moon

• Mercury

• Venus

• Sun

• Mars

• Jupiter

• Saturn

• Fixed Stars

• Sphere of Prime Sphere.

Geocentric Theory

• The picture below shows the basic elements of Ptolemaic astronomy showing an planet on an epicycle with an eccentric deferent and an equant point.

Geocentric Theory

• All the Greeks did not believe in the Geocentric system there were people who were called Pythagoreans said that the Earth was one of the planets revolving around some fire that we now call the sun.

• Some Pythagoreans like Hicetas and Ecphantus of 5th century B.C and Heraclides Ponticus in 4th century B.C believed that Earth rotated on its axis, but was still in the center of the universe.

Geocentric Theory

• The drawing below is from an Icelandic manuscript dated around 1750 illustrates the geocentric model.

Geocentric Theory

• The Copernican System

• In 1543 there was an system called Heliocentric System which was bought up by Copernicus which posited that the Earth and other planets revolved around the sun.

• This model was not so popular because Copernicus could not give better predictions that the Geocentric System.

• With the invention of the telescope in 1609 Galileo observed the phases of the Venus showed all its faces like the moon.

Geocentric Theory

• Galileo thought that if Venus is between Sun and Earth then its phases must be crescent or all dark.

• If Venus is beyond the sun, it must be gibbous or full.

• The below picture are the phases of the Venus

Geocentric Theory

• Johannes Kelper was the first astronomer to prove that the transit of the planet Venus in for the year 1631.

• Isaac Newton devised his law of gravitation which introduced gravitation as the force both kept the Earth and planets moving through the heavens and also kept the air from flying away.

• Friedrich Wilhelm Bessel successfully parallax of the star 61 Cygni, disproving the Ptolemy's assertion that parallax motion did not exist.

Geocentric Theory

• Hope you all are ready for the Jeopardy game coming up next.

• If you are not ready take 5 minutes recollect what you read.

• Good Luck in the Jeopardy!!!

Geocentric TheoryJeopardy

Rival Systems

Ptolemaic

System

Gravitation Copernican

System

Introduction

to

Geocentric

Theory

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Source

• "Geocentric Model." Wikipedia. 11 Sep 2008

<http://en.wikipedia.org/wiki/Geocentric>.

• Who were the People that believed the Earth to be one of the several planets that revolve around a central fire?

• Who was the Pythagorean who believed that Earth rotated at its axis, but remained at the center of the universe?

• What is the name given to the theory of the Pythagoreans?

• What was the theory called if it said the Earth was one of the planets that revolved around the sun?

• What was the theory called if it said the Earth was one of the planets that revolved around the sun?

• Which century did Heraclides Ponticus belong to?

• How many spheres moved each planet?

• What is a deferent?

• What is the sphere embedded in the deferent?

• The epicycles of what planets are centered on the line between the sun and Earth?

• What is the order of the spheres outward of Earth?

• Who constructed his three laws based on the heliocentric theory where the planets moved in elliptical orbit?

• In which years did Johannes Kelper construct his three laws?

• Which star’s parallax did Friedrich Wilhelm Bessel measure?

• In which year did Isaac Newton devise his universal law of gravitation?

• When did Galileo invent telescope?

• Who invented the telescope?

• When did Galileo use his telescope to find that Venus showed all its faces?

• Who saw all the phases of Venus?

• If Venus is between the sun and the Earth then the phase of Venus is what?

• Galileo observed that Venus showed all phases just as the what?

• Why was the Geocentric System held for many years after the introduction of the Copernican System?

• In which country did the Geocentric System was believed?

• In which century Geocentric System was replaced by Heliocentric System?

• Why did not people agree with the Heliocentric Theory?

• Who were the two people who most supported the Geocentric Theory?

• What was the difference between the Geocentric Theory and the theory of some mythology?

• Heliocentric Theory

• Geocentric Theory

• Pythagoreans

• Hicetas, Ecphantus or Heraclides Ponticus

• 4th century B.C.

• Epicycle

• 5 spheres

• the deferent was a circle centered around a point halfway between the equant and the earth

• Venus and Mercury

• Moon • Mercury • Venus • Sun • Mars • Jupiter • Saturn • Fixed Stars • Sphere of Prime Mover

• 1687

• 1609

• Johannes Kelper

• 1609 and 1619

• 61 Cygni

• Galileo

• 1610

• Galileo

• Crescent or all dark

• Gibbous or Full

• Ancient Greece

• 16th century B.C

• because they did not have so many evidences

• Ptolemy and Aristotle

• The difference is the mythology believed that the Earth was flat and the Geocentric theory does not say the Earth is flat.