Monday, May 3, 2010


"The great enemy of the truth is very often not the lie, deliberate, contrived and

dishonest, but the myth, persistent, persuasive and unrealistic."


F. Kennedy

In astronomy, the geocentric model or the Ptolemaic worldview of the universe is the

superseded theory that the Earth is the center of the universe and other objects go around it.

Belief in this system was common in ancient Greece. It was embraced by both Aristotle and

Ptolemy, and most, but not all, Ancient Greek philosophers assumed that the Sun, Moon,

stars, and naked eye planets circle the Earth. Similar ideas were held in ancient China.

Two common observations were believed to support the idea that the Earth is in the center of

the Universe: The first observation is that the stars, sun, and planets appear to revolve around

the Earth

each day,

with the stars


around the

pole and

those stars

nearer the

equator rising

and setting

each day and

circling back

to their rising

point. The

second is the




that as the

Earth is solid

and stable it

is not moving—but is at rest.

The geocentric model held sway into the early modern age; from the late 16th century

onward it was gradually replaced by the heliocentric model of Copernicus, Galileo and



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In astronomy,

heliocentrism is the

theory that the Sun is

stationary and at the

center of the

universe. The word

came from the Greek.


heliocentrism was

opposed to

geocentrism, which

placed the Earth at

the center. Though

discussions on the

possibility of

heliocentrism date to

classical antiquity, it

was not until 1,800

years later, however,

in the 16th century,

that the Polish

mathematician and

astronomer Nicolaus

Copernicus presented

a fully predictive mathematical model of a heliocentric system, which was later elaborated and

expanded by Johannes Kepler.


Nicolaus Copernicus

Nicolaus Copernicus (19 February 1473 – 24 May 1543) was the

first astronomer to formulate a comprehensive heliocentric

cosmology, which displaced the Earth from the center of the

universe. His epochal book, De revolutionibus orbium coelestium

(On the Revolutions of the Celestial Spheres), published in 1543

just before his death, is often regarded as the starting point of

modern astronomy and the defining epiphany that began the

scientific revolution. His heliocentric model, with the Sun at the

center of the universe, demonstrated that the observed motions of

celestial objects can be explained without putting Earth at rest in

the center of the universe. His work stimulated further scientific

investigations, becoming a landmark in the history of science that

is often referred to as the Copernican Revolution.


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Among the great polymaths of the Renaissance, Copernicus was a mathematician,

astronomer, physician, quadrilingual polyglot, classical scholar, translator, artist, Catholic

cleric, jurist, governor, military leader, diplomat and economist. Among his many

responsibilities, astronomy figured as little more than an avocation — yet it was in that field

that he made his mark upon the world.

Copernicus' major theory was published in De revolutionibus orbium coelestium (On the Revolutions

of the Celestial Spheres), in the year of his death, 1543, though he had formulated the theory several

decades earlier.

In his Commentarial, Copernicus had summarized his system based on the seven assumptions:

1. There is no one center of all the celestial circles or spheres.

2. The center of the earth is not the center of the universe, but only of gravity and of the lunar sphere.

3. All the spheres revolve about the sun as their midpoint,

and therefore the sun is the center of the


4. The ratio of the earth's distance from the sun to the height of the firmament (outermost celestial

sphere containing the stars) is so much smaller than the ratio of the earth's radius to its distance from

the sun that the distance from the earth to the sun is imperceptible in comparison with the height of

the firmament.

5. Whatever motion appears in the firmament arises not from any motion of the firmament, but from

the earth's motion. The earth together with its circumjacent elements performs a complete rotation on

its fixed poles in a daily motion, while the firmament and highest heaven abide unchanged.

6. What appear to us as motions of the sun arise not from its motion but from the motion of the earth

and our sphere, with which we revolve about the sun like any other planet. The earth has, then, more

than one motion.

7. The apparent retrograde and direct motion of the planets arises not from their motion but from the

earth's. The motion of the earth alone, therefore, suffices to explain so many apparent inequalities in

the heavens.

Johannes Kepler

Johannes Kepler (December 27, 1571 – November 15, 1630) was a German mathematician,

astronomer and astrologer, and key figure in the 17th century scientific revolution. He is best

known for his eponymous laws of planetary motion, codified by later astronomers based on

his works Astronomia nova, Harmonices Mundi, and Epitome of Copernican Astrononomy.

They also provided one of the foundations for Isaac Newton's theory of universal gravitation.

During his career, Kepler was a mathematics teacher at a seminary school in Graz, Austria,

an assistant to astronomer Tycho Brahe, the court mathematician to Emperor Rudolf II, a

mathematics teacher in Linz, Austria, and an adviser to General Wallenstein. He also did


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fundamental work in the field of optics, invented an

improved version of the refracting telescope (the

Keplerian Telescope), and helped to legitimize the

telescopic discoveries of his contemporary Galileo


Kepler lived in an era when there was no clear

distinction between astronomy and astrology, but

there was a strong division between astronomy (a

branch of mathematics within the liberal arts) and

physics (a branch of natural philosophy). Kepler also

incorporated religious arguments and reasoning into

his work, motivated by the religious conviction that

God had created the world according to an

intelligible plan that is accessible through the natural

light of reason. Kepler described his new astronomy

as "celestial physics", as "an excursion into

Aristotle's Metaphysics", and as "a supplement to

Aristotle's On the Heavens", transforming the

ancient tradition of physical cosmology by treating astronomy as part of a universal

mathematical physics .

Mysterium Cosmographicum

Johannes Kepler's first major astronomical work,

Mysterium Cosmographicum (The Cosmographic

Mystery), was the first published defense of the

Copernican system. Kepler claimed to have had

an epiphany on July 19, 1595, while teaching in

Graz, demonstrating the periodic conjunction of

Saturn and Jupiter in the zodiac; he realized that

regular polygons bound one inscribed and one

circumscribed circle at definite ratios, which, he

reasoned, might be the geometrical basis of the

universe. After failing to find a unique

arrangement of polygons that fit known

astronomical observations (even with extra

planets added to the system), Kepler began

experimenting with 3dimensional

polyhedra. He

found that each of the five Platonic solids could

be uniquely inscribed and circumscribed by

spherical orbs; nesting these solids, each encased in a sphere, within one another would

produce six layers, corresponding to the six known planets—Mercury, Venus, Earth, Mars,

Jupiter, and Saturn. By ordering the solids correctly—octahedron, icosahedron,


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dodecahedron, tetrahedron, cube—Kepler found that the spheres could be placed at intervals

corresponding (within the accuracy limits of available astronomical observations) to the

relative sizes of each planet's path, assuming the planets circle the Sun. Kepler also found a

formula relating the size of each planet's orb to the length of its orbital period: from inner to

outer planets, the ratio of increase in orbital period is twice the difference in orb radius.

However, Kepler later rejected this formula, because it was not precise enough.

Kepler thought he had revealed God's geometrical plan for the universe. Much of Kepler's

enthusiasm for the Copernican system stemmed from his theological convictions about the

connection between the physical and the spiritual; the universe itself was an image of God,

with the Sun corresponding to the Father, the stellar sphere to the Son, and the intervening

space between to the Holy Spirit. His first manuscript of Mysterium contained an extensive

chapter reconciling heliocentrism with biblical passages that seemed to support geocentrism.

With the support of his mentor Michael Maestlin, Kepler received permission from the

Tübingen university senate to publish his manuscript, pending removal of the Bible exegesis

and the addition of a simpler, more understandable description of the Copernican system as

well as Kepler's new ideas. Mysterium was published late in 1596, and Kepler received his

copies and began sending them to prominent astronomers and patrons early in 1597; it was

not widely read, but it established Kepler's reputation as a highly skilled astronomer. The

effusive dedication, to powerful patrons as well as to the men who controlled his position in

Graz, also provided a crucial doorway into the patronage system.

Though the details would be modified in light of his later work, Kepler never relinquished the

Platonist polyhedralspherist

cosmology of Mysterium Cosmographicum. His subsequent

main astronomical works were in some sense only further developments of it, concerned with

finding more precise inner and outer dimensions for the spheres by calculating the

eccentricities of the planetary orbits within it. In 1621 Kepler published an expanded second

edition of Mysterium, half as long again as the first, detailing in footnotes the corrections and

improvements he had achieved in the 25 years since its first publication.

Galileo Galilei

Galileo Galilei (15 February 1564 – 8 January 1642) was

an Italian physicist, mathematician, astronomer, and

philosopher who played a major role in the Scientific

Revolution. His achievements include improvements to the

telescope and consequent astronomical observations, and

support for Copernicanism. Galileo has been called the

"father of modern observational astronomy," the "father of

modern physics," the "father of science," and "the Father

of Modern Science." Stephen Hawking says, "Galileo,

perhaps more than any other single person, was

responsible for the birth of modern science."


The motion of uniformly accelerated objects, taught in nearly all high school and introductory

college physics courses, was studied by Galileo as the subject of kinematics. His

contributions to observational astronomy include the telescopic confirmation of the phases of

Venus, the discovery of the four largest satellites of Jupiter (named the Galilean moons in his

honour), and the observation and analysis of sunspots. Galileo also worked in applied science

and technology, improving compass design.

Galileo's championing of Copernicanism was controversial within his lifetime, when a large

majority of philosophers and astronomers still subscribed (at least outwardly) to the

geocentric view that the Earth is at the centre of the universe. After 1610, when he began

supporting heliocentrism publicly, he met with bitter opposition from some philosophers and

clerics, and two of the latter eventually denounced him to the Roman Inquisition early in

1615. Although he was cleared of any offence at that time, the Catholic Church nevertheless

condemned heliocentrism as "false and contrary to Scripture" in February 1616, and Galileo

was warned to abandon his support for it—which he promised to do. When he later defended

his views in his most famous work, Dialogue Concerning the Two Chief World Systems,

published in 1632, he was tried by the Inquisition, found "vehemently suspect of heresy,"

forced to recant, and spent the rest of his life under house arrest.

Galileo's contribution to astronomy are huge. He with his first practical telescope with a

resolution of over 30x saw what was till that time never seen by any human with naked eyes.

He also finally stated that earth isn't at the center of the universe and had to face the wrath of


Today even with so many advancements in the field of astronomy and space, one still can

never predict where we actually are in the universe. The sheer size of universe and its

vastness makes it impossible for us to precisely say anything. Hence where we are is only a

random guess.

" Myth is, after all, the neverending


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