FEATURE: A short history of astronomy.

Early Man

There is little recorded information on early man’s impressions and ideas about the sky’s.  We have some cave panting’s such as those discovered in the Lascaux caves, dated to around 15,280 B.C. that seem to depict the summer triangle.  There are other drawings of eclipses comets and supernova such as the Pueblo petrogath, early man probably held the heavens in reverence and fear, believing that the stars held power over earthly existence.

England 2000 B.C	Construction of stone hedge begins in 2600 B.C and was finally completed in 2000 B.C; essentially it was built to be a computer of sorts for calculating the positions of the planets and the sun.
Babylonians 1600 B.C	The Babylonian’s where the first to keep Written records of astronomical observations.  They recorded the positions of planets and the times of eclipses.

 

Hellenistic culture.

“Philosophy is the science which considers truth.”

Aristotle

The ancient Greeks inherited astronomical records from the Babylonians, this then was applied to construct a cosmological framework, which was used for navigation and to think of new experiments. The end of this period was when the library at alexander burns, Rome falls and humanity enters its dark age.  Little is known about what discovery’s where made during this time.  But the loss of the millions of books at the library at alexander was a blow to mankind’s knowledge.
 

Thales 624 B.C – 546 B.C	Used the information from the Babylonians to predict eclipses. Thales rejection of mythological explanations became an essential idea for the scientific revolution.
Aristotle 384 B.C – 322 B.C	Aristotle presented a model of the universe in which the distant stars and planets execute perfectly circular motions.
Heraclites 397 B.C – 312 B.C	Developed the first solar system model and began the geocentric vs heliocentric debate. In the geocentric models of the solar system all of the planets have perfectly circular orbits.
Aristarchus 310 B.C – 230 B.C	Developed Heliocentric theory, when it was first proposed heliocentric theory was not universally accepted, it flew in the face of everything that classical society thought it knew about the way the universe works.   A few philosophical problem that the theory faced where: ·         If the earth is in motion, why can’t we feel it? ·         No Parallax seen in the stars ·         Geocentric ‘felt’ right, it put mankind at the very centre of everything
Eratosthenes 276 B.C – 194 B.C	The early Greeks where able to work out that the earth was a sphere, by studying the shadow of the moon during Luna eclipses. Eratosthenes, nick named beta by his contemporise (as in second best at everything) took this a step further and used this information to help him work out the circumference of the earth.  He knew that a stick placed in the ground at a certain time in Syene, on a particular day cast no shadow.  He also knew that if you placed a stick in the ground at the same time at Alexandria it had cast a shadow at 7°; lastly he hired a man to pace out the distance between the two city’s (4900 stadia).  Given that information, Eratosthenes was able to work out, almost exactly, the circumference of the earth.
Hipparchus 190 B.C – 120 B.C	Produced the first star catalogue and recorded the names of the constellations, recording the position of at least 850 stars.
Babylonian astronomers 164 B.C	First recorded sighting of halyes comet.
Ptolemy 90 -168 A.D	Liberian of the university of Alexandria. He combined geocentric theory with hundreds of records containing as much planetary data as he had available to him, using this he was able to formulate a complete mathematical description of the solar system. Ptolemy came to the realisation that the planets where much closer than the stars, however he also believed on crystalline spheres that he thought where tethered to the heavenly bodies, the resulting model of the solar system had 28 epicycles to account for the motion.  This began the first mathematical paradigm for understanding nature.
China 1054 A.D	Astronomers in China are the first to record the crab nebula who noted it as a guest star.  This has also been recorded in rock painting by the native amreicans.
Ulugh Beg 1394-1449	Bulit a three story observatory, the observatory produced astronomical tables conataion 1000 stars, perhaps the most important astronomer of the 15th century.

 

The Renaissance

“Philosophy is written in that great book which ever is before our eyes – I mean the universe – but we cannot understand it if we do not first learn the language and grasp the symbols in which it is written. The book is written in mathematical language and the symbols are triangles, circles and other geometrical figures, without whose help it is impossible to comprehend a single word of it; without which one wanders in vain through a dark labyrinth.”

Galileo Galilee

Nicolas Copernicus 1473-1543	Copernicus challenged the established doctrine of an earth centric universe.  This went much deeper than solving retrograde motion in fact it was seen as tantamount to heresy as a number of biblical passages seem to indicate a geocentric universe. Copernicus challenged and brought about change, a paradigm shift that ushered in the scientific revolution.  However circular orbits where still present in his new model of the universe, as where the epicycles of Ptolemy, in fact his model called for more.  Copernicus model would have failed Occam’s Razor, that a scientific model should be as simple as possible.
Tycho Brahe 1546 – 1601	Tycho Brahe used sextants (Telescpoes had not been invented yet) to build a observatory in his natavie Denmark.  He used relatively simple equipment to measure the position of the stars and planets to a very high dgree of accuracy.  This information constituted the first modern database.  Brahe was able to prove for the first time, using triganomitry, that the sun was much father from the sun  than the moon was from the earth.  In 1572 Brahe discovered a supernova in the consterlation of Cassiopeia.
Johann Bayer 1572-1625	Made a complete caterlouge of all the stars, allocateing a letter of the greek alphabet to each with Alpha being the brightest.  It has gone under many revisions but we still use ‘Bayer designations’ to this day.
Johannes Kepler 1571-1630	Used the database formulated by Brahe to formulate the laws of planetary motion, these laws resolved the problems of epicycles in heliocentric thory by using elipses in place of circles  for planetary orbits.  This was the origin of the clock work universe concept  and marked another paragdim shift in the philosophy of science .   Keplers laws.   1)       Planetary orbits are elliptical with the sun at of the two foci 2)       A planet sweeps out in equal areas in equal times as it orbits the sun 3)       The square of the period of any planet is proportional to the cube of the semimajor axis of its orbit.
Galileo Galilei 1564 – 1642	Galileo with a tiny telescope, no more powerful than a entry level pair of modern binoculars (a 3x refracting) proved that the universe did not conform to perfict orbits, and also proved that the universe was not geo centric.  Alogth he was the first to use a telescope for the purpous of astronomy he was not the inventor of the device, it was invented a year before by Hans Lipperhey, a German spectacle maker.  He did however build his own telescope.  Other descoverys by Galileo where:   o    Sun spots o    Mountains and ‘seas’ on the moon o    Our galaxy is made of many thousands of stars o    Venus has phases o    The moons of Jupiter (still called the jovian moons) Io, Europa, callisto and Ganymead.
Isaac Newton 1643-1727	Developed the law of universal gravitation, accelerated motion. Invented calculus and the first reflecting telescope the basis of which is still used to this day.
Heninrich Wilhelm Matthias Olbers 1758-1840	In 1826 Olbers formulated a paradox that seemed to call newtons modle of the universe into question. Thew paradox states that the universe can not be infimnate and eternal. Essentulay the paradox gose:   Why is the night sky dark? In an infinite and unchangeing universe every line of sight should from an observer should hit a star, as in a forist where all lines of sight hit a tree

Modern Era

“If you wish to make an apple pie from scratch, you must first invent the universe.” 

Carl Sagen

Edwin Hubble 1889 - 1953	Edwin Hubble; using a 100” telescope, at that time the largest in the world, proved that country to current ideology the milky way was not the only galaxy in the universe.   In 1929 he published finding that led to our understanding that the universe was expanding.
1957 Russia	Sputnik, a name that translates to “Fellow traveller of Earth” is launched and becomes the first manmade object to leave earths atmosphere
1959 Russia	The probe “first cosmic ship” later to be renamed ‘Luna I’ launched and despite missing its mark becomes the first manmade object to come close to the moon.  Originally meant to impact with the Luna surface due to an issue with ground control it instead flew by the moon at 5,900km at its closest point.
1961 Russia	Yuri Gagarin becomes the first man in space his craft, Vostok I, carries him on a 108 minute flight.
1969 The moon	Buzz Aldrin and Nile Armstrong become the first men to walk on the moons
1990 USA	The Hubble space telescope launched and is still in use today.  The images sent back have been as awe inspiring as they have been scientifically important.

 

 

FEATURE: Heliocentrism

 Heliocentrism
 

Finally we shall place the sun himself at the centre of the universe

Nicolaus Copernicus

 

It is surely harmful to souls to make it a heresy to believe what is proved

Galileo Galilei

Since as far back as 270bc it has been posited that the sun is in the centre of the solar system.  The idea didn’t catch on until the 17^th century when a complete heliocentric theory emerged. At the time the church had a lot more influence and since the bible seems to point to a geocentric model that is what the prevailing theory was.  Heliocentrism shattered our world view mankind was no longer literally the centre of the universe.

                In antiquity models of the cosmos placed earth at the centre with everything radiating outward from there, the orbits executed perfect circles. Philosophers were attracted to the idea that nature favoured perfect geometries as more accurate measurements where made there clockwork mathematical descriptions increasingly failed to explain them.  It wasn’t until Kepler that these perfect circles where replaced by the more correct ellipses. The ancient Greeks believed that all the heavenly bodies were affixed to crystal spheres that spun about the Earth causing the stars pinned upon them or revealed through tiny holes within them to circle the north and south celestial poles each night.

                The idea that the heavens revolve about the sun rather than the Earth a heliocentric model, after the Greek word helios for sun, was suggested by ancient Greek philosophers as far back as Aristarchus in 270bc who conveyed such ideas in his writings.  After calculating the relative sizes of the earth and the sun Aristarchus realized the sun was much larger it made more sense to him that the smaller earth would move rather than the larger Sun.

Ptolemy

                In the second century Ptolemy used mathematics to predict the motions of the stars and Planets.  He did so reasonably well but; there where patens that his equations could not match.  Most puzzling of all is that the planets seemed to change direction. Ptolemy believed , like many of his contemporises, that the planets literally turned on giant wheels in the sky.  He invented an explanation for the retrograde motion by adding extra cogs to their orbits. Theses superimposed epicycles gave the appliance of the planets occasionally looping backward.

Copernicus

                Born in Torun Poland Copernicus trained as a cannon taking classes in law, medicine, astronomy and astrology he was fascinated by but critical of Ptolemy’s ideas about the order of the universe.  Copernicus worked out his own system where the earth and the other planets rotate around the sun he published this theory in his work ‘On The Revolutions of Heavenly Spheres’ published just two months before he died. Ideas like this were occasionally mooted over the centuries but not taken seriously.  So it was not until the 16^th century that the consequences of the sun central model were fully developed.

The established church and society in general favoured Ptolemy’s geocentric view.

Galileo

Galileo Galilei notoriously challenged the roman catholic church by championing heliocentrism.  He backed up his audacity with careful observations made through the newly developed telescope.  Galileo found evidence that the earth was not central at all, that Jupiter has moons orbiting it and that Venus has phases like the moon.  He published these discoveries in his book starry messenger having made the audacious clame that the suns apparent migration across the sky was simply down to the earth’s rotation he found himself summoned to Rome. Despite the fact that Galileo’s observations where backed up by Jesuit astronomers the church refused to accept galilos theory.  Stating that although it was appealing in its simplicity that the theory could not be taken literally. Although restricted Galileo remained certain that his Sun cantered explanation was true, asked by Pope Urban VIII to write a balanced account of both sides in a ’dialogue of the two world systems’ Galileo upset the pontiff by expressing a bias for his own view over that of the church.  He was summoned back to Rome and put on trial for breaking his ban and placed on house arrest for the rest of his life.

Kepler

Meanwhile German astronomer Johannes Kepler was also working on the mathematics of planetary motions. Kepler published his analysis of the path of Mars in his 1609 book Astronomia nova.  Kepler found that an ellipse rather than a circle gave a better description of the red planets orbit around the sun.  now considered to be a basic law of physics Kepler’s vision was advanced for its time and took a long time to be accepted, Galileo for one took no notice.

Gradual acceptance

Evidence of the fact of heliocentric theory accumulated over the Century’s.  Kepler’s mechanics of orbits influenced Newton’s theory of gravity, as further planets were discovered, the fact that they orbited the sun was obvious. Man’s place at the centre of things is no longer tenable

270bc	Ancient Greeks propose sun centred model
200	Ptolemy adds epicycles to explained retrograde motions
1543	Copernicus publishes his heliocentric model
1609	Galileo discovers Jupiter’s moons.  Kepler models orbits as ellipses
1633	Galileo put on trial for teaching heliocentrism