History of Astronomy and Cosmology
Ancients
Babylonians were the first people to observe the sky with accuracy. They predicted eclipses and comets and put pictures in the skies but put forward no theory of the earths place in space.
Greek philosophers began to think about the place of man and Earth in the universe. The prevailing early opinion of the Greeks was that the Earth floated in the sea with air above and Hades (The underworld) below. Surrounding this was Aether.
The Pythagoreans (Pythagoras and his students) developed a system where the Earth was one of the objects surrounding the 'Hearth of the universe'. More on Pythagoreans
The counter-earth provided symmetry and was a theory that continued on some level until the the advent of space travel when we could finally see that there was no object on the other side of the Sun.
Note that this is essentially a Geocentric universe (earth centered) with the sun orbiting the Earth and the hearth. This was the usual view of the Greeks, but was challenged by Aristarchus of Samos who didn't believe that the massive sun would orbit such a small object like Earth. He came up with the first Heliocentric ( Sun centered) universe. Unfortunately for him, this was rejected by the rest of the Greek philosophers. The arguments against the Earth orbiting the Sun included the idea that if the Earth was moving through space, why don't we feel a wind from the movement and why doesn't an object thrown upwards get left behind as the earth moves. These questions would only be resolved with the concepts of inertia and gravity formulated some 17 centuries in the future.
The most famous of the Greek Cosmologists was Ptolemy. He was born in Alexandria, Egypt in 100 AD and worked on his cosmology following on from ideas put forward by Aristotle and Hipparchus. He formulated a cosmology to explain the motions of the planets using a very complicated system of cycles within circles known as epicycles that was more accurate than simple circular orbits. LINK It explained the retrograde (backward) motion observed for Mars that had perplexed generations of philosophers. More on Ptolemy
This view lasted for 1400 years. The following years produced very little in the way of cosmological theory. A major underlying reason for this is that the climate of the time was heavily religious, this was the main period of power for the Catholic church and the view of the universe provided by Ptolemy fitted nicely into the Orthodoxy of this period. That the universe revolved around the Earth proved the uniqueness of the Earth and that God had made this planet special.
Renaissance
It wasn't until the 16th Century that the accepted views began to be challenged. It was a difficult period for any scientists who thought to go against the church's accepted theories, as the inquisition was at the height of its power and there were several scientists executed for their new ideas.
As such, the most famous step forward in Cosmology took place in the mind of one man and was hidden from the authorities until the time of his death.
Nicolas Copernicus published his De Revolutionibus Orbium Coelestium in 1543 at the end of his life. He had kept back this work for fear of being branded a heretic. In it he described a system of the universe in which the Earth was not at the center, but followed an orbit around the Sun along with the other planets. The different speeds of the planets were explained by the different distances from the Sun. The theory was not completely removed from the earlier Greeks ideas, for example, the orbits of the planets were still circular and the stars were still fixed to the outermost celestial sphere. He did answer some of the problems of the greek theories such as saying that an object thrown upwards is not left behind, because it 'carries' the same velocity as Earth and therefore continues on with the Earth. This is an early representation of Newton's 1st law. More on Copernicus
Despite some problems, the theory gradually became accepted having been built upon by Giordano Bruno (executed by the Inquisition for his ideas) and others. The fact that the church was so opposed to the theory helped it gain notoriety in scientific circles and eventually became the theory to base new ideas upon.
The next few decades saw several astronomical advances as techniques and instrumentation improved. Tycho Brahe was influential in developing rigorous observations, and while he himself was positive about the truth of the Catholic version of cosmology, he put a nail into the coffin of his own beliefs. In 1572, he observed a new object in the heavens. What we now know as a supernova had occurred in the constellation of Cassiopeia. This was shocking as the traditional views held that the universe was unchanging, yet here was something completely new. On the evidence of his observations, Brahe concluded that the new star must be very far away as it was not affected by parallax as the earth moved.
A further nail in the coffin of the Accepted doctrine was given by Galileo Galilei in the early 1600s. Using a new piece of equipment, the telescope, he discovered that Jupiter was orbited by some small objects. This showed that the Earth was not special because there were objects in the universe that did not revolve around it.
The new advances of the renaissance did not prevent some following of antiquated theories. Johannes Kepler in the late 16th century was trying to place the planets into a system that would prove the truth of Aristotle and other Greek views of the universe. He thought that the universe was based around numbers and that the planets could be arranged so that they followed a pattern of geometric shapes. Having spent many years on this, he eventually concluded that this could not be done and turned his attention to working through some of Tycho Brahe's observations. It was these observations that led to him developing the laws which made him famous. These laws described the orbits of the planets using ellipses rather than circles which were favoured up to this point. This is a link to a good page with some animated diagrams.
The most well known contribution to Cosmology before modern times came in 1687 with the publication of Newton's Philosophia Naturalis Principia Mathematica (Principia for short). In this massively influential work, Newton described a theory for the workings of the universe based on a mathematical appreciation of Gravity.
