The Early civilizations

Well, as early as 3000 BC the Babylonians began careful observations of the heavenly bodies and even produced calendars. Soon after the Ancient Egyptians actually catalogued the stars, as well as creating both calendars and clocks (sun dials) based on their observations of the heavens.

The Ancient Greeks

The first major work on the stars was not produced until around 600 BC when the Ancient Greeks founded the science of astronomy. It was Thales of Miletus (c.624 - c.546BC) that is thought to have made the first major discovery in astronomy, namely that the Earth was not flat as previously thought, but in actual fact a globe. There is, however, no remaining clear evidence of his work and so when Aristotle (c.385 - c.325BC) advanced and publicised this work the first real argument for the Earth being a globe was realised.

Other notable achievements of the Greek astronomers are Eratosthenes' stunning achievement of calculating the Earth's circumference to within a few percent of the modern value and Aristarchus' attempts to calculate the size and distance of the Sun and the Moon, and although his figures were substantially short of the modern day values he did correctly establish that the Sun is much larger and further away. Later, Hipparchus of Nicaea developed trigonometry to calculate the distance of the heavenly bodies relative to the Earth, his results for the moon came out as 29.5 Earth diameters (the modern value is closer to 30!).

Perhaps the most famous and important theory the Greeks proposed was the idea of the geocentric universe.

Ancient Greek Geocentric Universe From Peter Apian, Cosmographia (1524)

Geocentric Universe - Simplified Version From: M.Poole, Beliefs and Values in Science Education

Pythagoras was the first astronomer to suggest this theory, which included the universe having concentric spheres into which the Sun, the Moon and the five 'wanderers' (the known planets - Mercury, Venus, Mars, Jupiter and Saturn were known to exist at this time, the other planets were not found until after the renaissance) were embedded. It was, however, observed that the planetary motions were not following such exact patterns as shown in the diagrams above (i.e. they were not observed in the sky where they should be if they were following perfectly circle orbits around the Earth).
Eudoxus of Cnidus' response was to extended the theory by adding further spheres in an attempt to explain the observed motion.
Aristotle then developed the theory further by again increasing the spheres and further added the idea of a region outside the wanderers, the fixed stars, which he called the heavens and this, he suggested, was controlled by divine methods.
This model, that Aristotle had proposed, became the widely accepted truth in ancient Greece.

It should be noted that the above mentioned Aristarchus was the first to propose a heliocentric theory, only about 100 years after Aristotle's theory, however this theory led to him been ridiculed in his time!
This was mainly down to the popularity of the geocentric theory, but also the idea of the Earth actually moving was widely felt as a foolish suggestion because, as they saw it, if the Earth was moving they would be able to feel it.

So work continued on revising the geocentric theory, attempting to solve the problem that the observed motions of the planets still did not fit in with their theories of the universe.
Then Hipparchus, who as already mentioned calculated the distance of the other bodies relative to the Earth, produced a theory that instead of using spheres to explain the motion of the planets he would use circles, or more accurately epicycles (a compounding of circular motions).

Claudius Ptolemaeus (also known as Plotemy) then extended this work and his greatest undertaking, The Almagest (as it became known) detailed his system of planetary motion. He proposed each planet circled the Earth on an orbit called a deferent and each planet in turn revolved in a smaller circle, around a point moving on the deferent, called an epicycle.
As he attempted to explain all the observed motions of the planets (it was actually retrograde motion that caused the greatest problem) his theory developed to include at least 80 epicycles until, finally, his system could explain and accurately predict the movement of the bodies.
This theory was to become known as the Ptolemaic System.

This system is very significant because it finally allowed the model to fit perfectly with their observations and so quash any doubts of the geocentric universe. After Plotemy's death (in c.180AD) very little work was done in the science of astronomy for nearly 1500 years, so this theory remained unchallenged, and thus the accepted truth, until the 16th century.

The most fascinating part of these early beginnings of astronomy is that all of this work was based upon simple observation with the naked eye (the telescope would not be invented for another 2000 years!). They applied their observations to mathematics and logic and managed to extrapolate theories and estimations that were so accurate that even today we have to stand back and marvel at their achievements.

Note: Of course the geocentric theory was inaccurate, but given the data they had at that time it is a logical and understandable conclusion that the Earth was stationary and it was the other bodies that were moving around it.

The Greeks are not only responsible for the first scientific and mathematical work to be done on the planets and stars but also the first work of science fiction can be traced back to them. The first recorded fantasies of travelling in space appear to have been the work of Lucian of Somosata, around the second century AD. Several of his stories involved man travelling to the moon, and the methods that he wrote of reaching the moon were certainly novel; one of his accounts used a great storm that whisked the ship away, in another the men strapped wings to their arms and they jumped off a great mountain top and flew to the moon! Of course he did not believe that these were realistic ideas, but fiction at this time was more concerned with trying to teach morality.

It was mentioned above that very little work was done on astronomy for nearly 1500 years after the Greeks, indeed there was very little work in any field that contributed any advances towards man's attempts to reach the stars until the first use of rockets, sometime around the 11th century. These rockets were used by the Chinese and were solid fuel rockets, using gunpowder as their propellant. Gunpowder is thought to have been developed in China somewhere around the 8th century AD (a very long time before Guy Fawks!), and it is clearly recorded that in 1044 the exact formula for gunpowder was written down. It appears that rockets were part of Chinese military tactics as early as 1050 as there is frequent mention to them within the Chinese military writings of that time and certainly by 1232 they were being used by the Chinese in their war against the Mongols.

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