Over the years the models of the solar system have developed massively and have followed trends of the time such as religion and/or science. As science has taken a step forward so have the ideas of the solar system.
The earliest ideas regarding solar systems were developed by the Chinese (c3000 -2000BC). For the time they lived in their ideas were very advanced and accurate in some areas such as length of a year. They calculated the year to be 365.25 days by dividing a circle into 365 degrees [1]. They measure time by dividing the sky into 12 branches and 10 stems, arranged around the ecliptic to give a 60 year cycle. They were very observant and as there are records of them observing: comets, sun-spots, novas, and solar flares.
Following the Chinese was a civilisation called the Chaldeans (from 1200BC) they lived in the area which is now known as Iraq and Kuwait. They created the ideas of 60’s for time (60 seconds in a minute, 60 minutes in an hour). They reached a conclusion that the earth, moon, 5 planets and our sun are all part of one system [2]. They also measured the solar year to such accuracy that modern computers faulted it to only 4mins 30seconds. They also invented the zodiac system.
The first people to develop physical models of the solar system were the Egyptians and Greeks as there timing overlapped. These ideas were similar in some ways as they all put the sun at the centre of the system.
The first recorded model is Thales showing sun, moon, and star solids, showed the moon was lit by the sun, he also managed to measure the diameter of the sun. However, even though his ideas were advanced he thought the earth was flat [3].
Alaximander’s model (4) came soon after Thales, his model showed the earth at the centre surrounded by air and clouds then the horizon, and then a region of fire. Leucipus(5) developed the next model which slightly more advanced as it took into the stars which are further away than the sun, the problems of his model were that earth was still at the centre surrounded by the moon then the planets, which were all at the same distance away from the earth, which he still believed to be flat.
Pythagoras’s model (6) was more detailed as it put the planets in order away from the earth. After air and clouds. The problems with his model are that he puts in the celestial fire which is not present, he also puts in a ring for Olympus, and this shows how religion affected models as he put in an area for the goods. The reasoning behind him believing the world was round was by observing the moon and other bodies, which were round so believed that so would the earth.
Philolaus of Croton moved a major step forward by introducing a central fire, this is important as it meant that the earth was not in the middle of the solar system. The central fire was believed to be god, so there was a counter earth put in as it was believed man could not look upon god. The next model was by Aristotle (7), who moved back to the old model with the sun in the centre surrounded by the sun and the planets. He put the in order that he believed was correct making the model much more detailed. He did end up accept that the earth was round on empirical grounds.
The models that followed this era changed dramatically as the earth was no longer in the centre but the sun was. This was hard for religious people to understand as they thought that everything should revolve around the earth.
Copernacus (8) wrote a book called De Revolutionibus Orbium Coelestium in which he presented his new ideas of the solar system. He had a sun centered universe and that the planets orbited it. To explain the movement of some of the planets he used epicycles, which is where the planet circles its obituary path. The ideas that were developed were presented as a working hypothesis so were not widely taken in. This model is a huge step forward as it put the sun in the centre and the planets around it.
Tycho Brahe developed a new model that was taken in more than Copernacus’s model as it returned to having the earth at the centre. It did improve as he did not use epicycles. Kepler, who worked for Tycho, developed 3 laws which improved the idea of the solar system, the most important of which was that the planets orbits were elliptical not circular which explained the pattern of motion of the planets.
Models of the solar system are much more advanced in modern times due to huge advances in technology, equipment and knowledge. Due to the introduction of powerful telescopes and robotic explorations our knowledge of the solar system has greatly improved. The plants are now divided into two groups [9], the terrestrials - Mercury, Venus, Earth and Mars and the gas giants - Jupiter, Saturn, Uranus and Neptune.
Uranus, Neptune and Pluto had not been discovered by the former historic mechanical models used to describe the solar system above. The discovery of Neptune was controversial as Neptune was theorized to exist due to irregularities noted in orbit of Uranus which implied something, it was not proven to exist until several years later.
Pluto even though it was discovered as a planet in recent times (1930), it has since been reclassified as a dwarf planet as part of the Kuiper Belt of asteroids/dwarf planets, which lies just outside Neptune’s orbit.
Our knowledge of our solar system has greatly improved in modern years due to massive advancements in technology and the decreased influence of the church. Even though it is clear we now have a much greater knowledge of the solar system it cannot be taken away from historic societies’ i.e. The Ancient Chinese, The Chaldeans or The Greeks who made huge discoveries in astronomy without the use of our modern day technology.
Bibliography:
5. http://www.mlahanas.de/Greeks/Bios/Leucippus.htm
7. Powerpoint
8. http://www.conservapedia.com/Nicolaus_Copernicus
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