Home, sweet home.

There is only one place to begin when discussing the Universe, and that's right here at home. Our planet is home to a vast wealth of culture, diversity, colour and vibrance, yet though we may understand much about our own world today, in the past it has also been a place of mystery and enigma.

The tale of Astronomy begins in ancient times, possibly with the Babylonians. However, many cultures have formulated their own hypotheses and folk-lores around the heavens, seeing the stars and planets wheeling unassailably above as gods, demons and portents. The movements of the heavens were both employed as mystical tools to foretell great victories or terrible happenings, or used agriculturally and navigationally to stand as a sign of when to plant crops or what direction in which to sail. At times like these there was little to tell, if anything, between Astronomy and Astrology, though they could not be further apart today.

The ancient Greeks in particular began to treat Astronomy as a particular and specific science. Indeed it is from the Greek planetes, meaning 'wanderer' that we derive the term 'planet' today. The reason for this naming is that the ancient Greeks among others noticed something remarkable about the night sky, and it was this which began to open the doors to a greater understanding of the Universe around us. Firstly, they noticed that the stars at night held fixed positions, although as a group they seemed to rotate around us. Year after year they would remain in the same places relative to each other as they spun around amid the inky blackness of the heavens.

This observation led to two suppositions:

1: that the Earth rotated about its axis, and
2: that the Earth was at the centre of the Universe (whatever that might be!).

The next observation was one that, unbeknownst at the time, would eventually help to unseat that second premise. The Greeks noticed that aside from the fixed stars that wheeled above ever and anon, there were five wandering stars, the planets, whose positions did not remain fixed as the years went on. They seemed to follow their own paths, sometimes racing across the sky in one direction, and then another time drifting back from whence they came.

This apparent aimlessness of the planets perplexed the ancients for centuries. That the Sun, Moon and stars rotated around the Earth (or at least appeared to do so) was plain to see. How could these other stars be any different?

Eventually, Aristotle began work on the idea that these wanderers were fixed to seven crystal spheres, along with the Sun and Moon, called 'epicycles', which sat one inside another with the Earth at the centre. In this fashion he tried (not particularly accurately, but better than any at the time) to predict the positions of the planets from one year to another. 

Whilst this view may seem laughable to us in the modern era, it is easy to see how such mistakes could have been made without the use of telescopes, satellites and all the technology that we are so enamoured of today. Indeed, the ideas of Aristotle lasted until the 16th Century.

At this time came Mikołaj Kopernik, otherwise known to us as Copernicus. He for the first time introduced the idea that the Earth was not at the centre of the Universe, but that the Sun held that particular honour. Indeed, whilst this view was still incorrect, it was the first time that someone had begun to realise the truth about mankind's place in the cosmos.

It was then left until the coming of Galileo Galilei that the geo-centric model of the Universe could finally be shattered, although it was not permitted at the time and Galileo was punished for his work. He showed, by looking through a new invention (the 'telescope') that the planet Jupiter had four moons rotating about it. These moons are known to this day as the 'Galilean' moons in his honour, as he showed for the first time that it was possible for a something to orbit a body other than the Earth. Well, though the Catholic Church tried their best to refute the idea, geo-centrism was done for. Johanness Kepler was next on the scene, showing that the planets move in predictable ways around the sun, in an effort that finally ousted the work of Aristotle from around 1,300 years before. For the first time, one could make a calculation that would precisely pinpoint the position of a planet many years in the future with perfect accuracy. In fact, Kepler made three postulates, which are now known as Kepler's Laws:

1. A planet travels around an elliptical orbit, with the sun at one of two foci,
2. An imaginary line drawn between a planet and the sun sweeps out equal areas in equal times, and 
3. The orbital time (year) of a planet depends on it's distance from the sun (or the square of the orbital period of a planet is proportional to the cube of its semi-major axis in full).

With these three ideas, Kepler paved the way for Modern Astronomy to begin in earnest. His last law is used by astronomers today, particularly by the space-borne observatory that bears his name, the Kepler Space Observatory. This marvellous device hunts for distant planets among the stars by observing the tiny dip in light as a planet moves in front of its parent star. Using Kepler's third law, scientists can determine the distance of a planet from the star, and even its mass.

Since Kepler, Astronomy has been less a study of the mystic and supernatural, and more a study of real, testable phenomena. Since his time we have learned much about stars, planets, galaxies and all manner of astrophysical objects, yet none of it would have been possible without these early pioneers and thinkers, who often risked their reputations, even their lives, to think past conventional wisdom and seek the ultimate truths of our existence.