Ensidia

Thousands of years ago when our ancestors gazed up at the night sky, they noticed something other than how impressive everything looked. They noticed that like the sun during the day, the stars also moved across the sky from east to west throughout the course of the night. It was also noted that the stars held their position in relation to one another, or at least, most of them did.

The more observant and diligent studiers of the night sky soon became aware that there were a few points of light that seemed to have other ideas. These unruly specks of colour tended to move at a different rate and sometimes in different directions to their sparkly companions, performing a looping motion every now and then over the course of a few months. In Greece these wayward astral bodies were given the name of "wanderers" which in ancient Greek was "planetes" and has become to us, "planets".

Faced with the behaviour of these planets, people assumed that they were alive and possibly gods, and in fact it would probably be a good idea to kill a goat or something because they might like that. Many years and countless goats later, the common scientific consensus was that although these planets may not actually be gods after all, they were still exerting effects on peoples lives, and astrology was born. As far as we know no one has apologised to the goats yet. 

At first there was no perceived difference between the study of astronomy and astrology, both were seen as being all the same subject. Thankfully these days we understand astronomy as the study of a wonderful, fascinating material universe, and astrology as a load of absurd rubbish promoted by the kind of irritatingly vague, floppy-haired people you try to avoid getting stuck talking to at parties. The journey to this happy state of affairs was made possible by the hard work of many genius' and I would like to remember a few of them here.

2000 years ago, Claudius Ptolemy was plying his trade as the foremost astronomer/astrologer of his time. Ptolemy had an idea about why the planets appeared to move around the sky in the way they did. His theory was that the Earth was the centre of the universe and the sun and all the planets revolved around us. On the 'Scientist-O-Meter' Ptolemy scores highly for ego but poorly for getting things right. However the ego card is always a strong one to play and his theory was embraced by pretty much everyone for the next 1500 years.

The "looping" movement of the planets as observed from earth caused a few problems for Ptolemy's theory, which he addressed by asserting that the planets move in smaller circles of their own whilst orbiting the earth, as pictured:

This theory remained unchallenged until 1543, when Nicolaus Copernicus published his book "On the Revolutions of the Celestial Spheres" and then died as fast as he was able. Some stories say the first copy of the published book was placed in his hands on his death bed. (This story is difficult to prove, and I sometimes wonder if it was an invention of his publishers, who could then advertise the book with the strap line that: "People are just dying to read it.")

Copernicus' book challenged Ptolemy's order by setting the sun at the centre of the solar system, with the earth and planets orbiting around it. This theory removed the need for the planets to be performing fiddly little circles of their own, and had the added bonus of being largely correct.

Sadly, some people are extremely resistant to truth. Some years later Copernicus' work began to be suppressed by the Catholic Church and his book was eventually banned. Galileo was to find out just how strongly the Church felt about this issue when after a running debate over the matter, he was finally ordered confined to his house, where the great man was imprisoned until his death.

Galileo's suffering apart, all the Church really managed to accomplish through this behaviour was to shift the cutting edge of scientific thought from the Mediterranean area into the Protestant north of Europe, as free thinkers voted with their feet for a more conducive environment to learning.

Another key player in the process of rescuing astronomy from it's association with astrology, was born 28 years after Copernicus' death, on the 27th of December 1571, he was called Johannes Kepler. Kepler was an unlucky man, as is clearly demonstrated his date of birth. As many people will know to their cost today, being born that close to Christmas is a sure way to miss out on untold gifts and numerous parties, as relatives combine celebrations for both events for the purposes of convenience.

Overcoming this obstacle, Kepler grew into a highly intelligent man who found a great passion for Geometry. To him, the kind of perfection available only in mathematical shapes was a glimpse of the divine, in his eyes Geometry was the beauty of God's handiwork revealed. Being so infatuated, he developed a theory that the planets, their orbits and their places in the solar system were the product of some sort of cosmic order based around these perfect geometric shapes. He spent much of his life trying to match the data available to him with his grand theory of geometric order. To his great dismay he was never able to do this, because it turns out that he was completely and utterly wrong.

From this you might get the idea that Kepler was a failure, but I'm glad to say this isn't the case. During the pursuit of his elusive theory, he was forced to admit that the idea of circular orbits didn't tally with the most accurate data he could find, and in admitting that he was wrong, promptly discovered that planetary orbits were elliptical. This led to him going on to write his laws of planetary motion, which played a huge part in the foundation of modern astronomy.

What I personally admire about Kepler was the way in which he thought of the planets. To him they were not vague magical objects that interfered with peoples' lives, they were real places, just like the Earth. We can see this in his writing of one the first ever science fiction books, called "The Dream", in which humans voyage to the moon and are described viewing Earth from that vantage point. He believed that one day mankind would journey from our world and travel about the solar system in celestial crafts. To say he was ahead of his time in these respects would be a  major understatement.

I also think Kepler deserves special praise for the way in which he never let his personal desire to prove his great theory become more important than the evidence. It is this integrity that I see as the mark of a true scientist, and one that deserves our admiration. So I hope that next time you are laughing in disbelief at some imbecile who believes the arrival of Jupiter in a certain part of the sky as seen from earth, will have profound implications for their love life, that you might spare a thought for the people who played their part in dragging us away of that particular superstition and into the light.