Noticing the regularities and the changing behaviour of the heavens was pretty much a commonplace amongst early peoples, and probably every early society had some sort of model or explanation – somewhere between the theological and physical – about the motions of the heavens. Once the ancient Greeks had begun to think about nature as part of ‘philosophy’ and distinguished between explanations that involve the divine and explanations that do not invoke the supernatural, the material nature and the natural causes of the observed heavens became a completely different kind of ‘philosophical’ [that is, scientific] question.
The development of theories about the nature and behaviour of the heavens based on reason was not exactly easy: there is no possibility of any sort of empirical knowledge other than seeing pinpricks of light moving very slowly against the background of fixed pinpricks of light. So everything that follows is going to be speculation, but speculation based on some sorts of reasoning and criteria of what we think the world – or the heavens – must necessarily look like. For all that the ancients thought that the heavens are different from the world around us, inevitably ancient (like modern) natural philosophers will use their thinking about the local world to help understand or guess what might be happening in the heavens. What is really interesting about ancient cosmology and astronomy is how they tried to construct theories about the large scale structure of the universe. If it is not all just the incomprehensible domain of the supernatural, how do we work out what is going on up there?
It is hard for those of us in the 21st century to grasp how little the ancients knew about the heavens, and how hard it was for them to come up with any models for what was going on beyond the surface of the earth. Everyone knew the earth was a sphere (no: no flat-earthers in the ancient world), but beyond that it was pretty unclear. In these lectures, we will trace a few of the major ideas the ancient Greeks had about the large scale structure of the world, how they argued about these ideas, and how they developed over the thousand-year history of ancient Greek scientific thinking (very roughly 500 BC to 500 AD). If there is time, we will look at the most amazing thing to come from the ancient world and ancient astronomy, technologically infinitely more interesting – and amazing – than the pyramids or Stonehenge or anything else.
The lectures will not involve any hard technicalities, but a sense of humour and a sense of wonder are essential.
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