Four seasons, four elements, four directions... four humours. In ancient Greece it seemed clear that just as our world was built from four elements, our bodies must be regulated by four vital fluids. When these humours fell out of balance, disease and bad moods followed. For centuries doctors practiced medicine based on this idea: identify which fluid is winning and remove some of it until the patient stops complaining. It wasn’t until the 20th century that a discovery truly revolutionised medicine and finally laid this theory to rest. Cure your curiosity and listen to this week’s episode of Good in Theory.

How do animals adjust to changing environments? Why are some living things much more complex than others? Before Darwin came up with his theory of evolution, Jean-Baptiste Lamarck had a theory of evolution of his own. Instead of using language such as “mutation” and “natural selection”, his theory is one of gradual and intentional change. “Extinction” was also not in his vocabulary, instead he talked about “spontaneous generation” and “complexifying force”. To evolve your understanding of Lamarck's theory of evolution and how it was used culturally and politically, listen to this week’s episode of Good in Theory.

Clear skies, fresh air, that must mean there are no diseases here? For millennia people believed that the spread of diseases was connected to the quality of the air. If the air was cold, polluted and smelt rotten you were sure to get infected with cholera or the black plague if you were out too long. Miasma theory had an enormous impact on people's habits and even the economy of southern China. It was only in the 19th century that this medical belief was seriously challenged, which led to more effective ways of dealing with pandemics and the prevention of many deaths. For tips on hygiene and disease control listen to this week’s episode of Good in Theory.

Water waves are movements in water, so light waves are movements in… aether. At least that was the leading theory in the 18th century. Sounds simple enough but nailing down what this aether is leads to curious properties. In truth light waves are quite different from water waves in many respects including that their speed is constant no matter how fast you yourself are going. The history of aether theory is tied to the emergence of both quantum theory and relativity. It records how scientists struggled to let go of their intuition and see the reality of space and time in a new light. Join us on our mission to understand the true nature of light and listen to this week’s episode of Good in Theory.