Why did the Lincoln Memorial Reflecting Pool turn green?

Why is Europe experiencing a heatwave? What happens if a being from a different dimension enters our dimension? Why are wombats able to produce square-shaped faeces? Can we live without sodium? Is there a scientific explanation for xenophobia? Why did the Lincoln Memorial Reflecting Pool turn into a green swamp? What causes early morning phlegm, even without a cold? Dr Chris Smith and Clarence Ford have the answers... Like this podcast? Please help us by supporting the Naked Scientists (thenakedscientists.com/donate)