Lecture 7 - The Realm of the Galaxies
The `Great Debate' or the `Shapley–Curtis Debate' between the astronomers Harlow Shapley and Heber D. Curtis set the tone of our investigations into the nature of galaxies in the early twentieth century. This lecture delves into the questions addressed at that debate and many others in the light of the progress made since then.
A hotly debated question at the dawn of the twentieth century concerned the size of our universe, and whether there are other galaxies besides our Milky Way Galaxy. Another important question concerned the different stellar populations in our Galaxy, and the spatial distribution of stars. This lecture explains the various momentous discoveries that answered these questions.