These lecture notes from Michael Fowler, Physics professor at University of Virginia, explore "two revolutions in our perception of the universe," the impacts of Galileo and then Einstein on our understanding of physics. The 27 lectures included here may be a useful supplement and teaching aid for educators. The lectures begin with the early Greeks and follow the progress of scientific thought through the work of Galileo, Isaac Newton, and Einstein. The lectures themselves are clear and offer interesting historic details and a conversational approach to explaining concepts. Though the lectures were written a few years ago, the content is timeless, and many of the lectures have been recently updated.