Wherein we further discuss the nature of distances and sizes in astronomy, and its measurement just positions in the sky. Wherein we chat about how we know the relative sizes and distances of the Sun and Moon to the Earth. Supplement the videos with "OpenStax Astronomy" 1: Science and the Universe 2: Observing the Sky: The Birth of Astronomy 4: Earth, Moon, and Sky Aristarchus of Samos His methods... Angular measures Astronomical Unit The song? This is part of Module 1 of 14 which details an entire online introductory college course. This video series was used at William Paterson University and CUNY Hunter in online classes as well as to supplement course material. In the first lecture, I talk about how we navigate our way around the sky. I talk about the constellations and coordinate systems of the sky. In the second lecture, I decide to practice more so you can learn about the Celestial Sphere, equatorial coordinates, and where stars rise and set. Next, I discuss the motions of the Earth, and reason for the seasons. This leads us to discuss the nature of distance in astronomy, and its measurement with parallax. Once you know distances, we can chat about how we know the size of the Earth, and how that can be used to determine the distance to the Sun, given that Venus does a transit across the Sun. There's more to do, so I continues my discussion of the nature of distances and sizes in astronomy, and its measurement just positions in the sky. Wherein we chat about how we know the relative sizes and distances of the Sun and Moon to the Earth. Finally, I go back in time to discuss the Aristotle's arguments for a stationary Earth, and the construction of Ptolemy's Geocentric Model that ruled the roost for almost 2000 years, until it was dethroned in 1610.