Extending angles into the vastness of space

Students often struggle to grasp the vast distances that the study of astronomy demands. Obviously, we cannot travel these distances, so direct experience is limited. We must peer out at the universe through our eyes (or substitute technology). This adds a further complication, because we do not see linear sizes—we perceive angular sizes—but our brains get so good at translating these perceptions into linear interpretations that students often struggle to recognize and interpret the meaning of angular sizes. I present here a sequence of simple activities that can get students more comfortable in working with angular size measurements, starting with simply holding up their pinky finger at arm’s length. Step by step, the students can extend the angular size of their finger out into their environment, to measure nearby objects, the Moon, the Sun, and even distant galaxies.