The author, a mathematics teacher, describes a seventh grade class where students use scientific notation to calculate how long it takes light to travel a variety of astronomical distances and then interpret the significance of their findings. Ultimately, the goal is to have students see how calculations can help answer large, almost philosophical questions about the universe. At the end of the study, students are asked to weigh in on the question of how full or empty the universe is, understood in a much more sophisticated light against the backdrop of their travel-time calculations. This STEM activity integrates mathematics and science inquiry in a creative, insightful way that naturally and simultaneously incorporates many of the practice standards for mathematics, science, and engineering.