This lab activity focuses on modeling the expanding universe by calculating the recessional velocities of galaxies at various stages of expansion. Students will use a balloon to simulate the universe's expansion, identifying different 'galaxies' on the surface of the balloon. Measurements will be taken at three stages of inflation to determine how the distance between galaxies changes over time. Students will calculate the velocities of each galaxy based on the change in distance and time, analyze the data to determine Hubble's constant, and plot their findings on a velocity-distance scatter plot. This exercise aims to illustrate the cosmological principle by demonstrating that more distant galaxies recede faster, thereby deepening students' understanding of the dynamics of the universe.