This learning activity, titled "The Cosmic Chronometer: Closure Activity," guides students through applying their understanding of Hubble's Constant to predict the recessional velocity of a hypothetical galaxy. Students begin by revisiting their lab data to determine the slope of their line of best fit, which represents their specific Hubble's Constant. They then use this constant to calculate the velocity of Galaxy 'Z,' which is positioned a specified distance away in their balloon model. Finally, the activity encourages students to reflect on the relationship between distance and velocity in an expanding universe, prompting them to reason why galaxies further from the origin move away at higher velocities. This fosters a deeper understanding of cosmic expansion and the dynamics of galaxies.