In this NASA article I learned how astronomoers use Cepheid variable stars and Type Ia supernovae to measure distances between galaxies and prove that the universe is expanding. \Hubble first discovered this expansion.newer observations from Hubble and Webb have shown that the expansion is actually speeding up due to dark energy. I found it interesting how measuring light from distant galaxies can reveal both the universe’s growth and its very own history. This article helped me better understand how astronomers combine observations and technology to study the size, expansion, and age of the cosmos.