Explore the potential endings of our universe in this 54-minute lecture by theoretical astrophysicist Katie Mack. Delve into major concepts in quantum mechanics, cosmology, and string theory, discovering how small adjustments to our current understanding of reality can lead to vastly different cosmic conclusions. Journey through topics such as the Hubble Ultra Deep Field, expanding universe, galaxy distribution, microwave radiation, black body spectrum, galaxy collisions, dark energy, the Big Rip, cosmological constant, heat death, Higgs field, quantum tunneling, and vacuum decay. Gain insights into the complex workings of our universe and contemplate its ultimate fate in this thought-provoking presentation from The Royal Institution.