A cosmologist is a scientist who studies the universe's origins, structure, and evolution. They explore big questions about how the universe began, what it's made of, and how it changes over time. Using tools like telescopes and computer simulations, cosmologists analyze data from distant galaxies and cosmic events to understand the laws of physics that govern everything around us. Cosmologists often work with concepts like the Big Bang, which is the leading theory about how the universe started, and dark matter, a mysterious substance that makes up most of the universe's mass. Their research helps us grasp our place in the cosmos and the fundamental nature of reality.