Explore the fascinating realm of cosmology in this comprehensive lecture on the universe and multiverse theories. Delve into key concepts like the expanding universe, cosmic microwave background, and the age of the universe. Examine troubling aspects such as the horizon and flatness problems, and discover how inflationary theory attempts to resolve these issues. Learn about cosmological phase transitions, symmetry breaking, and gauge theories of elementary particles. Investigate various inflationary models, including chaotic and eternal inflation, and their implications for the multiverse concept. Contemplate profound questions about the beginning of the universe and alternative cosmological models like cyclic universes. Gain a deeper understanding of cutting-edge ideas in theoretical physics and cosmology through this engaging 2-hour lecture by G. Srinivasan from the Raman Research Institute.