In our first lecture, Dr. Keating embarks on a captivating journey through the cosmos, exploring the universe's vastness and introducing us to the tools used to unravel its mysteries. We delve into the history of cosmology, from ancient cosmological models to the groundbreaking discoveries of Galileo, Newton, and Einstein, and discuss the challenges and limitations of conducting experiments in astronomy and cosmology. The lecture highlights the incredible advancements in telescope technology, from Galileo's modest instrument to the James Webb Space Telescope, and the exciting possibilities they offer for understanding the universe's origins, structure, and future.

In lecture two, we explore the pioneering contributions of early astronomers like Kepler and Galileo, who laid the foundation for modern astronomy despite their limited tools. We then delve into the methodology of the cosmic distance ladder, a series of techniques used to measure distances in the universe, from our nearest neighbors to the most distant observable objects. Dr. Keating introduces key concepts such as parallax, standard candles like Cepheid variable stars, and the luminosity distance method. Finally, we tackle Olbers' paradox, which questions why the night sky is dark if the universe is infinite and eternal, suggesting the possibility of a finite and expanding universe.

In lecture three, we examine compelling evidence that the universe is expanding, highlighted by the work of Vesto Slipher and Edwin Hubble, who observed that nearly all galaxies show a redshift in their spectra, indicating they are moving away from us. We also discuss Hubble's law, which links a galaxy's distance to its redshift, serving as a crucial tool for measuring cosmic distances and providing evidence for the uniform expansion of the universe. The lecture concludes by exploring the profound implications of this expansion, including the possibility of a cosmic origin and the ongoing debate over the precise value of the Hubble constant, which influences the universe's expansion rate and age.