Explore the fascinating world of quantum field theory in curved spacetime through this 58-minute lecture by Níckolas de Aguiar Alves from the Galileo Galilei Institute. Delve into the intriguing question "Why Do Things Fall?" as the speaker guides you through key concepts including quantum field theory, coordinates, and equations. Gain insights into notable phenomena such as the Hawking Effect, the Unruh Effect, and the Unruh Vacuum. Examine practical examples and discover the implications of the Boulware Vacuum. This thought-provoking talk offers a comprehensive introduction to the complex interplay between quantum mechanics and gravity, providing a solid foundation for understanding the behavior of particles and fields in curved spacetime.