Galileo made significant contributions to the development of physics, including his discovery of inertia through the inclined plane experiment with a small ball. However, the limited understanding of the natural universe in Galileo's era prevented a complete interpretation of his findings. Even today, physicists grapple with fundamental questions such as why matter possesses inertia and what its true nature is. Addressing these questions is critical for refining classical mechanics and interpreting the concept of inertial reference frames. Since Galileo's time, physics has undergone centuries of development, accumulating a wealth of knowledge that was unavailable to early pioneers like Galileo, Descartes, and Newton. This progress has introduced new ideas and methods for tackling fundamental problems in physics. Consequently, it is both timely and necessary to reinterpret foundational classical physics experiments using contemporary insights. This article presents a reinterpretation of Galileo's inclined plane and pendulum experiments, leveraging modern physics knowledge and alternative perspectives. The study reveals that inertia fundamentally arises from the conservation of energy and offers a clear explanation for phenomena such as why an accelerating free-falling elevator qualifies as an inertial frame of reference. It also explores the origins of energy in the universe and reports several other significant findings. These discoveries, which have implications for bridging classical and modern physics, are discussed in detail.