How did astronomy become connected with physics?

The connection between astronomy and physics has evolved significantly, transforming from the study of celestial motions to a deep integration of physical laws across the universe.

The foundation for this link was established during the Scientific Revolution. Celestial mechanics served as the first testing ground for Newton’s laws of motion, which successfully unified terrestrial and celestial physics under a single set of principles. By applying the concept of gravitational force, Sir Isaac Newton provided a physical basis for Kepler’s laws of planetary motion, demonstrating that the same forces governing objects on Earth also dictate the orbits of the Moon and planets.12

In the 19th century, the emergence of astrophysics further bridged these fields by focusing on the physical and chemical properties of celestial bodies. This connection deepened in the 20th century through spectroscopy, which allowed scientists to determine the composition of stars, and through cosmological theories rooted in the theory of relativity. Today, theoretical astrophysics relies on validated physical laws to model complex cosmic phenomena, ensuring that our understanding of the universe remains consistent with the fundamental principles of physics.13