General relativity was developed after special relativity for several reasons. Here are some key factors:
Special relativity as a foundation: Special relativity, developed by Albert Einstein in 1905, provided a groundbreaking framework for understanding the behavior of objects moving at constant velocities in the absence of gravity. It introduced concepts such as the constancy of the speed of light and the equivalence of mass and energy (E=mc²). Special relativity was a significant leap forward in our understanding of space, time, and motion, but it did not account for gravity.
Need to incorporate gravity: Gravity was a missing piece in the puzzle of understanding the fundamental forces of nature. Einstein realized that special relativity could not account for the force of gravity, which acts as a curvature of spacetime caused by massive objects. He embarked on a quest to develop a theory that could encompass both gravity and the principles of special relativity.
Equivalence Principle: The Equivalence Principle, proposed by Einstein in 1907, was a key guiding principle in the development of general relativity. It states that the effects of gravity are indistinguishable from the effects of acceleration. This principle suggested that gravity is not simply a force acting on objects but rather a manifestation of the curvature of spacetime.
Geometrization of gravity: Einstein realized that in order to incorporate gravity into a relativistic framework, he needed to describe it in terms of geometry. He proposed that the presence of matter and energy curves the fabric of spacetime itself, causing objects to follow curved paths. This idea formed the basis of the mathematical framework of general relativity, where the geometry of spacetime is determined by the distribution of matter and energy within it.
Development of the field equations: Einstein spent years working on the mathematical equations that would describe the curvature of spacetime in the presence of matter and energy. These efforts culminated in the development of the field equations of general relativity in 1915. These equations relate the distribution of matter and energy to the curvature of spacetime, providing a precise description of how gravity operates.
Experimental confirmation: General relativity made several predictions that were distinct from classical physics and special relativity. These predictions included the bending of light around massive objects, the precession of the perihelion of Mercury's orbit, and the gravitational redshift of light. Over time, these predictions were experimentally confirmed, providing strong evidence for the validity of general relativity.
In summary, general relativity was developed after special relativity because special relativity laid the foundation for understanding motion in the absence of gravity, while general relativity aimed to incorporate gravity into a comprehensive relativistic framework.