Special Relativity is concerned with the laws of physics in inertial frames of reference, while General Relativity deals with the effects of gravity and acceleration on the laws of physics. Special Relativity is a special case of General Relativity, which takes into account the effects of gravity on the laws of physics.
Einstein developed the theory of Special Relativity in 1905 and General Relativity in 1915 through thought experiments and mathematical equations. He was inspired by the work of other scientists, such as Maxwell's equations on electromagnetism, and his own curiosity about the nature of space and time.
The key principles of Special Relativity are the constancy of the speed of light, the relativity of simultaneity, and the equivalence of mass and energy. The key principles of General Relativity are the principle of equivalence, the curvature of spacetime, and the geodesic principle.
Several experiments and observations have confirmed the predictions of General and Special Relativity, such as the bending of light by massive objects, the slowing down of time in strong gravitational fields, and the gravitational redshift of light. The most famous and precise confirmation is the observation of the perihelion shift of Mercury, which was predicted by General Relativity.
General and Special Relativity have many practical applications in modern technology, such as GPS systems, which use the principles of General Relativity to correct for the time dilation of satellites in orbit. Special Relativity also plays a crucial role in particle accelerators and nuclear reactors. The theories have also had a significant impact on our understanding of the universe and have helped us make advancements in cosmology and astrophysics.