Felix Klein

Felix Klein was a German mathematician known for his work in geometry and topology. Though not a direct contributor to General Relativity, his ideas on spaces and transformations influenced the mathematical framework supporting Einstein's theories. Klein introduced concepts like the Klein bottle and the idea of "non-Euclidean geometry," which expand our understanding of space beyond traditional shapes. His work helped pave the way for the sophisticated mathematical tools that describe the curvature of spacetime, which is fundamental to General Relativity, illustrating how mass and energy influence the structure of the universe.