Einstein gave us two relativity theories, and boy are they different beasts! Special relativity is the friendly golden retriever – straightforward equations about light speed and time dilation that undergrads can handle. Then there's General Relativity – a terrifying monster with tensor calculus, differential geometry, and spacetime curvature that makes even PhD students wake up screaming. The math goes from "E=mc²" to "Rμν - ½Rgμν = 8πG/c⁴Tμν" real quick. Ever tried solving the Einstein field equations? That's not homework, that's psychological warfare.