Inertia
Albert Einstein's theory of special relativity, as proposed in his 1905 paper entitled "On the Electrodynamics of Moving Bodies" was built on the understanding of inertia and inertial reference frames developed by Galileo and Newton. While this revolutionary theory did significantly change the meaning of many Newtonian concepts such as mass, energy, and distance, Einstein's concept of inertia remained unchanged from Newton's original meaning (in fact, the entire theory was based on Newton's definition of inertia). However, this resulted in a limitation inherent in special relativity: the principle of relativity could only apply to reference frames that were "inertial" in nature (meaning when no acceleration was present). In an attempt to address this limitation, Einstein proceeded to develop his general theory of relativity ("The Foundation of the General Theory of Relativity," 1916), which ultimately provided a unified theory for both "inertial" and "noninertial" (accelerated) reference frames. However, in order to accomplish this, in general relativity, Einstein found it necessary to redefine several fundamental concepts (such as gravity) in terms of a new concept of "curvature" of space-time, instead of the more traditional system of forces understood by Newton.
Criticism of the theory of relativity
It was also claimed that special relativity cannot handle acceleration, which would lead to contradictions in some situations. However, this assessment is not correct, since acceleration actually can be described in the framework of special relativity (see Acceleration (special relativity), Proper reference frame (flat spacetime), Hyperbolic motion, Rindler coordinates, Born coordinates). Paradoxes relying on insufficient understanding of these facts were discovered in the early years of relativity. For example, Max Born (1909) tried to combine the concept of rigid bodies with special relativity. That this model was insufficient was shown by Paul Ehrenfest (1909), who demonstrated that a rotating rigid body would, according to Born's definition, undergo a contraction of the circumference without contraction of the radius, which is impossible (Ehrenfest paradox). Max von Laue (1911) showed that rigid bodies cannot exist in special relativity, since the propagation of signals cannot exceed the speed of light, so an accelerating and rotating body will undergo deformations.