Albert Einstein had difficulties relating his theory of general relativity to quantum physics primarily due to fundamental conceptual and mathematical differences between the two theories. Here are a few key reasons for Einstein's struggle:
Incompatibility of frameworks: General relativity and quantum mechanics are built upon different theoretical frameworks. General relativity describes the behavior of gravity and the curvature of spacetime on a macroscopic scale, while quantum mechanics deals with the behavior of particles and fields on a microscopic scale. The two theories have different mathematical formalisms and describe different phenomena, making their integration challenging.
Uncertainty principle and determinism: Quantum mechanics introduces the principle of uncertainty, which states that certain pairs of physical properties (e.g., position and momentum) cannot be precisely determined simultaneously. This conflicts with Einstein's belief in determinism, the idea that the precise state of a system can be determined at any given time. Einstein famously stated, "God does not play dice with the universe," expressing his skepticism towards the probabilistic nature of quantum mechanics.
Non-locality and entanglement: Quantum mechanics exhibits non-local behavior, where the measurement of one particle can instantaneously affect the state of another particle, even if they are separated by large distances. This phenomenon, known as entanglement, was deeply unsettling for Einstein, who preferred a local and causal explanation for physical phenomena. He referred to this as "spooky action at a distance" and sought a more local and deterministic interpretation.
Lack of a unified theory: Einstein spent much of his later years attempting to develop a unified theory that could reconcile general relativity and quantum mechanics. He sought a single framework that could explain the behavior of both gravity and quantum phenomena. However, he was unable to find a satisfactory solution, known as the "Theory of Everything" or a "quantum theory of gravity," which would unite the two theories into a comprehensive framework.
It's worth noting that subsequent generations of physicists have made progress in bridging the gap between general relativity and quantum mechanics, particularly in the field of quantum gravity and string theory. However, a complete and universally accepted theory that seamlessly combines both remains an open challenge in modern physics.