Classical physics and quantum physics are two distinct branches of physics that describe the behavior of the physical world at different scales. While classical physics successfully explains the macroscopic world, quantum physics is needed to understand phenomena at the microscopic level. There are several key differences and issues between classical physics and quantum physics:
Determinism vs. Probabilistic Nature: Classical physics is based on the concept of determinism, where the future state of a system can be precisely predicted given its initial conditions and the laws of physics. In contrast, quantum physics introduces inherent randomness and uncertainty into the behavior of particles. The outcomes of measurements in quantum systems are described by probability distributions, and it is not possible to predict the precise value of an observable with certainty.
Wave-Particle Duality: Quantum physics introduces the concept of wave-particle duality, which states that particles such as electrons and photons can exhibit both wave-like and particle-like behavior depending on the experimental setup. This duality challenges the classical notion of particles as localized objects with definite positions and velocities.
Superposition and Quantum States: Quantum physics allows for the existence of superposition, where a quantum system can simultaneously exist in multiple states or locations. This is in contrast to classical physics, where a system is in a single, well-defined state. Superposition is a fundamental aspect of quantum mechanics and plays a crucial role in quantum computing and quantum information processing.
Measurement Problem: The measurement problem in quantum physics refers to the question of how and why a quantum system collapses from a superposition of multiple states into a definite state upon measurement. The process of measurement in quantum mechanics is not fully understood and remains a subject of debate and interpretation.
Quantum Entanglement: Quantum entanglement is a phenomenon in which two or more particles become correlated in such a way that the state of one particle cannot be described independently of the others. This non-local correlation, seemingly operating faster than the speed of light, challenges the principles of causality and locality in classical physics.
Compatibility with General Relativity: Classical physics is well-described by classical mechanics and general relativity, which provide a framework for understanding the behavior of objects in motion and the curvature of spacetime, respectively. However, quantum physics has not yet been successfully unified with general relativity, and developing a theory of quantum gravity that encompasses both quantum mechanics and general relativity is an ongoing challenge in theoretical physics.
These are some of the main issues and disparities between classical physics and quantum physics. Over the years, physicists have made significant progress in understanding and reconciling these differences, but some questions and challenges remain open, leading to ongoing research and exploration in the field of quantum physics.