Related Experiment Video
Updated: Sep 26, 2025

In Situ Measurement of Vacuum Window Birefringence using 25Mg+ Fluorescence
Published on: June 13, 2020
There Is No Spooky Action at a Distance in Quantum Mechanics
1Departments of Astronomy and Physics, Haverford College, Haverford, PA 19041, USA.
Abstract:
Einstein became bothered by quantum mechanical action at a distance within two years of Schrödinger's introduction of his eponymous wave equation. If the wave function represents the "real" physical state of a particle, then the measurement of the particle's position would result in the instantaneous collapse of the wave function to the single, measured position. Such a process seemingly violates not only the Schrödinger equation but also special relativity. Einstein was not alone in this vexation; however, the dilemma eventually faded as physicists concentrated on using the Schrödinger equation to solve a plethora of pressing problems. For the next 30 years, wave function collapse, while occasionally discussed by physicists, was primarily a topic of interest for philosophers. That is, until 1964, when Bell introduced his famous inequality and maintained that its violation proved that quantum mechanics and, by implication, nature herself are nonlocal. Unfortunately, this brought the topic back to mainstream physics, where it has remained and continues to muddy the waters. To be sure, not all physicists are bothered by the apparent nonlocality of quantum mechanics. So where have those who embrace quantum nonlocality gone wrong? I argue that the answer is a gratuitous belief in the ontic nature of the quantum state.
Related Concept Videos
The de Broglie Wavelength
The Quantum-Mechanical Model of an Atom
The Uncertainty Principle
The Pauli Exclusion Principle
The Bohr Model
Space-Time Curvature and the General Theory of Relativity
This has been verified in many experiments. However, space and time are no longer absolute. Two observers moving relative to one another do not agree on the length of objects or the passage of time. The mechanics of objects based on Newton's laws of...

