Local realism

Definition

Local realism is a philosophical concept in quantum mechanics that asserts two key ideas: physical processes occur locally, meaning that information cannot travel faster than the speed of light, and objects possess definite properties independent of measurement. This viewpoint is significant because it contrasts with the phenomena observed in quantum entanglement, which challenges the notion that local hidden variables can fully explain the behavior of entangled particles.

5 Must Know Facts For Your Next Test

1. Local realism combines two key principles: locality (no faster-than-light influence) and realism (properties exist prior to measurement).
2. In experiments testing Bell's theorem, violations of local realism have been observed, suggesting that particles can behave in ways not compatible with local hidden variable theories.
3. Local realism was a common viewpoint among physicists until experiments demonstrated entanglement phenomena that could not be explained by this perspective.
4. The debate between local realism and the predictions of quantum mechanics is central to discussions on the interpretation of quantum theory.
5. Local realism challenges the classical intuitions about the separability and independence of distant objects, leading to philosophical implications about the nature of reality.

Review Questions

• How does local realism conflict with the phenomenon of quantum entanglement?
  • Local realism asserts that physical processes occur locally and that objects have definite properties independent of measurement. However, quantum entanglement demonstrates that particles can be correlated in such a way that measuring one particle instantaneously affects the other, regardless of distance. This suggests that either locality or realism must be sacrificed, as entangled particles behave in ways that defy these classical intuitions.
• Discuss the implications of Bell's theorem on the concept of local realism and its acceptance in the scientific community.
  • Bell's theorem shows that no local hidden variable theories can fully replicate all predictions made by quantum mechanics. This has profound implications for local realism because it indicates that either our understanding of locality or realism must be revised. Many experimental tests have supported Bell's theorem, leading to a decline in support for local realism within the scientific community as more researchers accept nonlocal interpretations of quantum phenomena.
• Evaluate the philosophical consequences of abandoning local realism in light of quantum mechanics' predictions.
  • Abandoning local realism forces a reevaluation of fundamental concepts about reality and causality. If nonlocality is accepted, it implies instantaneous connections between distant particles, challenging our classical understanding of space and time. This shift leads to deeper questions about determinism and the nature of information in the universe, as well as what it means for an object's properties to exist independently of observation. Such philosophical consequences encourage ongoing discourse about how we perceive and understand reality at a quantum level.

Related terms

Quantum Entanglement:

A phenomenon where particles become interconnected in such a way that the state of one particle instantly influences the state of another, regardless of the distance separating them.

Bell's Theorem: A fundamental result in quantum mechanics that demonstrates that no local hidden variable theories can reproduce all the predictions of quantum mechanics, suggesting that either locality or realism must be abandoned.

Nonlocality: The idea that objects can instantaneously affect one another's state, regardless of distance, which contradicts the principles of local realism.