Textbook Definition: Wheeler’s Delayed Choice Experiment is a thought experiment (later realized in actual experiments) that demonstrates the bizarre nature of quantum reality. In this experiment, the decision to measure which path a photon takes through a double-slit apparatus is delayed until after the photon has already passed through the slits. Surprisingly, this delayed choice still determines whether the photon behaved as a particle or a wave earlier in its journey, seemingly affecting the past.

Simplified for Glossary: An experiment where a measurement made after a particle has passed through a barrier appears to retroactively determine whether it behaved as a wave or particle, challenging our understanding of cause and effect.

Ring 2 — Canonical Grounding

Ring 3 — Framework Connections

Canonical Hub: CANONICAL_INDEX