# Casimir's Effect (DD-618) > In 1948 the Dutch physicist Hendrik Casimir predicted that two uncharged, parallel conducting plates in a vacuum would be pushed together. In quantum theory, the vacuum is not empty but full of fluctuating electromagnetic fields. The plates limit which field modes fit between them, so the pressure outside is greater than the pressure inside. The force is tiny and only matters at very small separations. Steven Lamoreaux measured it directly in 1997, at gaps of 0.6 to 6 micrometers, agreeing with theory to within about 5%. Engineers now consider it in the design of micromachines (MEMS). The dynamic version, which is what the Reel describes, was proposed by Gerald Moore in 1970. A mirror moving at a significant fraction of the speed of light could convert virtual photons into real, detectable ones. Moving a physical mirror that fast isn't practical. In 2011, Christopher Wilson and colleagues at Chalmers University of Technology in Sweden instead used a superconducting circuit, published in Nature. A SQUID (superconducting quantum interference device) changed the electrical length of a transmission line about 11 billion times a second, at an effective speed of a few percent of light speed. They detected microwave photons emitted in correlated pairs, the predicted signature, and called it the first observation of the dynamical Casimir effect. The footage shows two metal strips hanging side by side and drawing together. That's a visible-scale stand-in for illustration: real Casimir forces are only measurable at micrometer gaps. - Department: Science - First published: 2025-07-20 - Last updated: 2025-07-20 - Permalink: https://detailenjoyer.com/case/casimirs-effect/ - Author: Marcus Easterling (DetailEnjoyer), The Detail Department ## Quick facts - **DD-618-F01**: Hendrik Casimir predicted the Casimir force in 1948. _(Write-up · Exhibit A (The static effect))_ - **DD-618-F02**: The dynamical Casimir effect was first observed in 2011 in a superconducting circuit. _(Write-up · Exhibit A (The static effect))_ ## Write-up Photons from empty space. In 2011 a superconducting circuit turned vacuum fluctuations into real light. 1. **The static effect**: Casimir predicted in 1948 that uncharged conducting plates in a vacuum would attract. 2. **Measured**: Lamoreaux measured the force in 1997 at gaps of 0.6 to 6 micrometers, within about 5% of theory. 3. **Moving mirrors**: In 1970, Moore proposed that a mirror moving near light speed could turn virtual photons into real ones. 4. **A circuit as mirror**: Chalmers researchers used a SQUID to change a circuit's electrical length at a few percent of light speed. 5. **Photons in pairs**: They detected photons emitted in correlated pairs, the signature of the dynamical effect. ## Related case files - [Alcubierre Drive (DD-060)](https://detailenjoyer.com/case/alcubierre-drive/): Warp-drive proposals often cite Casimir-type negative energy - [Quantum Infrastructure (DD-012)](https://detailenjoyer.com/case/quantum-cryogenics/): Another case about superconducting quantum circuits ## Reel vs. record - **Note**: 'Accelerating or moving mirrors': only a mirror moving at a significant fraction of light speed produces measurable photons. The first observation (Chalmers, 2011) used a superconducting circuit whose electrical length changed at a few percent of light speed. - **Note**: 'Real particles, such as photons': the Chalmers experiment detected microwave photons emitted in correlated pairs, the predicted signature. - **Note**: 'A force between stationary conducting plates': the static force is tiny and only measurable at very small gaps. Lamoreaux measured it in 1997 at 0.6–6 micrometers. - **Note**: 'Virtual particles become actual': that's the standard popular description. Wilson et al. describe it as converting virtual photons into directly observable real photons. - **Missing**: Hendrik Casimir predicted the static effect in 1948, and Gerald Moore proposed the dynamical version in 1970. ## Video: Casimir's Effect: Photons From Empty Space - Duration: 24.5 s · Published: 2025-07-20 - File: https://detailenjoyer.com/assets/videos/DMUephLt1ml.mp4 ### Transcript DID YOU KNOW? The dynamic Casimir effect is a quantum phenomenon where accelerating or moving mirrors, or boundaries in a vacuum can create real particles, such as photons, from the vacuum's fluctuating electromagnetic field. Unlike the static Casimir effect, which produces a force between stationary conducting plates due to vacuum fluctuations, the dynamic version involves changing boundary conditions rapidly enough that virtual particles become actual, detectable particles. NOW YOU KNOW! ## Questions & answers **Q: When did Hendrik Casimir predict the Casimir force?** A: With conducting plates in a vacuum. _(Source: Write-up · Exhibit A (The static effect) · arXiv: Wilson et al., Observation of the Dynamical Casimir Effect in a Superconducting Circuit (1105.4714); Wikipedia: Casimir effect)_ **Q: In the static Casimir effect, what happens to two uncharged parallel plates?** A: Pressure outside exceeds pressure between them. _(Source: Write-up · Exhibit A (The static effect) · arXiv: Wilson et al., Observation of the Dynamical Casimir Effect in a Superconducting Circuit (1105.4714); Wikipedia: Casimir effect)_ **Q: Where was the dynamical Casimir effect first observed?** A: Published in Nature in 2011. _(Source: Write-up · Exhibit B (Measured) · Lamoreaux (1997), Demonstration of the Casimir Force in the 0.6 to 6 μm Range, Physical Review Letters; Wikipedia: Casimir effect)_ **Q: What device stood in for the moving mirror?** A: It changed the circuit's electrical length. _(Source: Write-up · Exhibit B (Measured) · Lamoreaux (1997), Demonstration of the Casimir Force in the 0.6 to 6 μm Range, Physical Review Letters; Wikipedia: Casimir effect)_ **Q: At what gaps did Lamoreaux measure the Casimir force?** A: In 1997. _(Source: Write-up · Exhibit A (The static effect) · arXiv: Wilson et al., Observation of the Dynamical Casimir Effect in a Superconducting Circuit (1105.4714); Wikipedia: Casimir effect)_ ## Sources - [Wilson et al. (2011), Observation of the dynamical Casimir effect in a superconducting circuit, Nature](https://doi.org/10.1038/nature10561) - [arXiv: Wilson et al., Observation of the Dynamical Casimir Effect in a Superconducting Circuit (1105.4714)](https://arxiv.org/abs/1105.4714) - [Lamoreaux (1997), Demonstration of the Casimir Force in the 0.6 to 6 μm Range, Physical Review Letters](https://doi.org/10.1103/PhysRevLett.78.5) - [Wikipedia: Casimir effect](https://en.wikipedia.org/wiki/Casimir_effect) ## Cite this case file Easterling, Marcus. "Casimir's Effect." The Detail Department (DetailEnjoyer), case file DD-618, last updated Jul 20, 2025. https://detailenjoyer.com/case/casimirs-effect/