Measurement of the Casimir Force between Parallel Metallic Surfaces
G. Bressi · G. Carugno · R. Onofrio · G. Ruoso
Abstract and summary · read the original at the source
In one page
Hendrik Casimir predicted in 1948 that two flat conducting plates facing each other in empty space would be pushed together by the vacuum itself, because the gap between them can hold fewer field modes than the space outside. For half a century that force was only measured in an easier geometry, a sphere against a plate. Giovanni Bressi, Giovanni Carugno, Roberto Onofrio and Giuseppe Ruoso, working at Italy’s Legnaro national laboratory, did it the way Casimir described it. They faced a chromium-coated silicon cantilever against a matching rigid surface, held the two parallel to better than thirty nanometres across more than a millimetre, cancelled the stray contact voltage, and then watched the cantilever’s resonant frequency shift as the gap closed. Between half a micrometre and three micrometres the frequency shift followed the predicted law, and the force coefficient came out at 1.22 plus or minus 0.18 times ten to the minus twenty-seven newton metres squared — Casimir’s number, measured to 15 percent.
Why it matters hereChapter 2 rests on the fact that the vacuum is a real medium you can push on, and this is that fact measured in the exact configuration Casimir wrote down, with a different apparatus and a different laboratory from Lamoreaux and from Mohideen. It reaches chapter 3 through the authors’ own closing point: the same vacuum energy that moves their cantilever is the energy that has to be reconciled with how the Universe expands.
What it claims
01Summing all the vacuum mode contributions for an indefinite plane cavity of conducting material gives a quantum vacuum pressure equal to a coefficient divided by the fourth power of the gap, where that coefficient is pi times the Planck constant times the speed of light divided by 480, about 1.3 times ten to the minus twenty-seven newton metres squared.Opening section, the definition of the coefficient K sub C
Settled physics02The measured coefficient is 1.22 plus or minus 0.18 times ten to the minus twenty-seven newton metres squared, in agreement with the value Casimir first evaluated, giving the force between parallel conducting surfaces in the range half a micrometre to three micrometres at the 15 percent precision level.Equation 4 and the sentence following it
Settled physics03The sign of the fitted coefficient confirms the force is attractive, and leaving the distance exponent free in the fit returns 5.0 plus or minus 0.1, exactly what the dynamical component of the Casimir force between parallel surfaces should give — the force itself scaling as the inverse fourth power of the gap.Figure 4 caption
Settled physics04Before this work the parallel-plate configuration, the situation Casimir originally discussed, had only been attempted once, by Sparnaay in 1958, whose data did not contradict the prediction but carried large systematic errors and uncontrolled electrostatic forces; the sphere-against-plate geometry had reached 1 percent, with further precision limited by the theoretical uncertainty of the proximity force theorem.Introduction, the survey of previous attempts
Settled physics05The authors state the reach of the result themselves: it unambiguously shows the existence of quantum fluctuations at the macroscopic level, and confirms that there is a delicate issue in matching quantum physics to the large-scale evolution of the Universe through the cosmological constant.Concluding paragraph
What to watch06A deviation from the fitted curve appears systematically in the one to two micrometre region, which the authors attribute to conventional candidates — border effects, residual surface roughness, the finite conductivity of chromium, finite temperature corrections — and they say work is in progress to handle it, because the parallel-plate geometry maximises sensitivity to new forces of near-gravitational strength below the millimetre range and could set stronger constraints than the sphere-plate results.Paragraph following Equation 4, and Figure 4 caption
What to watch
Read it · abstract
Abstract
We report on the measurement of the Casimir force between conducting surfaces in a parallel configuration. The force is exerted between a silicon cantilever coated with chromium and a similar rigid surface and is detected looking at the shifts induced in the cantilever frequency when the latter is approached. The scaling of the force with the distance between the surfaces was tested in the 0.5 to 3.0 micrometre range, and the related force coefficient was determined at the 15 percent precision level.
The way in
https://doi.org/10.1103/PhysRevLett.88.041804Published as Physical Review Letters 88, 041804 (2002), under the APS default licence. The preprint is on arXiv as quant-ph/0203002, posted 1 March 2002 under the arXiv.org perpetual non-exclusive licence, which does not grant redistribution — checked on the arXiv record for this paper on 2026-09-08, where no Creative Commons statement appears. So this page carries the summary, the claims and the authors’ own abstract and sends the reader to the source. The claims below are read against that preprint. The work was done at the Laboratori Nazionali di Legnaro of the Istituto Nazionale di Fisica Nucleare, with the authors at INFN Pavia, INFN Padova and the Galileo Galilei physics department of the University of Padova.
How to cite it
G. Bressi, G. Carugno, R. Onofrio, G. Ruoso (2002) Measurement of the Casimir Force between Parallel Metallic Surfaces. doi:10.1103/PhysRevLett.88.041804
Where it sits in the curriculum