Comment on ``Precision measurement of the Casimir-Lifshitz force in a fluid''

TL;DR

This paper critically examines a recent experiment measuring the Casimir force in ethanol, revealing significant discrepancies and unaccounted forces that question the experiment's claimed precision and agreement with theory.

Contribution

It provides a detailed critique of the experimental and theoretical methods used, highlighting errors and omissions that affect the validity of the original results.

Findings

Discrepancy of up to 25% in Casimir force calculations

Underestimation of electrostatic forces by a factor of 590

Neglect of charge double layer interactions

Abstract

Recently J.N. Munday and F. Capasso [Phys. Rev. A {\bf 75}, 060102(R) (2007); arXiv:0705.3793] claimed that they have performed a precision measurement of the Casimir force between a sphere and a plate coated with Au, both immersed in ethanol. The measurement results were claimed to be consistent with the Lifshitz theory. We demonstrate that the calculation of the Casimir force between the smooth bodies following the authors prescription has a discrepancy up to 25% with respect to authors result. We show also that the attractive electrostatic force only due to the surface potential differences was underestimated by a factor of 590 and the charge double layer interaction was not taken into account. All this leads to the conclusion that the results of this experiment are in fact uncertain.