Although the possible connection between electrostatic and intermolecular forces was used by Lorentz as a plausibility argument, the contraction hypothesis was soon considered as purely ad hoc. It is also important that this contraction only affected the space between the electron but not the electrons themselves, therefore the name "intermolecular hypotheses" was sometimes used of this effect. The so-called Length contraction without expansion perpendicularly to the line of motion and by the precise value (where l0 is the length at rest in the ether) was given by Larmor in 1897 and by Lorentz in 1904.