Geologist Kevin Henke has criticised Humphreys for stating that "zircons from the Fenton Hill rock cores... contain too much radiogenic helium to be billions of years old." Henke wrote that the equations in Humphreys' work "are based on many false assumptions (isotropic diffusion, constant temperatures over time, etc.) and the vast majority of Humphreys "et al."'s critical "a", "b", and "Q"/"Q0" values that are used in these 'dating' equations are either missing, poorly defined, improperly measured or inaccurate." Humphreys has replied to Henke's criticisms. Henke subsequently refuted the response. Scientists Glenn Morton and George L Murphy have dismissed Humphreys' idea that the Earth is cooling as "wrong" because "it is ineffective, it is falsified by observational data, and it is theologically flawed."