We could put forward the following counter arguments to the constancy of these assumptions: a) The constancy of cosmic ray bombardment might be questioned.
The current high rate of entry might be a consequence of a disturbed post-Flood environment that altered the .
A rock sample from Nigeria was dated at 95 million years by the potassium-argon method, 750 million years by the uranium-helium method, and less than 30 million years by the fission-track method.
If the clock is not set to zero when a deposit forms, then there can be no starting point from which to calculate the age of a deposit.
Many examples from literature show that the zero-reset assumption is not always valid.
Volcanic ejecta of Mount Rangitoto (Auckland, New Zealand) was found to have a potassium-40 age of 485,000 years, yet trees buried within the volcanic material were dated with the carbon-14 method to be less than 300 years old.
If even a small percentage of the limestone deposits were still in the form of living marine organisms at the time of the Flood, then the small amount of carbon-14 would have mixed with a much larger carbon-12 reservoir, thus resulting in a drastically reduced ratio.
They will argue that the clock was not reset if the age is too old, or that isotopes were selectively removed if the age turns out to be too young.
In the study on the Hawaii lava flow cited above, it was argued that entrapment of excessive amounts of argon gas had made the samples appear older than they were.
Some scientists argue that the magnetic field of the earth has declined over time.
c) Atmospheric carbon forms just 0.0005% of the current carbon reservoir—99.66% of the earth's carbon exists in limestone, 0.31% in oil and gas, and 0.02% in coal.