But that's not really how it is when scientists are working in their labs.
Let's consider the Flood and use what is called the "canopy theory." There is some evidence for a canopy surrounding the Earth before the Flood.
The canopy would probably not stop all the cosmic rays themselves, but a good deal of the scatter radiation would be reduced. Thus, there would be a few neutrons and fewer C-14 atoms formed.
Most of the carbon before the Flood would then be C-12.
Suppose the scientist doing the dating did not know about the Flood.
One also assumes that all the sand is in the bottom of the glass when one turns it over. He must look for something in the bone which disappears over time, as the sand disappeared from the top chamber of the egg timer.