A scientist who uses carbon 14 dating is measuring
The half-life refers to the amount of time it takes for half the radiocarbon in a sample of bone or shell or any carbon sample to disappear.
Libby found that it took 5568 years for half the radiocarbon to decay.
We know that it is older than Christendom, but whether by a couple of years or a couple of centuries, or even by more than a millenium, we can do no more than guess." [Rasmus Nyerup, (Danish antiquarian), 1802 (in Trigger, 19)].
He and two students first measured the "half-life" of radiocarbon.They used pottery and other materials in sites to date 'relatively'.