Isotope carbon used dating things archaeology
Thus, he concluded, if our Earth were older than 30,000 years the incoming water should just equal the water leaking out.
The half-life of a radioactive isotope describes the amount of time that it takes half of the isotope in a sample to decay.
The argument may be compared to filling a barrel which has numerous small holes in its sides.
We stick the garden hose in and turn it on full blast.
The water leaking out the sides of the barrel represents the loss (mainly by radioactive decay) of the atmosphere's supply of carbon-14.
Now, the fuller that barrel gets the more water is going to leak out the thoroughly perforated sides, just as more carbon-14 will decay if you have more of it around.