There are over forty such techniques, each using a different radioactive element or a different way of measuring them.
It has become increasingly clear that these radiometric dating techniques agree with each other and as a whole, present a coherent picture in which the Earth was created a very long time ago.
Some things are very obvious such as non-original or reconed speakers, non-original transformers, replaced pots, re-tweed, re-tolex, re-grill, etc.
The passage of time can be charted by the reduction in the number of parent atoms, and the increase in the number of daughter atoms.
For example, most people don't realize that carbon dating is only rarely used on rocks. A disagreement over the age of the Earth is relatively minor in the whole scope of Christianity; it is more important to agree on the Rock of Ages than on the age of rocks.
But because God has also called us to wisdom, this issue is worthy of study.
Assuming a strictly literal interpretation of the week of creation, even if some of the generations were left out of the genealogies, the Earth would be less than ten thousand years old.
Radiometric dating techniques indicate that the Earth is thousands of times older than that--approximately four and a half billion years old.