Half lives used carbon dating fossils rocks
Understand how decay and half life work to enable radiometric dating.
Play a game that tests your ability to match the percentage of the dating element that remains to the age of the object.
Imagine that you enjoy a certain kind of ice cream flavored with chocolate chips.
Sure, you can scour the Internet and learn rather quickly that the scientific consensus pins the age of of the planet at about 4.6 billion years.
But Google didn't invent this number; instead, human ingenuity and applied physics have provided it.
You also need to know when you can or cannot apply a particular type of device to the task at hand; for example, if you want to know how hot it is on the inside of an active wood stove, you probably understand that putting a household thermometer intended to measure body temperature inside the stove is not going to prove helpful.
Be aware also that for many centuries, most human "knowledge" of the age of rocks, formations such as the Grand Canyon, and everything else around you was predicated on the Genesis account of the Bible, which posits that the entire cosmos is perhaps 10,000 years old.