These processes involve sampling rocks and determining how old they are from their rate of decay.
We have a long record of events in absolute time but much of that occurred before humans were on Earth to write it down.
So instead of human records, geologists use techniques such as radiometric dating.
Absolute dating is the process of determining a specific date for an archaeological or palaeontological site or artifact.
Some archaeologists prefer the terms chronometric or calendar dating, as use of the word "absolute" implies a certainty and precision that is rarely possible in archaeology.
For example, a rock layer that is below another one is older and we know this even without knowing how old the rocks are simply by their position relative to each other.
Just like we know that dinner comes after lunch even though we may not know what time it occurs.
And when we put both absolute and relative time together we create a geologic time scale that puts all these events in perspective. are layered in their relative order from oldest at the bottom to most recent at the top, and we also see how much absolute time each one spans.
For example, if we look at the scale we see that the Paleozoic Era comes before the Mesozoic Era, relatively speaking, and that it spans about 290 million years (starting about 542 million years ago and ending about 251 million years ago).
Before the advent of absolute dating in the 20th century, archaeologists and geologists were largely limited to the use of relative dating techniques.
It estimates the order of prehistoric and geological events were determined by using basic stratigraphic rules, and by observing where fossil organisms lay in the geological record, stratified bands of rocks present throughout the world.
You may not think about time too much but geologists think about it a lot.