We can get absolute ages only if we have rocks from that surface.
For others, all we are doing is getting a relative age, using things like the formation of craters and other features on a surface.
Radioactive decay involves the spontaneous transformation of one element into another.
The only way that this can happen is by changing the number of protons in the nucleus (an element is defined by its number of protons).
In part, they measure the age of rocks and other natural materials by dating techniques.
They can date rocks by gauging the amount of decay of radioactive elements.
This decay is an example of an exponential decay, shown in the figure below.
Geologists use a dating technique called K-Ar geochronology to find the age of layers of volcanic ash in ice cores. By measuring the ratio of K to Ar in feldspar crystals in volcanic ash, geologists can determine the time of the eruption and, thus, the age of ice in which the ash is found. Heating causes the kernels to begin popping, thereby starting your simulated “radioactive decay clock” and producing popped “daughter” popcorns.
Once they determine the age of a volcanic ash layer, geologists can study the materials in that ice core layer for clues about climate conditions at that time. The half-life of your kernel-popcorn material is the time necessary for half of the given kernels to become popcorns.
Radioactivity and radioactive decay are spontaneous processes.
Scientists look at half-life decay rates of radioactive isotopes to estimate when a particular atom might decay.
A useful application of half-lives is radioactive dating.