Final answer:
Small amounts of radioactive materials like uranium and potassium in rocks act as natural clocks, allowing scientists to determine the age of rocks by measuring the decay rates of these isotopes. Atomic clocks, which use the vibrations of cesium atoms, are examples of how atoms can be used to keep precise time.
Step-by-step explanation:
Small amounts of radioactive materials in rocks can act as natural clocks. These materials, such as uranium and potassium, undergo radioactive decay at known, constant rates, which allows scientists to determine the ages of rocks and other nonorganic materials. The principle of using radioactive isotopes as natural clocks is based on measuring the decay of a parent isotope into a stable daughter isotope. As time passes, the amount of the parent isotope decreases while the amount of the daughter isotope increases. This decay process starts when the elements are first created and can be continuing until the material is analyzed.
For example, the decay of uranium into lead or the decay of potassium into argon are common methods used for this purpose. To date, the rocks accurately, the ratios of parent to daughter isotopes are compared, and from these, scientists can calculate the rock's age. This is because the half-life of each radioactive material, which is the time required for half of the substance to decay, is precisely known. By comparing how much of the parent element remains with how much of the daughter product has accumulated, it is possible to determine how long the decay process has been going on, and hence, the age of the rock.
Moreover, to achieve accurate results, modern timekeeping focuses on the atom. For instance, atomic clocks employ the vibrations of cesium atoms to maintain time with incredible precision. Such clocks rely on hyperfine transitions of the cesium atom, and these transitions are detected by monitoring the radiation emitted when cesium atoms transition between energy states.
Utilizing this incredible precision, the fundamental unit of time, the second, is defined by the frequency of these transitions in cesium atoms. These methods highlight how atomic and nuclear physics can be applied to practical and scientific endeavors, such as determining the age of Earth's materials and maintaining the most precise time standards.