Radioactive Dating

Because the radioactive half-life of a given radioisotope is not affected by temperature, physical or chemical state, or any other influence of the environment outside the nucleus that has no direct particle interactions with the nucleus, then radioactive samples continue to decay at a predictable rate. That is, any radioactive nucleus acts as a clock. If determinations or reasonable estimates of the original composition of a radioactive sample can be made, then the amounts of the radioisotopes present can provide a measurement of the time elapsed.

由于某种放射性同位素的半衰期不受温度、物理或化学状态，或任何其他环境因素的影响（这些因素没有与核发生直接的粒子相互作用），因此放射性样品继续以可预测的速率衰变。也就是说，任何放射性核都像一个钟表一样起作用。如果能够确定或合理估计放射性样品的原始组成，那么现有放射性同位素的量可以用来测量已流逝的时间。

One such method is called carbon dating, which is limited to the dating of organic (once living) materials. The longer-lived radioisotopes in minerals provide evidence of long time scales in geological processes. While original compositions cannot be determined with certainty, various combination measurements provide self-consistent values for the the times of formations of certain geologic deposits. These clocks-in-the-rocks methods provide data for modeling the formation of the Earth and solar system.

一种方法称为碳定年法，该方法仅适用于有机（曾经生活过的）物质的定年。矿物中半衰期较长的放射性同位素提供了地质过程中长时间尺度的证据。虽然原始成分无法确定，但各种组合测量提供了自洽的值，用于确定某些地质沉积物的形成时间。这些岩石中的钟表方法为模拟地球和太阳系的形成提供了数据。