So, we rely on radiometric *dating* to calculate their ages.

Radiometric **dating**, or **radioactive** **dating** as it is sometimes called, is a method used to date rocks and other objects based on the known decay rate of **radioactive** isotopes.

So, if you know the **radioactive** isotope found in a substance and the isotope's **half**-**life**, you can calculate the age of the substance. Well, a simple explanation is that it is the time required for a quantity to fall to **half** of its starting value.

**Half** **Life** is a characteristic of each **radioactive** isotope.

Depending on the isotope, its **Half** **Life** may range from a few fractions of a second to several billion years. The **Half** **Life** of Uranium-238 is 4,500,000,000 years.

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Free 5-day trial Radiometric **dating** is used to estimate the age of rocks and other objects based on the fixed decay rate of **radioactive** isotopes.

This web page from Break the Cycle lists useful resources for working with and in schools.

, but if you need help, you should be able to talk to a human.

This can be positive or negative depending on the nature of the community created.

Also, the 2007 Menu pet food tragedy that resulted in the deaths and severely compromised health of many cats and dogs left me with an even deeper desire to have as much control as possible over what goes into my cats’ food bowls.