The question that often comes to our mind is how old is the earth and how do scientists know how old the earth is?
According to scientists, the world is actually like a big clock and we just need to know how to read this clock. To estimate the age of the earth, we need to think about what the world is made of.
The world, and everything in it, is actually made up of a very small thing called an “element”. These are small building blocks of everything. You may have heard the names of some elements before, such as gold is an element, and so is silver.
There are also many other elements with strange names like krypton and selenium and plutonium. As far as we know, there are about 118 different elements on Earth.
Most of these elements do not change and remain in their original state forever. Scientists call these elements “stable elements”.
But there is another element that changes over time into reality. They are not so common, but they are in everything. These are called “unstable” or “radioactive” elements.
Imagine that some part of you is actually turning into something else! But don’t worry, most of these changes are long overdue. Some quotes really take billions of years to make any serious change.
For example, your teeth contain an element called potassium, which is one of these changing elements. Almost everything, including your TV, computer, garden soil, has some of these changing elements. This process of change is called “radioactive decay”.
Similarly, rocks contain these volatile elements, and scientists have estimated how long it takes for one of these elements to transform into another.
For example, if we have something that has an unstable element called 14C (simply “carbon 14”), we know that half of all the 14C in our sample is made up of another element. It takes about 5,730 years to convert to 14N (called “nitrogen 14”).
Knowing how fast these elements change from one thing to another gives us a great indication of how old the earth is.
How to measure the age of the earth?
Scientists first measure how many unstable elements remain in the earth’s rocks (these are elements that have not yet changed into another element but will change over time because we know they are unstable).
Scientists then measure the amount of the element in which they change.
Once scientists know this, as well as how long this change takes, they can figure out how old the world is.
So how old is the earth?
Scientists have calculated that the age of the world is about 4,600,000,000 years, or 4.6 billion years.