Question

What is the age of the earth and how do we know this?

Answer 1

Earth is the only planet in the solar system which has life in it. It does not have any records of how old it is and therefore it is quite difficult to find out its real age. Over the past $400$years, scientists have made several attempts to date the planet. Based on changing sea levels, the time it took to cool to the current temperature for the earth or sun. So let us see how old the earth is and how scientists found this?

Complete answer:
Scientists made another effort to calculate the age of the earth; they turned their attention to rocks that cover the surface. Finding the oldest piece of rock and then figuring out how old it is conceptually straightforward. However, practically it is difficult to find the oldest rock. This is due to plate tectonics. This process makes the earth constantly recycle its rock. But still, the oldest rock that is found on the Earth has been named a tiny piece of zircon and it is found in Western Australia.
The scientific technique known as radiometric dating is the process to find out the age of the rock. This process is about the ratio between the number of carbon- $14$ and carbon- $12$ in any once-living being. This ratio tells us how long it’s been since that being was alive. Based on this technique that is used on the oldest rock zircon, we came to the conclusion that the Earth is at least $4.374$ billion years old.

Note:
But scientists say that it can be a bit older than this. That is approximately $4.54$ billion years old. Plate tectonics is a process in which the Earth’s outer shell is further divided into several plates, maximum and minimum plates that usually slide over the mantle. These plates act like a solid rigid shell compared to Earth’s mantle. The rigid outermost shell of the earth is called a lithosphere and this is broken up into tectonic plates.