Do you know age of a tree planted around you?
As a tree grows, its trunk thickens as new wood is added in the middle of the trunk.
The age of a tree can be judged not only by the thickness and height of a tree but also by the number of circles on the trunk. Each circle indicates roughly a year.
In fact if find any severed tree you will see number of concentric circles in a cross section of trunk growing from the middle outwards. The space between two concentric circles represent annual layer of wood and by counting number of circles themselves the age of a tree can be known.
If you count number of circles in some giant fir trees, it will be many hundreds of years old.
These circles are also known as tree’s rings.