Therefore if you count each light and dark ring to be one year you can work out how old the tree is. Scientists use a more accurate method of dating trees these days. It is called carbon dating. Carbon 14 is a radioactive isotope of carbon. It is produced in the upper atmosphere by radiation from the sun.
Trees get their carbon from carbon dioxide in the air.
So, some part of the carbon found in them will be C14. This C14 will undergo radioactive decay and the level of C14 left in a tree will tell us how old it is. You lose over 50 hairs a day from your head. About 50 hairs per day will fall out and after about 3 months a new hair will grow from that same hair follicle. No hair will last more than about 6 months.