I am talking about tree rings.
If you have ever seen the cross section of a tree you will know the rings I am talking about. just circles and circles of lighter and darker colour.
Great. So, trees have rings. So what?
Well, these rings are not just pretty looking rings. These rings can actually tell you something!
If you know how to count, you can detect how old a tree is! And this discipline, of dating trees using is called Dendrochronology. As I visited a lecture on it this year I thought I'd give you a little introduction to the topic, because tbh I have never heard of it before.
But don't go running off to the next tree, cut it down and start counting the rings. Firstly, there is a way to get this information without killing trees. By using a growth drill you can extract a core to use for counting the ring and the tree can happily continue growing. But there is something else you need to remember before running off to counting rings.
A year consists of a lighter ring followed by a darker ring. If you look really closely you might be able to tell that there is a harsh cut between dark and light wood, but the light wood goes smoothly over into the dark food. So the lighter coloured wood is the early wood, while the darker one is late wood. The sharp cut after the late wood is caused by, in our part of the world, winter. It is simply to cold for trees to grow. This growth break allows counting tree rings.
Depending on the surrounding conditions the growth rate can vary from year to year. An important aspect is weather. I won't go into to much detail, but basically if you have a tree cross section and you down know when this was cut you might be able to date the wood using weather information of the area from which the tree is from. This can actually help determine the building date of wooden houses.
Being able to date wood is also an important information when it comes to identifying wether a Rembrandt is real or fake. If the wood that has been painted on has been cut down 100 years after Rembrandt's death how could he have painted on it?
I hope this kind of made sense and you got a little idea about one of the many disciplines in Science. I hope I didn't bore you too much. I tried to keep as simple and basic, not drowning you in too many informations.
But I am always open for questions.