The tree looks like a petrified ogre caught in the act of eating chains. Like an ogre who might guard a bridge and when you try to pass asks you a math problem in a voice that sounds like he’s gargling gravel. If you answer correctly you will hear him say, “You may pass.” Get it wrong and you’ll hear your bones crunch in his chain-eating jaws.
You pound a nail into a tree three feet off the ground. If the tree grows 1.79 feet per year, how high up will the nail be in 4 years and 36 days (0.008 years)?
You have one minute to solve it.
The answer is three feet. Did you find yourself in the ogre’s mouth on the other side of the bridge?
The ogre was testing your 8th grade science knowledge. The reason the nail stays at the same height is because trees add layers at the top, not at the bottom. A tree grows taller from the apical meristem at the tips of branches and trunks. Roots elongate the same way, they add tissue at their tips. This is why a barbed wire fence nailed to a tree thirty years ago isn’t 20 feet in the air today. Or why those initials you and your wife carved into that oak tree saying you’ll be together forever in 1998 is still at eye level and why you now have to walk your new wife hurriedly past that tree hoping she doesn’t notice. But wait long enough and maybe the lateral meristem will cover your shame.
Trees grow taller from the tips and fatter from the outer layers. Stem and trunk diameters increase each year as a new layer of wood is wrapped around the tree. This is why – after a while – a tree looks like its chewing on barbed wire or old dog chain left behind by former tenants. The barbed wire stayed in place as the new layers grew past it.