Jon G.

A tree grows each year and leaves concentric rings on a cross section of its
trunk. Logs are sawn into lumber so the rings make the best lumber. A
board is cut with the face of the board tangent , perpendicular, or at some
angle to the rings. Tangent rings displays more beauty and splits less, but
is weaker. Perpendicular rings are stronger but split more.

Tangent rings create a grain on the face of the board of nested parabolas.
When a hand plane is used on the face, the wood has to be planed towards the
trough of the parabola, or the plane blade catches and splits. This is one
principle every woodworker knows, or finds out quick the hard way.

It is ironic that as wood becomes more scarce, woodworking tools have grown
exponentially better. Where were these wood crafting wonder tools in the
old days of hand tools when wood was abundant and supply exceeded demand?
Chemical engineers need to take a hard look at wood and come up with
something similar, made out of something cheap and abundant, like dirt.
When oil runs out, there goes plastics as well.