from a chemistry class a few years ago was entropy. Atoms will eventually rearrange themselves to a low-energy state, given the right conditions. The better the conditions, the quicker the decay.
In the real world (apologies to Plato) Leave a metal structure, a jump ramp, for example, sitting in water long enough, and it will rust. If it is heavy and it has rusted through, it will break. Have eight people stand on the back of the ramp to reduce tongue pressure on Pat's trailer hitch and it will break right away. After an all-around expletive session, discussion veered toward topics like angle iron, stick welding, and numeric references to voltages and thickness of steel.
All I know about welding is that it's a great way to put an eye out. If Pat emails me, I'll have pictures soon.
Because jumping is rife with suspense, and narrow time windows, we have only until april 7th, when we host a collegiate tournament at our site.