We found this shelter half way up Rake Beck on Great Borne. It looks like an old Cumbrian grouse butt. That's Ennerdale Water in the background. It reminded me of the potential well for alpha particles escaping from a nucleus.
The idea of a potential well is an analogy: energy is needed to remove a ball from a well by doing work against the attractive force of gravity and this can be a model of removing an alpha particle from the nucleus by doing work against the strong nuclear force. This potential well sticks out above ground level because moving alpha particles from outside towards the nucleus results in energy being stored because of work done against repulsion. This is like going uphill. The weird thing that can happen is that alpha particles inside the nucleus can tunnel out through the walls.This is called quantum tunneling. It would be like sitting inside the grouse butt and suddenly appearing sat outside without climbing out.
