How a Calcium Nucleus Turns into Titanium
The calcium-48 nucleus is like a locked room with 48 nucleons inside. Rearrangements are happening within: a neutron turns into a proton, and the room slowly rebuilds itself into another — titanium-48. The process takes an unimaginably long time: on average, a trillion trillion years, but it does happen.
To describe such a rearrangement, physicists assembled the nuclear wavefunction from pieces.