Using publicly available video of a diffusion cloud chamber with a very small
radioactive source, I measure the spatial distribution of where tracks start, and consider possible
implications. This is directly relevant to the quantum measurement problem and its possible
resolution, and appears never to have been done before. The raw data are relatively uncontrolled,
leading to caveats that should guide future, more tailored experiments. Results may suggest a
modification to Born’s rule at very small wavefunction, with possibly profound implications for
the detection of extremely rare events such as proton decay. I introduce two candidate smallwavefunction
Born rule modifications, a hard cutoff and an offset model; the data may favor the
offset model, which has a stronger underlying physical rationale. Track distributions from decays
in cloud chambers represent a previously unappreciated way to probe the foundations of quantum
mechanics, and a novel case of wavefunctions with macroscopic signatures.