However, there were also properties that could not be explained, including the non-spherical distribution of charge in certain nuclei. In a 1950 paper, James Rainwater of Columbia University suggested a variant of the drop model of the nucleus that could explain a non-spherical charge distribution. Rainwater's model postulated a nucleus like a balloon with balls inside that distort the surface as they move about.
The non-spherical distribution of charge in certain nuclei was a challenge to understanding nuclear structure, and James Rainwater's 1950 paper offered an explanation through his model of a nucleus resembling a balloon with balls inside that would distort the surface as they moved about.