  In 1904, while experimenting with high-speed photography, Lucien Bull
recorded a pellet passing through a soap bubble. We investigate the dynamics
that allow for a rigid body to pass through a hemispherical soap film without
rupturing it. In this fluid dynamics video spheres were dropped from rest above
a hemispherical soap film. At impact, the soap film stretches into a cavity
around the sphere. As the sphere continues to descend, the film cavity pinches
off and the film returns to its initial hemispherical shape. Upon closer
observation of the film-sphere-air interface, the stability of the soap film
appears to arise through a balance between the forces of the sphere inertia and
the film tension. Therefore the relevant experimental parameter is the Weber
number: We=rho*2*g*h*R*sigma, where R is the sphere radius and h is the height
that the sphere is dropped from. We vary the sphere radius and velocity to
provide a range of Weber numbers in order to investigate the dependence of film
stability. Three subtly distinct regimes arise across the observed experimental
range of Weber numbers. The first regime is demonstrated (We<3200) by a cavity
shape that resembles a catenoid which pinches off both near the sphere and the
hemispherical surface. The second regime is demonstrated (3200<We<6100) by a
uniformly narrowing cavity resembling an inverted cone that pinches off near
the sphere. The third regime initially appears similar to the second but the
greater sphere inertia (6100<We) elongates the cavity shape and causes
pinch-off and cavity collapse to be non-uniform in nature.
