Liquid lens dynamics and fusion on a soap film: toward cosmology analogues?

The analogy of marbles orbiting on spandex is widely used to provide an accessible, visual representation of how massive objects warp spacetime in general relativity. While the analogy is very limited, this system still is of interest to study orbiting bodies [American Journal of Physics, 2001, Vol. 70, No. 1, pp. 48–52]. Yet an inherent drawback of this setup is the solid nature of the involved masses, which prevent them from exhibiting complex merging dynamics when they meet at the center of the fabric, as one may witness in the merging of large cosmological structures, such as galaxies. In this work we study the dynamics of droplet deposited on a horizontal soap film. The deposition of drops results in local distortions of the film, which remain stable for minutes and are here called lenses. As in the case of spandex, multiple lenses with initial velocities will attract each other leading to orbiting dynamics. But the fluidic nature of the lens also enables to observe their mutual deformation action at short range, followed by complex fusion dynamics reminiscent of galaxy merging simulations. In this presentation we will introduce our current understanding of this system.