While it might sound like science-fiction, the idea that the Universe is embedded in a broader multidimensional space is something that cosmologists have been pondering. The cosmos might exist in parallel with outer universes in other sets of dimensions. These universes are called braneworlds. If this is an accurate description of what’s happening, then the Universe could end up inside another one.
A few years ago, Michael Sarrazin of the University of Namur in Belgium and his colleagues showed how baryonic matter might make the leap into other universes in the presence of large magnetic potentials. This has provided a theoretical basis for matter swapping.
Today, Sarrazin et al. believe that our galaxy might provide a large enough magnetic potential for this to occur. If this is the case, then it’s conceivable that this phenomenon can be observed in a laboratory setting. Some experiments, involving trapping ultracold neutrons in bottles at L’Institut Laue-Langevin in Grenoble, France and the Saint-Petersburg Institute of Nuclear Physics, are already underway which might prove an inkling on how this could happen.
Ultracold neutrons move so slowly that it’s possible to trap them in bottles that are made up of magnetic fields. The rate of the neutron decay could be partially explained by the result of neutrons jumping from our universe into another. Sarrazin has measured this probability, and it’s about one in a million. This doesn’t confirm whether actual matter swapping takes place, only that when it does, it doesn’t happen very often.
According to some of their theoretical work, if there is a change in the gravitational potential, it should also affect the rate of matter swapping. If they carry out a neutron trapping experiment that lasts a whole year, long enough for the Earth to complete at least one revolution around the sun, and if the decay rate varies, then that could be a strong indication that matter swapping is actually occurring.
Reference: “Experimental limits on neutron disappearance into another braneworld” by Michaël Sarrazin, Guillaume Pignol, Fabrice Petit and Valery V. Nesvizhevsky, 30 April 2012, Physics Letters B.