One of the most fundamental theoretical problems in physics today could be explained in other ways without using string theories. The black holes, the weird objects that triggered this scientific debate, could actually contain a fully developed infinite universe, into a finite space, thus eliminating the illusive and problematic singularity.

As we all know, black holes are objects of extreme mass - the smallest ever recorded had only the mass of 3 times that of the Sun, with some special features including extreme gravitational pull on its surface, and the fact that in the absence of large gas clouds to feed on, they practically give off no radiation, resembling the features of the theoretical black body, thus making them incredibly hard to find.

They are surrounded by a so-called event horizon, which determines the maximum distance at which you can approach a black hole, without being pulled into it by its powerful gravity. Any object passing the event horizon will ultimately have no chance of ever escaping its final fate of hitting the ultra dense singularity. As you can see in the picture, the massive spherical object in the middle represents the event horizon, and is depicted in black because not even light can escape once it enters it, thus nobody will ever see the singularity. The singularity is a two dimensional ultra dense object, of zero volume.

The problem of physics today is that there is no known theory that can explain such an object, Einstein's Theory of General Relativity and the quantum physics just do not work together at such a level.

Instead of explaining the singularity, the scientist are trying to come up with a model that would completely eliminate it. Objects that get swallowed by a black hole, probably fall through a wormhole-like connection into another universe, the interior becoming a universe of its own. This is called a Nariai universe, in which space expands in only one direction allowing an object to travel through it forever.

Other theories propose a solution in which an object falling into a black hole would end up in a two-mouthed black hole, and will oscillate back and forth inside it forever. Such black holes containing our universe could result in an infinite loop in which universes have black holes that host an interior universe which also has black holes, forming an infinite loop.