The Schwarzschild Radius is the size of a black hole with a certain mass. If you plug in the mass of our visible universe it gives a size larger than the visible universe. Ergo, we are inside of a black hole. There is also evidence that it was smaller in the past: it is expanding.

Black holes are formed by supernova explosions of supergiant stars with at least 6 solar masses. At the instant the event horizon formed there would be an enormous temporal gradient created between the inside and outside of the black hole. From the inside, it would appear as if the outside universe sped up, aged trillions of years. Most importantly the rate of infalling matter would increase to infinity, the entire universe being gobbled up in and instant. At the same instant the geometric Schwarzschild radius would expand to compliment the increase in the black hole's mass, to several billion lightyears. The observer would see a relativistic (apparent) expansion of the event horizon, moving outward like a shockwave at close to the speed of light, consuming everything in its path. The superdense quagma inside the black hole would expand as well, becoming less dense, maybe even sparse. As it travelled outward, the event horizon would begin to emit Hawking radiation in the form of gamma rays, but it would be so red-shifted that an observer would see microwaves, for example the cosmic microwave background might be an image of the inside of the spherical event horizon as it moves outward at close to the speed of light. Other forms of Hawking radiation might be virtual particles, emitted internally, giving rise to baryogenesis, clouds of hydrogen, and fundamental particles needed to form galaxies and stars. A process of renewal, triggered by a physical object, but carried out by a purely mathematical phenomenon having no physical existence itself except the ability to impose asymptotic force upon conventional matter and energy.

The new universe that results may have properties entirely dependent upon the triggering supernova: mass, isotopic makeup, shape, spin, vibration modes, etc.

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