**Exploding Black Holes?**

Black hole theory has been around for a long time now and was first proposed by John Mitchell, a Fellow of the Royal Society, whose ideas were presented to the Society in 1783. Mitchell based his calculations on Newton's theory of gravity, the best available at the time.

So the theory has been around for over two centuries and is pretty well understood.

Just to make sure we are all on the same wavelength I have reproduced below a definition of black holes.

Hubble Space Telescope image of a black hole at the heart of a galaxy

**"Black hole : **A concentration of matter which has a gravitational
field strong enough to curve spacetime completely round upon itself so that
nothing can escape, not even light, is said to be a black hole. This can
happen either if a relatively modest amount of matter is squeezed to very
high densities (for example, if the Earth were to be squeezed down to about
the size of a pea), or if there is a very large concentration of relatively
low mass material (for example, a few million times the mass of our Sun
in a sphere as big across as our Solar System, equivalent to about the same
density as water).The escape velocity from the surface of the Sun is only
0.2 per cent of the speed of light, but if you imagine successive larger
objects with the same density as the Sun, the escape velocity increases
rapidly.One of the first people to analyse the implications of Einstein's
theory was Karl Schwarzschild. The general theory of relativity explains
the force of gravity as a result of the way spacetime is curved in the vicinity
of matter. Schwarzschild calculated the exact mathematical description of
the geometry of spacetime around a spherical mass, and sent his calculations
to Einstein, who presented them to the Prussian Academy of Sciences early
in 1916. The calculations showed that for any mass there is a critical radius,
now called the Schwarzschild radius, which corresponds to such an extreme
distortion of spacetime that, if the mass were to be squeezed inside the
critical radius, space would close around the object and pinch it off from
the rest of the Universe. It would, in effect, become a self-contained universe
in its own right, from which nothing (not even light) could escape. For
the Sun, the Schwarzschild radius is 2.9km; for the Earth, it is 0.88cm."

Okay. So far so good. So what's the problem?

Imagine a black hole that swallowed an entire galaxy, then another, and another, until the entire universe had been sucked into this enormous black hole. ( This is just a thought exercise, I know it can't happen so need to point it out to me). So now we have a black hole, containing all the matter of the universe, from which nothing can escape. Now you see the problem!

According to the Big Bang theory this is how the universe came into creation, from a singularity. But if nothing can escape from a black hole (singularity) how did the universe manage? It's supposed to be impossible. See The Big Bang Theory

What do I think?

I have no idea. On the one hand we are told nothing can escape from a black hole, on the other we are told it is how the universe came into existence. Perhaps I have got it all wrong and misunderstood something, either about black holes or the Big Bang. Is it that the singularity the Big Bang emerged from is somehow different to the singularity of a black hole? It's just that I am not aware of two types of singularity. Perhaps someone will be kind enough to explain it to me?

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