[lupacexi (OP)]

Do black holes explode?
   The big bang appears to be an explosion of a singular black hole where all the energy of the universe existed at a single point or alternatively most of the energy of the universe existed at a single point while additional energy was flowing into that point. The big bang explosion could have sent parts of the black hole all over the universe so that billions of mini-black holes were distributed in a sphere. Thus billions of black holes could have then exploded to produce the universe that we now see.  Alternately the distributed sphere of energy could still have had a black hole at the center which in turn exploded again to create a void of energy at the center and a sphere of energy that formed the universe. There are many possibilities.
   The latest report from the astronomers is that our galaxy black hole exploded 6 million years ago producing very high temperature energy which left the center of our galaxy empty of stars. The indications are that a black hole eats up matter and at a certain point spits it out. One possibility is that black holes continually eat matter and continually spit out energy. The alternative is that it builds up energy and then blows up. Another possibility is that it does both. It continually radiates energy but eats more than it throws up and then over time reaches a point where it explodes.
  We have a lot of possibilities. What do you guys think from existing theory?

[evan_au]

It seems that there is a lot of speculation here about the Big Bang, Black Holes, and Black Hole "Evaporation".

To see what current theories say about these topics, I suggest you start here:

Do black holes explode?

Theory suggests that microscopic black holes can explode into our universe, at the end of their lives, see:
https://en.wikipedia.org/wiki/Micro_black_hole#Hawking_radiation

Large black holes don't explode into our universe. However, our usual concepts of time & space get scrambled inside a black hole, so nobody is quite sure what happens at the central singularity - some theoreticians have suggested that perhaps it can explode inside a black hole?
https://en.wikipedia.org/wiki/Multiverse#Black-hole_cosmology

our galaxy black hole exploded 6 million years ago producing very high temperature energy which left the center of our galaxy empty of stars

The black hole in the center of our galaxy is estimated to mass a few million times more than the Sun. This is not a microscopic black hole! So, as far as we know, the black hole itself will not explode.

There are some things that can cause explosions near a black hole:
- A large cloud of gas and stars will be torn apart before falling into the black hole. This produces a large outburst of energy from the accretion disk just outside the black hole.
- Our galaxy sometimes swallows other galaxies. When the core of the other galaxy (usually including another black hole) is swallowed by our galaxy, the merger of the black holes will produce an ever larger outburst of energy from the accretion disk just outside the black hole. In addition, the orbiting central black holes will clear out a region of space in the center, by swallowing the stars there, or by flinging them far away.

See: https://en.wikipedia.org/wiki/Black_hole#Accretion_of_matter

[Bill S]

https://www.spaceanswers.com/deep-space/how-do-intergalactic-and-extragalactic-space-differ-from-each-other/

Could the Big Bang have been a black hole?
The Big Bang is said to represent a space-time singularity – the point in a black hole where space-time curvature is at a maximum and a point where no solid object can survive – but it didn’t originate from a black hole.
Instead, when you think about it – the Big Bang has more of a resemblance to the reverse of a black hole, called a white hole, since everything that we see today originated from that small point rather than being pulled into it. However, the Big Bang isn’t a white hole either.
What we do know, though, is that black holes are responsible for phenomena such as quasars rather than the Big Bang – so we shouldn’t expect any miniature Big Bangs occurring in the universe.

[yor_on]

There is no 'single point' of a Big Bang. At least I never seen anyone prove that concept, so let's start there.
Can you prove it?
=

John Rennie seems to have drawn similar conclusions to me.
Now, that's more like it :)

https://physics.stackexchange.com/questions/136860/did-the-big-bang-happen-at-a-point

[Bill S]

https://physics.stackexchange.com/questions/136860/did-the-big-bang-happen-at-a-point

The simple answer is that no, the Big Bang did not happen at a point. Instead it happened everywhere in the universe at the same time.

It didn't happen at a point within the Universe; but could the Universe be defined as "a point" at the initial instant?

[yor_on]

I don't see how Bill. Like some 'unfolding origami knot'? Or as a 'hologram'? The one with Einsteins five dimensions? The universe is isotropic and homogeneous at large scales, and should be the same wherever you are  in time and space. Whatever it takes it will have to accept the same stars we see, there has to be an order, and considering the universe to be infinite, that's a lot of stars to keep count on, all (oldest light) then produced 'simultaneously' as that is what you will see at the observable edge of wherever you are. Wherever you are the early light will come in-reaching too, and its 'age' will be the same.

But yes, why not?

[evan_au]

The universe ... should be the same wherever you are  in time...

I don't think "isotropic and homogeneous" applies to time:
- The average density of the universe has changed over time
- The temperature of the CMBR has changed over time
- The mixture of elements has changed over time

[syhprum]

Why are all these semi magical properties attributed to blackholes ? ,to my mind a BH is similar to a Neutron star where the original matter has been subjected to one further stage of compression resulting in an escape velocity greater than c.
Little is known about this more highly compressed form but are there any theoretical reasons why it should not exist

[Bill S]

….could the Universe be defined as "a point" at the initial instant?

I don't see how Bill. ……The universe is isotropic and homogeneous at large scales, and should be the same wherever you are  in time and space.

If we think of the Universe as having “come into being” as a “primeval atom”, a “single quantum” or whatever; are we talking about “large scales”? 

Would being "a point" prevent it from being “isotropic and homogeneous”?

Whatever it takes it will have to accept the same stars we see….

I thought there were no stars around at the BB.

[Bill S]

Why are all these semi magical properties attributed to blackholes ? ,to my mind a BH is similar to a Neutron star where the original matter has been subjected to one further stage of compression resulting in an escape velocity greater than c.

I'll not argue with that.  We do seem to have drifted from BHs to BB, as so often happens.  I suspect they may not be analogous; but suspicions are there to be falsified.

[yor_on]

" I don't think "isotropic and homogeneous" applies to time: "

That one you need to explain Evan, would you mean that it only has one arrow? That's true, but under that arrow, has the universe changed from a isotropic homogeneous appearance? And if you read the 'stipulations' defining it, which then would be the thoughts of John Rennie and the way I look at it too, there is no 'single point of entry' for a 'Big Bang'. Which means, extrapolating, that each point becomes 'equal' in its evolution, as I think of it.

[yor_on]

In a perfect theoretical description Bill the 'scale' shouldn't matter for this. If we find it homogeneous and isotropic at one scale, it should hold all the way down :) Turtles all the way.Then again, it's my view.

[evan_au]

" I don't think "isotropic and homogeneous" applies to time: "
That one you need to explain Evan

If you compare two large volumes of space (larger than 1 billion Light Years across), they will be statistically similar.
- That is what isotropic and homogeneous means

If you compare the equivalent volume of space at two different times (more than 1 billion years apart), they will be statistically different in their composition and density.
- That is not isotropic or homogenous

I think what you are saying is that if you compare two large volumes of space, they will be statistically similar no matter how long it is since the Big Bang (ie provided they are similar ages).
- I agree that this is a reasonable interpretation of isotropic and homogenous
- But in a relativistic environment, the interpretation of the "same" time is a bit problematic.

[yor_on]

And what exactly did you think I meant by something ideally being isotropic and homogeneous in my answer to Bill? Comparing this time to a million years ago, or looking out at the universe at two different times, both times finding it to look much the same no matter in what direction you look?

Take a guess
=

Think I answered that question thinking of something else Evan, Bill took up the question if it would be different scaling it back into a point. and I think myself that this shouldn't really matter for what we see, actually made me think of fractals too that question. But all of it 'ideally'. So maybe I shouldn't get all 'eh ***' :) Seems we thought in two different approaches. I didn't even consider 'time' for that one, just thought about it in form of scaling something down.

[Bill S]

I guess the answer to my question at #8 (Would being "a point" prevent it from being “isotropic and homogeneous"?) would be "no"; which is what I suspected.