The Naked Scientists

The Naked Scientists Forum

Author Topic: Was there a previous universe?  (Read 7515 times)

Offline MikeS

  • Neilep Level Member
  • ******
  • Posts: 1044
  • The Devils Advocate
    • View Profile
Re: Was there a previous universe?
« Reply #25 on: 30/01/2012 09:32:09 »
Mike and others.  The energy available from gravitational collapse comes from simple maths by the integration of the energy gained by a particle as it approaches a gravitating point source from a very large distance under the inverse square law.  Most of this comes when it is getting close to the gravitating point.

This is a good ref that shows the maths

http://hyperphysics.phy-astr.gsu.edu/hbase/gpot.html

You must also remember that a spherical object collapsing under its own gravity can be treated as a gravitational point source at the sphere's centre (of gravity).  This applies to particles both inside and outside of the surface of the sphere with the mass defined by the mass within the sphere defined by the radius from the location of the centre of gravity.

It follows that any object that is collapsing under its own gravity towards a mathematical point (however small the initial object) can release an infinite quantity of energy. 

We only need enough to create a reasonably sized universe like ours!
Unless an object is massive enough it will not collapse under its own gravity.  So where you say "(however small the initial object)" can't be correct.  If we start off with an initial object (star) of say ten solar masses (a small object just big enough to collapse under its own gravity) it has a finite mass and energy equivalence.  To create a universe as big as ours from that quite obviously would entail the creation of energy which is impossible.  I am not a mathematician but I believe that if the maths say it is possible then I would query what is wrong with the maths.
 

Offline Soul Surfer

  • Neilep Level Member
  • ******
  • Posts: 3345
  • keep banging the rocks together
    • View Profile
    • ian kimber's web workspace
Re: Was there a previous universe?
« Reply #26 on: 31/01/2012 00:04:36 »
No there is nothing wrong with it and it is perfectly reasonable and logical remember to make a ten solar mass black hole you have to squash your ten solar masses down to about ten miles across, and heading for the Planck length of 10^-35 metres is a hell of a lot of orders of magnitude smaller and even that is vastly bigger than a mathematical singularity  there is loads of energy available and it is not in any way breaking the physical laws.  It is just that people do not really bother to appreciate the real numbers involved in lots of these things.
 

Offline syhprum

  • Neilep Level Member
  • ******
  • Posts: 3821
  • Thanked: 19 times
    • View Profile
Re: Was there a previous universe?
« Reply #27 on: 31/01/2012 01:23:37 »
If as you say and the mathematics would seem to imply the gravitational collapse to a singularity leads to the generation of an infinite amount of energy this would seem to be an argument that a singularity cannot exist in a black hole.
There must be a balance where the the size of the collapsed body behind the event horizon is such that the energy liberated by the gravitational collapse is equal to the energy inherent in the original pre collapsed body.
 

Offline MikeS

  • Neilep Level Member
  • ******
  • Posts: 1044
  • The Devils Advocate
    • View Profile
Re: Was there a previous universe?
« Reply #28 on: 31/01/2012 08:41:30 »
syphum
That sounds logical.
 

Offline Soul Surfer

  • Neilep Level Member
  • ******
  • Posts: 3345
  • keep banging the rocks together
    • View Profile
    • ian kimber's web workspace
Re: Was there a previous universe?
« Reply #29 on: 31/01/2012 09:22:59 »
Yes, I think that there is and that is the limit of what happens in our universe but that does not prevent what I have described happening as well.  Let me explain.

The black hole would be perfectly normal in our universe if you pulled it into orbit around a star it would weigh exactly what you expected from the mass that went into it less any losses due to hawking radiation the point is that what is inside is decoupled from our universe now and is "somewhere else"

Think a bit about this at the instant of formation of the event horizon what is inside cannot get out. let us now say there is nothing outside to drop in to confuse the issue and what is inside continues to collapse towards this "singularity" to use the current fashionable expression.  This collapse may be quick but it will not be instantaneous.  At the moment the event horizon forms the escape velocity is equal to the velocity of light. so light can just reach the event horizon then fall back  Heavier things going at less than the velocity of light will fall back sooner. As the material collapses further this escape velocity get even higher and even light from what is in the middle will not even be able to reach the event horizon.  This is a sort of second "event horizon" let us call it the "light limit sphere".  Now this will continue to contract as the gravity increases.  Now between our event horizon and the light limit sphere if we looked inside the black hole we would see nothing except possibly hawking radiation. 

If you consider the "world lines" of things in the area between the event horizon and the light limit sphere they are becoming confined and unidirectional because all roads lead towards the singularity with gradually increasing strength so things are becoming essentially unidimensional and "stringy" whatever is in there is effectively decoupled form our universe.

I am a trained physicist and have been working seriously on this initial collapse of a black hole inside its event horizon for more than ten years and looking for others who are trying to do the same thing but so far failed to find any good references.  The nearest I can get is some papers about the actual initial formation of the horizon in dense collapsing material because if you look at it seriously it is quite problematic because it cannot form in the middle and work its way out because right at the centre of a normal gravitating object there is no field at all!  So it must form part way out where the field is very strong but where?  however the theorists do not look seriously at events happening inside the event horizon but within the range of our theoretical understanding during the time of collapse but jump immediately to the Scwartschild an Kerr solutions in the limit.  Thats a bit like saying that our universe is a big bang followed by a heat death with nothing interesting in between!
 

Offline syhprum

  • Neilep Level Member
  • ******
  • Posts: 3821
  • Thanked: 19 times
    • View Profile
Re: Was there a previous universe?
« Reply #30 on: 31/01/2012 09:40:19 »
Not being a trained physicist I can only take take a simplistic view, I believe that there is a fourth degree to which matter can be compressed the first stage is the density found within rocky planets up to about 20kg/m3 then that within white dwarfs, next that within neutron stars which is almost sufficient to produce an event horizon and lastly a quark soup where the density is sufficient to produce one.   
 

Offline imatfaal

  • Neilep Level Member
  • ******
  • Posts: 2787
  • rouge moderator
    • View Profile
Re: Was there a previous universe?
« Reply #31 on: 31/01/2012 10:02:49 »
Syhprum - I would go along with that to an extent, I am not sure that quark degenerate matter is the same as a black hole - ie that it has an event horizon.  . Edit - cannot find any firm data, but the explanations I have read place quark degenerate matter as position on a spectrum between neutron stars and black holes and thus definitely without an event horizon.  An event horizon for quark stars would basically be saying they were blackholes - and I can find nothing to suggest this

The wikipedia page on degenerate matter (and I have a selfish personal interest in ensuring that the degenerate do matter within society) is quite good - although the preon section is wildly theoretical

http://en.wikipedia.org/wiki/Degenerate_matter
« Last Edit: 31/01/2012 10:30:50 by imatfaal »
 

Offline syhprum

  • Neilep Level Member
  • ******
  • Posts: 3821
  • Thanked: 19 times
    • View Profile
Re: Was there a previous universe?
« Reply #32 on: 31/01/2012 14:44:32 »
Although the article quoted acknowleges the prorgressive stages of increasing density it still talks of singularities I am at a loss to understand why when the density becomes so high that an event horizon is created this transition from matter in a highly compressed form to one of  infinite density suddently occurs.

I am re-reading Soul Surfers views on this matter.
« Last Edit: 31/01/2012 14:50:05 by syhprum »
 

The Naked Scientists Forum

Re: Was there a previous universe?
« Reply #32 on: 31/01/2012 14:44:32 »

 

SMF 2.0.10 | SMF © 2015, Simple Machines
SMFAds for Free Forums