Contracting universe

[Blueplanetbob]

When I think about an expanding and contracting universe I wonder if the eventual integration of black holes is the process of contraction. Its such a simple and obvious concept but yet not favoured by the scientific community, or in other words I cannot find very much written about it.
What have I missed that eliminates this line of thought?

[Nenad]

yes, the end of the universe is seen as a lot of black holes through out the universe. This is a result of Einsteins General Relativity. The reason this is not seen as viable is because of the current expansion of the universe. The universe is expanding and its expansion is accelerating instead of decelerating as should be the case with black holes and masses pull. The thought of dark matter and dark energy is only a theoretical concept that is yet to be proven.

[Blueplanetbob]

It is possible then that the universe is expanding because not enough time has elapsed for sufficient black holes to evolve?

[Phobos]

Welcome to Physics Forums, blueplanetbob!

The mass/energy of the universe was set from the beginning (Big Bang) and there is not enough (as far as we know) to pull everything back into a Big Crunch. Doesn't make much of a difference to the overall fate of the universe if the mass is in the form of stars or black holes or whatever.

Even black holes eventually evaporate.

[Blueplanetbob]

There must be a reason for black holes. If they are not the initial stages of collapsing the universe, what is their function? All the mechanics of the universe must occur within a logical and predictable concept. Surely that philosophy cannot be compromised to leave us with chaos? Surely they do not appear and disappear within an evolving universe for no reason?

[Phobos]

The Meaning of Life is unknown to science. Science just describes natural phenomena and explains the way they work. We can scientifically see that most black holes are end-stage remnants of giant stars and that black holes too will eventually evaporate away. Current evidences suggest that the universe is fated to fizzle out in the far, distant future (not 100% sure on that...still lots of ongoing research). What's the Meaning of it all? For now, that seems to be left to philosophy/religion.

[force5]

When I think about an expanding and contracting universe I wonder if the eventual integration of black holes is the process of contraction. Its such a simple and obvious concept but yet not favoured by the scientific community, or in other words I cannot find very much written about it.
What have I missed that eliminates this line of thought?

Although I'm not considered an expert, I like your line of reasoning. I believe that if or when we develop a much better understanding of both dark matter and dark energy, we could consider the following;

The universe consist of three kinds of stuff.(at the present time).
1) normal matter/energy
2) dark matter
3) dark energy

All of the normal matter/energy will decay leaving on DM and DE.
When there is no more regular stuff around and the universe can no longer expand, the dark energy will be attracted to the dark matter and initiate the contraction phase referred to as the big crunch.

[Blueplanetbob]

Although you are probably correct I am still loath to concede that black holes simply evaporate away.
Do you consider the following worthy of further thought?
If the final black hole contracted the universe to a singularity by the negative energy of gravity, then somewhere in that quantum vacuum there must be something on a parity with gravity that disappears and triggers the big bang and that as space-time re-emerges gravity is reintroduced?

[Prometheus]

All of the normal matter/energy will decay leaving on DM and DE.
I wonder why you think that normal matter and energy will decay leaving dark matter and energy, when the concepts of dark matter and energy are so poorly understood.

[force5]

I wonder why you think that normal matter and energy will decay leaving dark matter and energy, when the concepts of dark matter and energy are so poorly understood.

My model predicted DM and DE years before there consideration as a possibility. It also predicted Blackholes in the early universe which have been detected in recent months. Current theories indicate decay rates for all normal mater that we are aware of.

[Prometheus]

My model predicted DM and DE years before there consideration as a possibility.
OK. That sounds like a reasonable reason.

[force5]

OK. That sounds like a reasonable reason.

Hi Prometheus;

I'm not trying to avoid the Question but, intend to provide information to anyone that might be interested. I try to provide a response on the same level as the question. In other words, a general question produces a general response and with a specific question, I will try to provide a specific answer.

cheers.

[Nereid]

Although you are probably correct I am still loath to concede that black holes simply evaporate away.
Do you consider the following worthy of further thought?
If the final black hole contracted the universe to a singularity by the negative energy of gravity, then somewhere in that quantum vacuum there must be something on a parity with gravity that disappears and triggers the big bang and that as space-time re-emerges gravity is reintroduced?Something like this is in several different kinds of cosmological model - e.g. the 'oscillating universe'. However, as Phobos said earlier, the best data we have to date suggests that the universe will expand forever, expansion slowing but never stopping. But then, maybe an astronomical observation tomorrow might lead to a change in this view :wink:

[kurious]

There is also the possibility that if the universe oscillates by only a small amount then this would explain why dark energy today has a density similar to the density of atoms in the universe as a whole (dark energy density stays constant but normal matter decreases in density as the volume of space increases, so if the universe started out very small then the difference in densities would have been huge).However, this scenario would need to explain the abundance of the elements and the cosmic microwave background.