Beyond the big bang

[Robert Tulip]

Is the following description scientifically possible?

The singularity existed before the big bang for trillions of years, having coalesced from rivers of black holes drawing together a previous expansion. Our phase of time is due to turn around by gravity many billions of years hence, with each galaxy falling into the black hole at its centre and streaming rivers of black holes then rushing back together with gathering speed to form a new singularity.

[ravens_cry]

Well. . .as attractive an idea as that sounds, I don't think it sounds plausible from what I know about what we know about the nature of the universe. It looks as if from where we stand now, the universe is not only expanding forever, but also accelerating. Which means there just isn't enough mass in the universe to collapse it down into that 'big crunch' state.
That is how I understand it anyway.
Please correct me if I am wrong here people.

[RussT]

Is the following description scientifically possible?

The singularity existed before the big bang for trillions of years, having coalesced from rivers of black holes drawing together a previous expansion. Our phase of time is due to turn around by gravity many billions of years hence, with each galaxy falling into the black hole at its centre and streaming rivers of black holes then rushing back together with gathering speed to form a new singularity.

Not quite, BUT if this were not in Q&A, I could show how to change a couple of things to have a viable non-BB working "Open System" Universe...;) Which Is what you are suggesting.

And, that would come with 'mainstream' SMBH's...at least the nothing escaping 'up' from the event horizons, and would also come with mainstreams non-baryonic DM (Not WIMPS) needed for galaxy rotation curves...;)

[mugaliens]

It's somewhat poetic, though...

[Robert Tulip]

Well. . .as attractive an idea as that sounds, I don't think it sounds plausible from what I know about what we know about the nature of the universe. It looks as if from where we stand now, the universe is not only expanding forever, but also accelerating. Which means there just isn't enough mass in the universe to collapse it down into that 'big crunch' state.
That is how I understand it anyway.
Please correct me if I am wrong here people.

It's somewhat poetic, though...
Thanks. I find it really hard to intuitively grasp that the universe could be expanding forever. A pulsating sequence of big bangs looks neater than a one-off pop.

What is the possible force driving acceleration, given that gravity is a real countervailing force?

I would be interested in references to how strong the evidence is for an accelerating expansion.

[Cougar]

I would be interested in references to how strong the evidence is for an accelerating expansion.

Well, for the past 10 years scientists around the world have been seeking a flaw in the logic or an error in the measurement. There have been speculations about "gray dust" or a large bubble of underdense mass that we may happen to be in, but I haven't heard of any deal-breakers.


A pulsating sequence of big bangs looks neater than a one-off pop.
The Universe can't hear you. :)

[Robert Tulip]

Well, for the past 10 years scientists around the world have been seeking a flaw in the logic or an error in the measurement. There have been speculations about "gray dust" or a large bubble of underdense mass that we may happen to be in, but I haven't heard of any deal-breakers. The Universe can't hear you. :)Thank you. So until astronomers find more mass it seems the universe is on a one way ticket to dispersion. Recognising that evidence trumps imagined elegance, I simply find it more conceptually elegant to speculate that matter would persist beyond the period of our big bang expansion, and that this would require the universe to eventually shrink back to a point under force of gravity.

Three further questions if I may:

1. How big is the gap between the outward momentum of the universe and the force of gravity to turn it around?

2. Do we know that the big bang singularity had no physical size?

3. Could the big bang have concealed from our view a large black hole containing all the matter of the universe?

[Hornblower]

Thank you. So until astronomers find more mass it seems the universe is on a one way ticket to dispersion. Recognising that evidence trumps imagined elegance, I simply find it more conceptually elegant to speculate that matter would persist beyond the period of our big bang expansion, and that this would require the universe to eventually shrink back to a point under force of gravity.Elegance is in the eye of the beholder.

What's wrong in principle with the possibility that matter persists but continues to disperse? What does that have to do with elegance?

[Robert Tulip]

Elegance is in the eye of the beholder.

What's wrong in principle with the possibility that matter persists but continues to disperse? What does that have to do with elegance?Elegance might be the wrong word here, it is just easier for me to imagine that ours is one of a sequence of universes than that all matter came into existence at one moment preceded by nothing. The great dispersal of the universe seems a rather bleak prospect, with each galaxy collapsing into a black hole at its centre, and then moving further away from everything else for ever. The reason I imagine it would eventually turn around is that the only external force is gravity of the whole, so momentum is always declining. Thinking in terms of trillions of years, I just can't imagine that the force of gravity can never match the force of outward momentum. Perpetual expansion is like saying that the original bonds of the big bang universe have snapped.

So posing the same question three ways
1. Is the speed at which galaxies disperse likely ever to decline due to gravitational attraction of other galaxies?
2. With no force against gravity except momentum, would the universe eventually reach a situation where the total gravity acting on its far flung members equalled the total outward momentum?
3. Does the speed of dispersal exceed the escape velocity of the mass of the universe?

[cosmocrazy]

Is the following description scientifically possible?

The singularity existed before the big bang for trillions of years, having coalesced from rivers of black holes drawing together a previous expansion. Our phase of time is due to turn around by gravity many billions of years hence, with each galaxy falling into the black hole at its centre and streaming rivers of black holes then rushing back together with gathering speed to form a new singularity.

It seems that the universe is accelerating apart, so this theory at the moment seems doubtful, But!

What if that's exactly what's happening right now?

The universe could be so vast that from our perspective it seems to be expanding but in fact it is the galaxies that are accelerating toward the centre of mass with the nearest ones accelerating faster? If you consider the universe to be an unbound closed system then perhaps this is the perspective we would encounter in this situation?

[formulaterp]

it is just easier for me to imagine that ours is one of a sequence of universes than that all matter came into existence at one moment preceded by nothing.

But didn't the sequence have to start somewhere? What preceded that?



Thinking in terms of trillions of years, I just can't imagine that the force of gravity can never match the force of outward momentum. Perpetual expansion is like saying that the original bonds of the big bang universe have snapped.

Imagine a universe with just 1 planet, and 1 rocket. You launch the rocket and exceed escape velocity. You can wait all the trillion years you want. It ain't ever coming back.

[cosmocrazy]

But didn't the sequence have to start somewhere? What preceded that?.

True!





Imagine a universe with just 1 planet, and 1 rocket. You launch the rocket and exceed escape velocity. You can wait all the trillion years you want. It ain't ever coming back.

Not necessarily, if they exist in a closed loop universe it would eventually go full circle without changing course.

[mugaliens]

What is the possible force driving acceleration, given that gravity is a real countervailing force.

This is a misnomer, as it appears you're ascribing acceleration to the distance between objects in the universe, implying relative movement.

That's not expansion.

Expansion is the increase in the size of spacetime itself. It is not brought about by objects moving away from one another. Rather, the expansion of spacetime carries objects away from one another. Think of it as dots on a balloon, that are free to slide around on the surface in respect to gravitational attraction. If the balloon is static, they're moving towards one another. But if you inflate the balloon, it expands, and the distance between the dots increases, at least for dots which are relatively distant. Dots that are bunched up close to one another move towards one another faster than the underlying spacetime, er, balloon surface, can expand.

It's the rate of expansion of spacetime which is increasing, thus, it's expansion of spacetime itself which is accelerating, not the objects' relative velocities due to some "force." Furthermore, gravity predominates, "locally," and by that, I mean anything galactic or smaller. Even in galactic clusters gravity predominates over expansion.

But in the vast reaches of empty space between galactic clusters, the effects of expansion overcome the effects of gravity.

Another note on expansion: It appears to be uniform throughout the universe. That is, it's not affected by local variations in mass or the gravitational warping of spactime by that mass. It's just that locally, the effects of gravity cause the dots on that balloon to slide along its surface faster than the balloon can expand.

[speedfreek]

It's somewhat poetic, though...

As was your last post. A most excellent explanation of expansion.

[Ken G]

I think the key issue with questions like in the OP is, you have to decide if you will engage in science, or in speculation. If the latter, there are no wrong answers as long as you don't directly contradict an observed fact. That's actually pretty easy to avoid, so you can use pretty much any rules you like, including "the way that makes sense to me". However, if you will engage in science, the requirements are very different-- you have to winnow down the speculative possibilities based on whichever ones actually conform to some kind of observational evidence. When you do the latter, you find that there is only observational evidence of an accelerating expansion that will not return.

Of course, observational evidence is always incomplete, and so one always has room to speculate. Science does not trump speculation-- but it is also not the same thing as speculation.

[cosmocrazy]

As was your last post. A most excellent explanation of expansion.

Agreed!

Along with Ken's point about science and speculation! :)

[Robert Tulip]

This is a misnomer, as it appears you're ascribing acceleration to the distance between objects in the universe, implying relative movement. That's not expansion. Expansion is the increase in the size of spacetime itself. It is not brought about by objects moving away from one another. Rather, the expansion of spacetime carries objects away from one another. Think of it as dots on a balloon, that are free to slide around on the surface in respect to gravitational attraction. If the balloon is static, they're moving towards one another. But if you inflate the balloon, it expands, and the distance between the dots increases, at least for dots which are relatively distant. Dots that are bunched up close to one another move towards one another faster than the underlying spacetime, er, balloon surface, can expand. It's the rate of expansion of spacetime which is increasing, thus, it's expansion of spacetime itself which is accelerating, not the objects' relative velocities due to some "force." Furthermore, gravity predominates, "locally," and by that, I mean anything galactic or smaller. Even in galactic clusters gravity predominates over expansion. But in the vast reaches of empty space between galactic clusters, the effects of expansion overcome the effects of gravity. Another note on expansion: It appears to be uniform throughout the universe. That is, it's not affected by local variations in mass or the gravitational warping of spactime by that mass. It's just that locally, the effects of gravity cause the dots on that balloon to slide along its surface faster than the balloon can expand.

Thank you. So, we have God blowing up a balloon, with galaxies on its surface, as an analogy for the expansion of the universe. If God is blowing at a steady rate, the galaxies will separate faster while the balloon is small, but once it gets big, say in a trillion years, the rate of separation will be slow, and the small gravitational attraction between galactic groups can come into play. What is then to stop the whole shebang from collapsing on itself?

[Jeff Root]

So posing the same question three ways
1. Is the speed at which galaxies disperse likely ever to decline due to
gravitational attraction of other galaxies?
Before the acceleration of the expansion was discovered in 1998, that
is what was assumed was happening. Observations of supernovae at
cosmolgical distances show that it is in fact doing the opposite, and
that for some reason, galaxy clusters are moving away from one another
faster and faster as time goes by.

I have an ATM speculation which predicts that the acceleration should
have been large in the early Universe and decrease asymptotically
toward zero as the galaxy clusters get farther apart. That would mean
that the speed of separation continues to increase forever, but at an
ever-decreasing rate. The mainstream view, however, is that the
acceleration is either constant or increasing, not decreasing.



2. With no force against gravity except momentum, would the universe
eventually reach a situation where the total gravity acting on its far
flung members equalled the total outward momentum?
Before the discovery of the acceleration, the big question was whether
the Universe has a great enough density to be "closed" or not. Even
with dark matter (whatever it is), the density appeared to be far too
low to eventually stop the expansion and start bringing far-flung galaxy
clusters back together.



3. Does the speed of dispersal exceed the escape velocity of the mass
of the universe?
In effect, yes. You could find info about this by searching for terms
"cosmological constant" and "density parameter".

-- Jeff, in Minneapolis

[Ken G]

If God is blowing at a steady rate, the galaxies will separate faster while the balloon is small, but once it gets big, say in a trillion years, the rate of separation will be slow, and the small gravitational attraction between galactic groups can come into play. What is then to stop the whole shebang from collapsing on itself?Don't take the analogy too literally-- we don't actually need anything "blowing" into the balloon. The objects on the balloon are massive, and they are moving fast, so they are very hard to turn around. Indeed, their inertia seems to be enough by itself, by about a factor of 3, to prevent the balloon from ever contracting back on itself. For good measure, "God" appears to be blowing into the balloon (the cosmological constant), only he is blowing faster, not slower, as the balloon expands. We appear to already be at a place where the net gravity is repulsive, not attractive, on the largest scales.

[astromark]

Some of the most intelligent replay's I have ever seen... I hope I do not spoil the trend.
Observable and verified by cosmologists is the fact. The universe is continuing to accelerate its rate of expansion. That does seem to preclude any future reversal.
I spend some time with physics educators and while hosting public viewing we often get some pretty good conversations at the Ward Observatory. One of these conversations recently became an excellent platform for three of these math head over educated buffoons wanted to out do each other. Its as if they were attempting to out do each other with science. The explanations for the accelerated rate of this universes expansion and the how and why parts of it were riviting...
The pity of it is that my appalling ability to recall with accuracy any part of this is just a we bit annoying... but It was a very compelling argument.... :)Not a balloon in sight... LOL.mark.

[Cougar]

...it is just easier for me to imagine that ours is one of a sequence of universes than that all matter came into existence at one moment preceded by nothing.

We don't know that "all matter came into existence at one moment preceded by nothing," and although popular descriptions might put it like that, especially older ones, this is not really part of the big bang theory, which describes the evolution of the universe after that initial expansion. We know there must have been a very early time when everything was extremely hot and dense but expanding and cooling, otherwise we would not have the observed abundances of hydrogen and helium. What was going on to cause such a state, or if there was anything "before," we do not know.

You speak of the singularity as if it is a well-defined thing. It is not. It simply marks the end of our current understanding.

[John Mendenhall]

Not necessarily, if they exist in a closed loop universe it would eventually go full circle without changing course.



Sorry, no evidence to support this. Universe is flat to 2 to 3 percent as far as we can tell, and the upper limit is probably lower than this.

[cosmocrazy]

Sorry, no evidence to support this. Universe is flat to 2 to 3 percent as far as we can tell, and the upper limit is probably lower than this.

My bold.
At present strong evidence supports a flat universe i fully agree, but its not conclusive. I was just pointing out that there are possibilities that may result in the rocket going full circle. ;)