What Is Beyond The Observable Universe?

[sylas]

That mean we can study all history of a black hole after its born just observing more and more redshifted signals? Very interesting.

I qualified my remarks to say IF we could actually see a signal redshifted arbitrarily far. But we can't.

If you think in terms of a classical wave, a red shifted signal is one in which the distance between successive wave crests becomes large. That is, wavelength increases as light is shifted into the infrared.

Light is also quantized... it is made up of photons. Another difference with a red shifted signal is that the distance between successive photons is increased... or in other words, you get less photons per unit time. As a signal is shifted arbitrarily far, in the limit there is an arbitrary distance between photons.

Another way of think about it. A particle crossing an event horizon emits only a finite number of photons before it has crossed the horizon. Hence there are only a finite number of photons available to an observer. There will be a last photon from an arbitrarily redshifted source, after which... nothing more, ever.

Why we don't observe that kind of "frozen" galaxies right now? I think right now must be a lot of galaxies beyond the current event horizon already. Or I'm wrong?

Well, yes, there are galaxies "now" beyond the event horizon, assuming a universe homogenous on large scales and a ΛCDM model. But have a look at the diagram from Davis and Lineweaver, attached above in message [post=2591939]post #135[/post]. and read off the implications.

We can only ever see matter before it crosses the event horizon. In the current epoch, the oldest light we see is the cosmic background radiation. The galaxies formed from that material, given a (0.3,0.7) ΛCDM model, crossed the event horizon long ago. But what we see now is still only material from which they were made, redshifted with about about z=1088. Time is not quite frozen, but in the signal we perceive it appears to run about 1089 times more slowly than reality. We don't even see it formed into galaxies yet.

Given enormous lengths of time and the capacity to see extreme redshift signal, it will eventually be possible to see it formed into galaxies. That material will have crossed our event horizon (from the diagram) about a billion years after the Big Bang; which is comparable to the age of the most distant actual galaxies we can now see.

What about galaxies we see with z=9? That's a little bit more redshifted that the best we've observed so far, but its close. We would be seeing light emitted when the scale factor was a=0.1, and there's a vertical line in the diagrams to help pinpoint those galaxies. So this is a convenient example.

The z=9 galaxy will have crossed the event horizon about 4 billion years after the Big Bang; and what we see now is from less than a billion years after the Big Bang. So in principle, there are still three billion more years of their history potentially visible to future astronomers.

Now... hold on to your hat and think on this. Consider material from a=0.001 (which is very close to what we see in the CMBR) and material from a=0.1 (which is very close to the most distant galaxies detected). When in the future would we be potentially able to observe that CMBR material developed into galaxies at the same epoch as we now observe in the most distant galaxies? You can read that off the diagram; it will be hundreds of billions of years into the future.

I have not done the actual calculations for myself. Sometime I might try it, for fun.

Cheers -- sylas

 

[Calimero]

And YOU MUST UNDERSTAND WHY the Hubble parameter at any time t is equal to a certain fraction H(t) = a'(t)/a(t).
This is a sort of non-trivial interesting fact, nice to think about. The time derivative of a(t) divided by a(t) itself. The Hubble parameter H(t) is the time derivative of the scalefactor divided by the scalefactor itself, at any given instant in time.

I have two questions:

1. Is there any significance in fact that when we divide speed of light wit current H(t) we get 13.6 GLY?

2. How can we see something that is now and ever was (at least when light ventured towards us) receding from us faster then light?

 

[sylas]

1. Is there any significance in fact that when we divide speed of light wit current H(t) we get 13.6 GLY?

No. Current indications are that it is simply a co-incidence.

2. How can we see something that is now and ever was (at least when light ventured towards us) receding from us faster then light?

Because as the photon crosses space, it eventually moves into regions where co-moving observers are receding at less than the speed of light. The "proper distance" from us to a photon emitted from such a galaxy makes a kind of pear shape. Initially, when the photon is emitted, the proper distance from us to the photon is actually increasing. That is, the direction of motion of the photon is towards us, but the distance between us and the photon is increasing, at first, because of how the universe expands.

You can reasonably speak of a "recession velocity" for the approaching photon. Locally, the photon moves at c. But the rate of change of proper distance from us to the photon is another matter. Initially, it is receding; but as it crosses space it recedes more and more slowly. Eventually, it moves into a region where the co-moving recession velocity is equal to the speed of light. At that point, the "recession velocity" of the photon is zero. But the recession velocity continues to fall, so that the photon from this point actually starts to become closer to us.

Eventually, the photon comes into our own local region of space, and it is now approaching at the speed of light.

Cheers -- sylas

 

[marcus]

...2. How can we see something that is now and ever was (at least when light ventured towards us) receding from us faster then light?

Because as the photon crosses space, it eventually moves into regions where co-moving observers are receding at less than the speed of light. The "proper distance" from us to a photon emitted from such a galaxy makes a kind of pear shape. Initially, when the photon is emitted, the proper distance from us to the photon is actually increasing. That is, the direction of motion of the photon is towards us, but the distance between us and the photon is increasing, at first, because of how the universe expands.

You can reasonably speak of a "recession velocity" for the approaching photon. Locally, the photon moves at c. But the rate of change of proper distance from us to the photon is another matter. Initially, it is receding; but as it crosses space it recedes more and more slowly. Eventually, it moves into a region where the co-moving recession velocity is equal to the speed of light. At that point, the "recession velocity" of the photon is zero. But the recession velocity continues to fall, so that the photon from this point actually starts to become closer to us.

Eventually, the photon comes into our own local region of space, and it is now approaching at the speed of light.

Calimero, I agree with everything Sylas said here. He gave you a good answer. But left out an important reason why this happens. It has to do with H(t) decreasing.
In the past it has decreased very rapidly. H(t) used to be like 1.3 million (when the background was emitted) and is now only 71. A huge decrease. Playing with the calculator let's you track this decrease.

You showed that you know how to get the HUBBLE RADIUS c/H. Good, so when H was decreasing rapidly then c/H was increasing rapidly.

But notice this distance divides space into two regions: Anything outside that radius is receding faster than c and anything inside is receding slower than c.

So if a photon is aimed at us, it may at first be swept back by expansion of distance as long as it is outside the c/H radius. But if it hangs in there and keeps trying to reach us, then eventually it may happen that c/H reaches out and takes it in.

Once it is inside the region of slower than c recession then its own speed dominates and it will gradually reduce its distance to us. It will gradually get closer.

The key thing is that in the past the c/H radius has extended out very very fast.

This is the basic reason we can see a lot of stuff which, when it originally emitted the light, was receding several times faster than c.

You can see this happening graphically in an animation. Google "wright balloon model"

The wiggly things (cartoon photons) travel a fixed speed like 1 millimeter per second. The whirly things are galaxies

 

[Calimero]

Marcus and Sylas, thank you both.
So what is now receding at, say, 2 C will need much more time to reach to us (light from it) then it would need earlier in the history?
And what is 'proper distance' ? Distance measured if we freeze expansion, and then measure? Also, what is proper time?

 

[sylas]

And what is 'proper distance' ? Distance measured if we freeze expansion, and then measure? Also, what is proper time?

Proper time is simply time as measured by a conventional clock that is at rest with the Hubble flow. That is, there's no additional peculiar motions to worry about. You can also think of it as the time measured by co-moving clocks.

Your description of proper distance is fine. Another way to think of it... imagine all of space filled with co-moving observers equipped with conventional clocks and rulers. The proper distance between two co-moving observers at a designated proper time instant would be the instantaneous sum of distances given by all the co-moving rulers.

And thanks Marcus for adding the point about H changing over time!

 

[marcus]

So what is now receding at, say, 2 C will need much more time to reach to us (light from it) then it would need earlier in the history?
...

Indeed infinitely more, will never get there. Good intuition. Abs. on target!

In fact even 25% greater than c and the galaxy cannot send us a message that will reach us.
This is because H(t) is decreasing so much slower now than in the past. So the distance c/H is reaching out so much more slowly now.

The distance limit as of now is about 15 Gly. Somewhere between 15 and 16 as I recall.

If a galaxy is within that range, we could send a light signal to it today that would reach it eventually. And some event occurred there today, an explosion say, we would eventually see it. Even though the distance to the galaxy is increasing faster than c.

But if it is beyond that range today, say more than 16 Gly in "now" freezeframe distance, we can as of today send no signal that will get there. But of course there is plenty of information already on its way, we can look forward to watching her for a long long time. Just nothing she does from now on will ever reach us.

As a very very rough estimate (Sylas may be able to refine this) the breakpoint is redshift z = 1.6
You can refer to Morgan's cosmos calculator and see what that corresponds to in distance terms. It corresponds to distance just slightly less than 15 Gly, and a recession rate of around 1.1 c.

I haven't checked this but I think its roughly right.

It used to be that H was decreasing so fast that material could be receding at 3 c or faster and emit light and it would reach us. Now if a galaxy or other material is receding at even 1.15 c or so, it can't reach us
but if it is receding 1.05 c it can emit light that will still eventually reach us.
And borderline is around 1.1.

I'm overstating the precision because I want to talk concrete examples, but I don't actually know the breakpoint (and it depends on cosmo parameters like 0.73 and 0.27 and 71 which are themselves uncertain!)

I have to go do something realworld. Can't finish this post. Sylas mentioned something extremely interesting--observers at rest with respect to the expansion process itself.

In practical terms that means at rest with respect to the ancient light. the background. that means no doppler hotspot in any direction, when you measure the microwave sky temperature. Absolutely an all important concept.
The concept of a network of observers at rest is what the ideas of NOW and then rest on, the idea of being able to specify a moment when you freeze expansion in order to define the freeze distance. The time "t" that is really there in the Hubble law v = H t. That time depends on the concept of being at rest with respect to background, or with respect to the expansion process. It is so important, so basic. It is the "t" in the basic Friedman equations model that all cosmology rests on, and the "t" of the scalefactor a(t).

Have to go move the car, however, because tomorrow is street cleaning. Don't want to get a ticket.

 

[E=mc^84]

We may not be able to observe it at the moment but we need to make the assumption something is there. We have never seen life outside our planet but we assume it exists and create ways to seek out and prove it. A similar thing should be done in cosmology. We should be making insturments that can help us study the beyond.



Yes it maybe irrevelent and these other universes may contian different laws of Nature. However like alien life, I do think we will be able to learn about it in the future. We shouldn't give up. No one has ever seen a quark (correct me if I'm wrong) but we assume the microverse goes further.

If we had a spaceship that can do this, what do you think it will run into at the ends of the universe? Will the spaceship keep going or is it constricted to this universe only? What do you think?

What if we can observe it indirectly lke we do with black holes?

 

[Calimero]

In fact even 25% greater than c and the galaxy cannot send us a message that will reach us.
This is because H(t) is decreasing so much slower now than in the past. So the distance c/H is reaching out so much more slowly now.

The distance limit as of now is about 15 Gly. Somewhere between 15 and 16 as I recall.

If a galaxy is within that range, we could send a light signal to it today that would reach it eventually. And some event occurred there today, an explosion say, we would eventually see it. Even though the distance to the galaxy is increasing faster than c.

But if it is beyond that range today, say more than 16 Gly in "now" freezeframe distance, we can as of today send no signal that will get there. But of course there is plenty of information already on its way, we can look forward to watching her for a long long time. Just nothing she does from now on will ever reach us.

As a very very rough estimate (Sylas may be able to refine this) the breakpoint is redshift z = 1.6
You can refer to Morgan's cosmos calculator and see what that corresponds to in distance terms. It corresponds to distance just slightly less than 15 Gly, and a recession rate of around 1.1 c.

I haven't checked this but I think its roughly right.

It used to be that H was decreasing so fast that material could be receding at 3 c or faster and emit light and it would reach us. Now if a galaxy or other material is receding at even 1.15 c or so, it can't reach us
but if it is receding 1.05 c it can emit light that will still eventually reach us.
And borderline is around 1.1.

I'm overstating the precision because I want to talk concrete examples, but I don't actually know the breakpoint (and it depends on cosmo parameters like 0.73 and 0.27 and 71 which are themselves uncertain!)

That numbers are just about right according to calculator. Does it mean that it tends to even at C at some distant future?

Let me ask you another question about calculator. I obviously lack math behind it, but for any redshift (z), you can put any value for H(t) above ~35 and speed away is not affected, just the distance is changing proportionally. Why is that? Can you even "go trough time" with changing just H(t), or you must change Omega too?

 

[Chronos]

So how are we able to observe the CMB at z ~ 1090? I perceive an ATM reply.

 

[sylas]

So how are we able to observe the CMB at z ~ 1090? I perceive an ATM reply.

What is the problem? At that redshift, the wavelength is in the microwave region, at about 2mm wavelength. You observe it with a microwave receiver; nothing ATM about it.

 

[marcus]

That numbers are just about right according to calculator. Does it mean that it tends to even at C at some distant future?

Let me ask you another question about calculator. I obviously lack math behind it, but for any redshift (z), you can put any value for H(t) above ~35 and speed away is not affected, just the distance is changing proportionally. Why is that? Can you even "go trough time" with changing just H(t), or you must change Omega too?

Calimero I just this moment saw your post it is after midnight here and I need to get some sleep. Other wise I'd answer!
I found a source with exact estimates of the cosmic event horizon.
A paper by Egan and Lineweaver (excellent guy)
I was saying something like 15 Gly and in fact that was close---actually 15.7 Gly. But it is shifting slightly and in the longterm limit it will be 16.4 Gly
Yes. Asymptotically the recession speed will be c at that distance. Your intuition was correct.

I can't answer your question about the calculator right now because sleep is more important. In case anyone wants to look at Egan Lineweaver I'll get the link.
http://lanl.arxiv.org/abs/0909.3983
It is a technical paper but it has some useful numbers in an appendix at the end.

So on Lineweaver's excellent authority, if a galaxy is 15.6 Gly from us right now, then we could send them a message today and it would eventually get there! But it would take a hell of a long time.
And if the galaxy is now 15.8 Gly from us there is no way, the message would never get to them. Even if we set off a supernova they would never see it.

 

[lambdaorionis]

May I try and simplify...

Observable = Baryonic matter
Outside this is the Vaccum -

The Big bang did not cause the baryonic matter to "spread out" but it is the reaction of the vacuum which is responsible.
The big bang did not start from a singularity.

Anyone like to add?

 

[qwe]

Is it just black space extending forever? Or perhaps black space for a finite distance until another universe?

I find it hard to believe our universe is just the only universe. I don't see how it wouldn't extend for eternity instead. What is so special about our universe and the space we are in?

What do you think?

By logical necessity, there is literally 'nothing' beyond the observable universe. It is impossible to apply falsifiable predictions to something that is inherently unobservable.

In other words it is more in the realms of philosophy right now. But don't you think in the future we may be able to see beyond what is now considered the observable universe and find other universes? What do you think?

It just doesn't make any sense how this universe could be the only one. I always thought of the universe/multiverse/omniverse as infinite.

If there is 'nothing' outside the observable universe it would be just black space for eternity, right? Unless the universe is round (which all current evidence points to it being flat) then you can't arrive back in the universe in the other side. Plus most likelly space, like "time" is infinite.

don't you all mean "universe"? the observable universe extends to the Hubble sphere right, but there's no evidence that everything would just stop exactly at the line of Earth's observable universe. that'd place us at the center, which is silly. things seem like they extend for quite some space beyond the sphere we can observe right?

 

[marcus]

... that'd place us at the center, which is silly. ...

You have the right idea. It would be quite silly to limit our idea of the U to an observable sphere around us. Because models which extend beyond that can be tested by what they predict that we can observe.

Restricting our models to the immediately observable range would make them unnecessarily and unreasonably complex. Nobody does it and there would be no justification for it. So you are right. Silly is the correct word.

But you need to check the definition of the Hubble sphere, and be sure what the different horizons mean.

the observable universe extends to the Hubble sphere right,

Actually not Qwe, the observable extends way way beyond the Hubble sphere. The Hubble radius corresponds to redshift z = 1.4, ( BTW that is a proper distance of 13.7 Gly. Proper means freeze-frame, it would be what you would measure by conventional means if you could freeze the expansion process at this moment, and depends on estimated values of cosmo parameters).Anyway we see way beyond z = 1.4. We see millions of galaxies with redshifts larger than 1.4, out to more than z = 7! And the Background has redshift about z = 1090!

When we observe the microwave background we are looking at matter which is now at a proper distance of over 45 Gly. If you could freeze expansion it would take 45 billion years for a flash of light to get from here to the matter that emitted the background radiation we are now receiving. Of course that matter used to be a thousand times closer but that is how far it is now.

By definition the Hubble radius is merely the distance that is expanding at rate exactly c. If a galaxy is right at z = 1.4 then (if it is stationary relative to background) the distance to it is increasing at rate c. If it is farther, with larger redshift, then of course the distance is increasing at more than c.

The Hubble law v = Hd is defined in terms of proper distances and the current rate they are increasing.

But anyway, just to be clear, the observable is way bigger than the Hubble.

but there's no evidence that everything would just stop exactly at the line of Earth's observable universe.

That's right! It's an important point. It would be foolish to pretend the universe "stops" at a proper distance of 45 Gly (the distance today of the most distant matter we are observing.) In cosmology we work with a mathematical model and our view of the universe is inferred. The standard model certainly does not stop at 45 Gly!
It wouldn't work if it did.

The game in a math science like cosmo is to get the simplest model that fits the data. And nobody I know of uses a bounded model where the U "cuts off" at some observation limit like 45 Gly (proper).

A few (pretty clearly misguided) people might say we OUGHT to only consider the universe what we can see in real time----mathematical inference based on model-fitting should not be allowed, they imply.
Heh heh, but almost NOTHING is being eyeballed real-time. A dragon could have eaten everything out beyond redshift z = 0.1 yesterday and we wouldn't know it for a long time!
Almost everything we can say is based on inference using a model (which has been tested every way we can think using all the data we can scrape up!)

We infer how things are nowadays from light we are getting now that was mostly emitted long ago. Strictly speaking that is mathematical model based inference, and relies on the simplicity of the model. You could always postulate a dragon who has moved things around or eaten a bunch of stuff, so that the real U is different from what we infer, but putting in the dragon would complicate the model.

Same way with putting in a boundary with a cutoff at some distance like 45. It would just make things more complicated and there is no reason to do it.

 

[Flatland]

In other words it is more in the realms of philosophy right now. But don't you think in the future we may be able to see beyond what is now considered the observable universe and find other universes? What do you think?

It just doesn't make any sense how this universe could be the only one. I always thought of the universe/multiverse/omniverse as infinite.

If there is 'nothing' outside the observable universe it would be just black space for eternity, right? Unless the universe is round (which all current evidence points to it being flat) then you can't arrive back in the universe in the other side. Plus most likelly space, like "time" is infinite.

If the universe is infinite then there will just be more stars and galaxies beyond the observable universe.

 

[marcus]

If the universe is infinite then there will just be more stars and galaxies beyond the observable universe.

I agree, Flatland. The basic premise in cosmology is matter distributed uniformly. The so-called "Cosmological Principle" that Einstein stated in a 1917 paper on cosmology. Then restated in a paper in 1931. It was first called that in 1935, I believe

As long as we have no reason to think otherwise, we assume the Universe is just more of the same in every direction. And that makes the models simple, because no edges to worry about.

It's kind of a Copernican idea---that we aren't special and our location isn't special. But it's more important than just ideas, it makes the math simple and makes the model work right. And it continues to check out pretty well, at least to first order approximation. Can never be sure of course.
=========================
A good exercise in this connection is to use one of the online calculators to find the distance to the surface of last scattering. This is basically the location of the matter that emitted the radiation we detect as microwave background (the socalled CMB).

The CMB has an estimated redshift z = 1090. So for instance you google "cosmo calculator" and get Ned Wright's online calculator and put 1090 in the z box.
You get that the proper distance (the kind that goes into Hubble law) is 45.6 billion light years. The light travel time (a time, not a distance) comes out to be 13.7 billion years. That is sometimes called the "look-back time". Because of expansion, the lookback time is not readily convertible into the distance and shouldn't be confused with it.
Here's a quote from the calculator output:

=====quote Wright's cosmo calculator==

For H_o = 71, Omega_M = 0.270, Omega_vac = 0.730, z = 1090.000

It is now 13.666 Gyr since the Big Bang.
The age at redshift z was 0.377 Myr.
The light travel time was 13.665 Gyr.
The comoving radial distance, which goes into Hubble's law, is 13995.7 Mpc or 45.648 Gly.
===endquote===

 

[Chronos]

Most modern cosmological models limit the extent of the observable universe to one that has an observed [and model dependent] limit of about 13.7 billion light years from earth. At that point your hit a wall called the surface of last scattering. We are currently unable to observe more ancient/distant entities. There are theories suggesting there may be more than we can currently observe, but, none have observational support to date. Marcus is better acquainted and frequently posts on this very interesting topic.

 

[jreelawg]

Let's rephrase the question. What is beyond the observable everything? That doesn't even make sense. There is no observable universe. The universe includes both observable and the unobservable. Taking all we see and calling it the universe is dumb. Lot's of cosmologists do this and it is annoying. Some of them have the decency to at least say observable universe which as I pointed out makes no sense also, but at least I can understand what they intend to say.

 

[marcus]

Let's rephrase the question. What is beyond the observable everything? That doesn't even make sense. There is no observable universe. The universe includes both observable and the unobservable. Taking all we see and calling it the universe is dumb. Lot's of cosmologists do this and it is annoying. Some of them have the decency to at least say observable universe which as I pointed out makes no sense also, but at least I can understand what they intend to say.

I agree that it is silly--or as you say, "dumb"--to say universe when what you mean is just the observable portion. My favorite cosmology prof at Berkeley was very careful about this---always said "observable universe" when he meant just the that limited portion. My impression is that most others, professionals, are equally careful but I couldn't swear to it.

It strikes me as either misleading or crackpot to insist on a nonstandard terminology, where only the directly visible portion is treated as the whole. Except when talking to journalists or to a lay audience I can't think of any working cosmologist who makes that mistake.
I could be wrong though, you may have encountered that more than I have.

We do get a small amount of it here at PF though. Most people are not confused, I hope.
A kind of mild ineffectual trolling---best thing could be to simply ignore.

 

[MotoH]

Wouldn't the non-observable universe be everything and nothing? Since electrons can take all paths to a given point, and only chooses a specific path once it is observed, shouldn't anything beyond our observations be either here nor their?

Am I out of line in believing this?

 

[marcus]

Wouldn't the non-observable universe be everything and nothing? Since electrons can take all paths to a given point, and only chooses a specific path once it is observed, shouldn't anything beyond our observations be either here nor their?

Am I out of line in believing this?

Well you could be getting quantum mechanics mixed up with classical concepts here

Words have different meanings in different contexts. The observable universe in cosmology is a CLASSICAL idea (not quantum mechanical). It is a big spherical region a ball with us at the center. Full of all the matter from which we could be currently getting light and other signals (neutrinos, gravity waves...)

Or in 4D you can think of it as contained in our backwards lightcone.

=======================

In Quantum Mechanics, what passes for observation does not need to involve humans, or even consciousness. It is a very general idea. A particle can be forced to choose simply by interacting with other particles---with its environment.

For us, the most distant matter that we get light from is at the socalled "surface of last scattering"---currently about 45 billion light years away.
That's the distance you would measure if you could stop the expansion process now and use conventional means. Sometimes called the now distance, or the current proper distance.

Don't think of the stuff that is out beyond 45 Gly as somehow "fuzzy" just because WE are not out there to see it We aren't that important.

 

[hurk4]

existence, whatever that is!
hurk4

 

[marcus]

existence, whatever that is!
hurk4

Heh heh, good to hear from you, Hurk!
Sounds like you hit the nail on the head.

Or how about this: "what is beyond the observable universe?"
"The unobservable universe."

 

[iflexit_1]

Perhaps an easier explanation is available, premised in GR. In General Relativity, space is dynamic. It can expand, shrink and curve without being embedded in a higher-dimensional space. In this sense, the universe is self-contained. It needs neither a center to expand away from nor empty space on the outside (whatever that is) to expand into. When it expands, it does not claim previously unoccupied space from its surroundings.

 

[Chronos]

If you see it, it is by definition part of the observable universe. The 'unseeable' parts of the universe are, and will always be observer dependent.

 

[aashay]

I think it makes no sense in thinking what is there beyond the observable universe as we cannot visualize it. It is like an ant on a surface of an expanding balloon who cannot imagine anything outside the surface of the balloon.

 

[DarkStar7]

The edge of the Universe is where all matter is expanding away from us at the speed of light. Any energies lost over this universes 'event horizon' is returned back into the quantum realm to drive microbangs that produces dark energy inflation along with all the other properties of the excepted standard
model.


I think if this were true dark energy and an excess cosmic microwave radiation should be more concentrated near large black holes such as our Milkyways super massive one. Is there such evidence?

 

[bapowell]

Most of the accepted hypotheses regarding the origin of the universe (U) refer to it as if we could take a God's Eye view and see it from the perspective of an outsider. For instance, Alan Guth's Inflation postulates an inflaton particle that came into existence as a statistical necessity because it could do so in an extremely high energy state which could then decay into the U that we see. For this to happen, there must have been some sort of meta space and meta time, a metaspacetime.

What do you mean by metaspacetime? How does that follow from your previous point? Low energy inflation can certainly be implemented in the early universe, although many would argue that it's not as natural as high energy inflation.

 

[bapowell]

Where is (or was) the Inflaton particle? We are speaking of it as if it had an existence of its own before it decayed into our universe. If so, there was and is a whole set of dimensions beyond this universe that I call metaspacetime. don't let semantics get in the way. It doesn't matter what we call it. Pythagoras said "All is Number." If we can represent it mathematically, it is real. Somewhere, somewhen.

I think you're misunderstanding the premise of the inflationary universe. The inflaton didn't decay into our universe, rather, it is a field that lived in our universe. It is typically modeled as a quantum field, just like any other. Linde's early chaotic inflation model takes the stage soon after the standard hot big bang. It postulates that the inflaton field existed everywhere in space in the early universe (along with all the other matter and energy from the big bang), with an energy density stochastically distributed in space. Regions of high relative inflaton energy density underwent inflation. The small inflationary patch grew in size to a an empty, homogeneous, essentially flat region. The inflaton field then decays into radiation. This is now the hot big bang from the perspective of the inflated region. In other words, the inflationary patch that eventually grew to form our observable piece of the universe was itself just an ordinary region of space already existing in the universe soon after the big bang.

 

[bapowell]

Lots of physicists still resist the quantum concept as it may apply in the macroscopic world,

Isn't this what decoherence addresses?

 

[bapowell]

Decoherenc is another word for collapse of the quantum waveform upon observation. But, decoherence is just an interpretation according to the Copehagen convention. Wheeler and his students would opt for superposition and divergence of some of the "many worlds" upon any such observation. But is any of this testable?

I don't know if it's testable, that's not the point I was refuting. You claimed earlier that physicists resist the application of QM to the macroscopic world. I was pointing out the decoherence as it applies to the 'qauntum-to-classical' transition is an example of how quantum mechanics is applied to macroscopic objects. I agree that there are several competing interpretation of exactly what all this means, but that's a different matter entirely from whether or not QM, at least phenomenologically, is applied to the macroscopic world.

 

[hurk4]

Heh heh, good to hear from you, Hurk!
Sounds like you hit the nail on the head.

Or how about this: "what is beyond the observable universe?"
"The unobservable universe."

Dear Marcus, thank you for your kind remark.
My answer "Existence" was the most general I could imagine, but what can we do we this "non practical" remark, I guess almost nothing.
I could eventually fill in more details at the price being speculative.
So I could for instance add "coherence with our observable universe".
Glad to see that Martin Bojowald came with a book "before the big bang" in german language also translated in dutch language year 2009. This of course is his view on what is beyond.
I must also remark to you that the (our) unobservable universe is partly observable by a virtual observer near the edge of our observable universe and so on until there might eventally/(inevitably?!) be a real event horizon for our domein of the universe .
kind regards,
Hurk4

 

[ChrisHG23]

Hi,
This will be my first ever post. and I apologise of its wrong but,...

It seems to me the universe is only flat because like fish in water we are only able to perceive our realm, and not the whole universe in which our watery realm exists. Outside of the observable universe is the rest of time, either left behind, or yet to come. I see the universe as an infinite singularity in which our experiences are relative points formed from the balance between the infinite expansion and contraction of time, space and the universe as a whole. The Big Bang was also a Big Crunch and it's is still happening beyond the boundary of the 'Observable Universe'.

To me 'we' are still shrinking, why else would galaxies spin so fast and Black Holes get so small. This is a product of The BigBangBigCrunch. If THE infinite nothing that has no scale, then the primordial universe could not be limited to form or scale as it would have the infinite spectrum of form and scale to 'evolve', 'grow', 'expand' or 'contract', and it is this relative part of time and space we call home, our universe.

 

[bapowell]

Hi,
This will be my first ever post. and I apologise of its wrong but,...

It seems to me the universe is only flat because like fish in water we are only able to perceive our realm, and not the whole universe in which our watery realm exists. Outside of the observable universe is the rest of time, either left behind, or yet to come. I see the universe as an infinite singularity in which our experiences are relative points formed from the balance between the infinite expansion and contraction of time, space and the universe as a whole. The Big Bang was also a Big Crunch and it's is still happening beyond the boundary of the 'Observable Universe'.

To me 'we' are still shrinking, why else would galaxies spin so fast and Black Holes get so small. This is a product of The BigBangBigCrunch. If THE infinite nothing that has no scale, then the primordial universe could not be limited to form or scale as it would have the infinite spectrum of form and scale to 'evolve', 'grow', 'expand' or 'contract', and it is this relative part of time and space we call home, our universe.

I'm going to assume that this is a joke and that you aren't really looking for an intelligent response to this...