Are Proto-Photons the Only Matter at the Outer Limits of the Universe?

[foolosophy]

Photons were trapped within the early stages of the expanding Universe.

When the early universe expanded to a critical size (or cooled to a critcal temperature) photons escaped their dense enclosure.

Today, these proto-photons must be still moving and located at the furthest limits of the universe which is still expanding.

Can we assume that the outer limits of the universe contain only proto-photons and by definition are void of any baryonic matter?

 

[mathman]

I am not sure what you mean by proto-photons. However, the photons that escaped when the universe cooled down are now "visible" - specifically, the cosmic microwave background.

 

[foolosophy]

I am not sure what you mean by proto-photons. However, the photons that escaped when the universe cooled down are now "visible" - specifically, the cosmic microwave background.

I just made up the phrase proto-photons as a way to define the first photon(s) to be released by the big bang event.

I did consider other particles such as nutrinos but even they possesses a small mass.

So I am assuming that the first particles/waves to be released are massless photons.

These photons are still moving out and lengthening their wavelengths with time.

They must be the furthest entities in the expanding universe - and within these outer limits of the universe there exists a massless state comprised only of stretched out photons.

True?

Not sure

(The CMB radiation has been detected. The Big bang model predicted its existence and in fact predicted the temperature of this radiation to be very cold at about 5 K. We know that the CMB radiation is detected in every direction the detectors are pointed at. Where is this CMB radiation? I think the proto-photons are located in an outer skin of the Universe which is still expanding - is this region massless?)

 

[Chalnoth]

You're assuming that there is an edge to the matter in our universe, beyond which is empty space into which our universe is expanding. This cannot be the case. If you take a flat FRW universe and compare the Schwarzschild radius to the Hubble radius, you find they're the same. For a larger universe, the Schwarzschild radius grows much faster with distance. This means that if the matter were to abruptly end somewhere, from the exterior of the matter, our universe would be a black hole. Thus it is impossible for our universe to expand into empty space.

 

[marcus]

... We know that the CMB radiation is detected in every direction the detectors are pointed at. Where is this CMB radiation? I think the proto-photons are located in an outer skin of the Universe which is still expanding...

F.,
Chalnoth is quite right. You mustn't imagine the universe as something that is expanding out into unoccupied space---something with an "outer skin".

What you call the "protophotons", simply to be detected, must be right here with us. As I recall there are about 410 million CMB photons in every cubic meter. As far as we know they are uniformly distributed throughout the space between the planets of the solar system and between the stars. There is no region that has significantly more than its share.

You may have been confused by imagining the big bang as an explosion outwards from some central region, out into empty space. Often newcomers do have this misconception.

One way to "reprogram" your imagination with a different image is to google "wright balloon analogy" and then make a simple change in the URL which I'll tell you.

When you google "wright balloon analogy" you will get a UCLA website of someone who teaches cosmology---a java animation there of expanding 2D space.
http://www.astro.ucla.edu/~wright/Balloon.html
To make that work for you, you have to imagine that for a 2D animal on the balloon surface, "inside" and "outside" of the balloon do not exist. All existence is concentrated on the 2D surface.

when you google that, you get http://www.astro.ucla.edu/~wright/Balloon.html but don't stop there!
to get more from it, you need to manually add a two at the end of Balloon, to make it Balloon2.
http://www.astro.ucla.edu/~wright/Balloon2.html
Then you will get photons added to the picture! These are analogous to the CMB photons in our universe. They are approximately evenly distributed throughout. There is no "outer skin" where they congregate. They are mixed in with the galaxies (white whirlies).

The only difference is the galaxies stay at the same longitude latitude position on the sphere, as it expands. And the photons (the colored wigglers) change position.

It can be illuminating to simply watch the animation. Restart the expansion a few times, by clicking on the picture.
You can see that in a sense the galaxies "ride the expansion" (and don't changes long/lat position) whereas the photons are mobile in two senses, they ride the expansion but the also travel at a fixed rate, like three(?) millimeters per second.

You will see the wrigglers (the photons) gradually get longer in proportion as the universe expands. This is to symbolically indicate how their wavelength increases over time (as someone on one of the galaxies would measure it.) Ned Wright also makes them change color over time---which is another symbolic reminder that they are being redshifted.

 

[foolosophy]

Chalnoth and Marcus,

Thanks for your comments.

I am aware of the boundary-less condition of the universe (for finite or infinite models)

At that moment when the expanding/inflating universe sufficiently cooled enough to release photons, the Universe had a geometry and finite size (this moment was approximately 300,000 years after the initial big bang event, I think).

Shouldn't the universe be expanding at the speed of these proto-photons? (c)

Estimates of the universe's age from the WMAP data put it at around 13.7 billion years.

Modelling suggests that the outer limits of the Universe are about 95 billion light years away.

What is going on here?

mathematicians are comfortable with their assumptions and conclusions provided they are logically sound and are based on rigorous proof (even if they don't make any practical sense)

 

[Chalnoth]

Shouldn't the universe be expanding at the speed of these proto-photons? (c)

The photons simply go elsewhere in the universe. They don't escape it.

Estimates of the universe's age from the WMAP data put it at around 13.7 billion years.

Modelling suggests that the outer limits of the Universe are about 95 billion light years away.

What is going on here?

The speed of light limitation in General Relativity is a local limitation, because in General Relativity, relative speed is only a well-defined quantity locally. In the most typically-used coordinate system, many galaxies we observe today are now and always have been receding from us at faster than the speed of light.

These galaxies still obey the speed of light limitation in General Relativity, because they never go faster than light rays moving by them. It's just that the expansion rate between us and them is enough that for every meter light moves towards us, there is more than a meter of additional space between us and the photon added due to the expansion.

The reason why we can see many galaxies that are and always have been receding at faster than the speed of light, however, is because the expansion rate slowed down during the first few billion years. So the light left the galaxy, traveling in our direction. But it was left with more additional space still to go due to the expansion. Then, as time went on, the expansion rate slowed. When the expansion rate slowed enough that the light ray could finally start making some headway, it had already traveled quite far from the galaxy. So even though the galaxy was still receding at faster than light, the space the light ray had reached no longer was, so it managed to finally start getting closer again, until it finally reached us.

In this way, light from the CMB which was emitted a mere 42.8 million light years away has taken a whopping 13.7 billion years to get to us. This is because the light, for a long time, lost ground against the expansion. Only when the expansion slowed sufficiently did the light actually start to get closer, and now, 13.7 billion years later, it's here. Today, the matter that originally emitted that light is a whopping 46.6 billion light years away (I'm not sure where your 95 billion light year comment comes from).

 

[foolosophy]

thanks for your reply Chalnoth

(the photons "simply going elsewhere" and not escaping the universe doesn't tell us anything really. the proto-photons or fringe photons can't be in all locations at the same time - no matter how we cling to the stocastic nonsenceness of quantum physics. there must be photons that are further away from us than others - for a reason!)

 

[Chalnoth]

thanks for your reply Chalnoth

(the photons "simply going elsewhere" and not escaping the universe doesn't tell us anything really. the proto-photons or fringe photons can't be in all locations at the same time - no matter how we cling to the stocastic nonsenceness of quantum physics. there must be photons that are further away from us than others - for a reason!)

Further away from us? Obviously. But they're still passing by other matter.

 

[foolosophy]

Further away from us? Obviously. But they're still passing by other matter.

Your statement highlights the point of this thread.

For this to be true, everything must be traveling at the speed of light which isn't the case/

If you were able to imagine traveling to the furthest point in the universe, would there be only a skin of proto-photons in existence?

I can't see how baryonic matter can exist there

 

[Chalnoth]

Your statement highlights the point of this thread.

For this to be true, everything must be traveling at the speed of light which isn't the case/

If you were able to imagine traveling to the furthest point in the universe, would there be only a skin of proto-photons in existence?

I can't see how baryonic matter can exist there

You're still imagining a boundary to the expanding universe, an edge where stuff is expanding outward into empty space. This isn't the case.

 

[foolosophy]

You're still imagining a boundary to the expanding universe, an edge where stuff is expanding outward into empty space. This isn't the case.

I acknowledge the various mathematical descriptions or models of the Universe - all of which are boundary less.

Remember, mathematical concepts (even its axioms) are abstract in nature.

They should and can be challenged when applied to reality.

Are you saying that the Universe has no size? Are you saying that there is no differentiation between the photons at the centre of a 300,000 year old baby universe and at some other point?

 

[Chalnoth]

I acknowledge the various mathematical descriptions or models of the Universe - all of which are boundary less.

Remember, mathematical concepts (even its axioms) are abstract in nature.

They should and can be challenged when applied to reality.

The universe is fundamentally mathematical in nature. Why should intuitive concerns trump mathematics?

Are you saying that the Universe has no size? Are you saying that there is no differentiation between the photons at the centre of a 300,000 year old baby universe and at some other point?

Not necessarily. Yes. In that order.

A closed universe, for example, has a definite size, but no edge. It simply wraps back on itself.

 

[foolosophy]

The universe is fundamentally mathematical in nature. Why should intuitive concerns trump mathematics?


.

This is an excellent point.

Mathematics is a human construct - an artefact of the human mind/imagination.

And on that basis it must be by definition corruptable and inadequate.

Remember, the main conclusions of qunatum theory is that reality (at least in the sub-atomic world) is non-deterministic and stochastic in nature.

And although the predictive power of quantum theory is astonishingly accurate, its conclusions are based upon stochastic or statistical analysis.

What does quantum theory tell us about reality? Does it make sense?

 

[Chalnoth]

This is an excellent point.

Mathematics is a human construct - an artefact of the human mind/imagination.

Not really. You can be quite certain that if we met an alien race, they would have discovered many of the exact same mathematical structures we have.

Remember, the main conclusions of qunatum theory is that reality (at least in the sub-atomic world) is non-deterministic and stochastic in nature.

Still mathematical in nature.

 

[foolosophy]

Not really. You can be quite certain that if we met an alien race, they would have discovered many of the exact same mathematical structures we have.

.

...this is trivial evidence of an underlying mathematical reality. Is this the only basis of your assertion?

Why do mathematical laws collapse under certain conditions and produce meaningless unidefinedness and unresolved singularities?

For that matter, why do mathematicians need more than one definition of infinity?

 

[Svensken]

Hi

As far a i understood the question.
1. You think of a flat and infinite universe, which is a good candidate at the moment.
2. You wonder if there can be matter everywhere in this infinite flat universe.

I have been thinking about this too, if there is matter spread out everywhere in this infinite universe, doesn't that mean that there is infinite energy in the universe?

I might be stupid but could there be a place far far far away where there is spacetime, but no matter? or does the expansion of the universe automatically mean that matter follows with the expansion and thus wherever there is space - there is some matter (excluding by the Heisenberg uncertainty principle there must be energy for small amounts of time)

Im sorry i i sound retarded but its very difficult to formulate my thoughts especially in such a demanding subject.

 

[marcus]

... does the expansion of the universe automatically mean that matter follows with the expansion and thus wherever there is space - there is some matter...

Svensken, I think you are asking an interesting intelligent question, so i hope several other people will respond. It could be answered in several different ways. This is a basic beginner question of a kind that you can ask at the beginning of any mathematical science where the aim is to get the best fit to the most data with the simplest model (and philosophy can go to the devil )

Just kidding, but it is a little like that.

There is a huge amount of data pouring into cosmology. New kinds of telescopes. Automation. Space instruments. The job is to find equations that fit the millions of observations precisely, and among those the simplest, and to measure the 5 or 6 parameters very accurately that must be plugged into the equations, and to keep questioning the assumptions, and to do computer simulations of artificial early universes using the model to see if they evolve into something resembling our real one.

You have identified one of the ASSUMPTIONS of the successful models. That space has no boundary. That matter is approximately uniformly distributed throughout space.

This assumption, also called "cosmological principle", gives the simplest models. Changing it to add boundary, or a gross demarcation where matter stops, makes the model more complicated and we see no evidence for such things. Philosophically IMHO opinion we cannot KNOW that matter is evenly distributed (on average) but it is a simple and successful pragmatic assumption.

Of course that means that if space is finite volume there is a finite amount of matter. And if space is infinite volume there must be an infinite amount of matter. This is OK. As far as I know it does not cause any conceptual or mathematical trouble. Localized infinities are a problem---infinite density, curvature, something that blows up at a particular point. But this is a harmless infinity----a finite density of matter that happens to extend throughout an infinite volume.

It could be interesting to get several different person's answers to this. It is partly a philosophical or foundations issue. Also from time to time there appear reputable scientists who challenge this assumption of borderless uniformity and offer alterative pictures. Like what we think of as universe is just one pocket amongst millions of other universes that we cannot see and it is lethal to come in contact with the separating wall---or else we live in the middle of a low-density void and out in all directions where we cannot see the universe is much denser and this causes accelerated falling, outwards from us. These people are just doing their job because scientists are SUPPOSED to question assumptions and propose alternatives. But so far these radical nonuniform ideas have not made much progress. After a few years each one tends to drop out of sight.

 

[Svensken]

Dear Marcus

Thank you for your great response, it cleared a lot of thing up for me (for now at least)

I now understand what is meant by the cosmological principle somewhat! From what you say it has been the most successful assumption upon which most data has been explained.

This then made me think, that if the universe is infinite in all directions and matter is rather uniformly distributed we can find the same density parameters wherever we observe and thus we could infer the amount of dark energy+dark matter+normal matter+radiation by only looking at say a few thousand parsecs of space? (This seems to me to be very convenient )

This is where the whole issue of where the big bang took place comes into issue right? It is because of the cosmological principle that one must assume that the big bang took place everywhere?

Thanks again Marcus!