## A variable expansion speed theory of gravity

This is not an everything goes forum, but rather a place to ask questions and request help for developing your ideas.

### Re: A variable expansion speed theory of gravity

Dave, you and I can do a similar experiment (to the one I described to Adrex) on your "flatlander earth". I will place my 3 beacons randomly anywhere on the outside surface, and you (say sitting on the pole, but it does not matter where) can measure the radar distance to all three points and all three their bearing relative to you .

To calculate the sum of the inside angles of my triangle is then easy and hence you know the curvature of "flatlander earth" - it could be positive, zero or positive, but you will know it.

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### Re: A variable expansion speed theory of gravity

Hi Andrex,

Andrex wrote: So you have one angle with a degree and one known length for the each sides of the triangle. You don't need more to find the degrees for the two angles missing.

Are you kidding?

Andrex wrote:To find the length of the arc, scientist know that the brightest microwave background fluctuations (or "spots") on the arc would be about one degree across if the universe is "flat".

Firstly, how do we know such a spot is "ABOUT" one degree? Do any particular spots matter? Are all the spots the same size? Or do we only use those spots we measure from here to be about 1 degree?

The Standard Model doesn't predict Dark Matter and Dark Energy was just recently invented to explain an apparent acceleration in the expansion of the Universe. If I had the Time, I might go and research the actual data used to determine the flatness, but we don't live in 3D space. If we did, we could travel to the CMB. But the CMB is embedded in History, so we can't actually go there.

The CMB doesn't surround us exactly, we surround the CMB since it only exists in history from when the Universe was smaller and hotter. If you think of the CMB as a shell around the Universe, then someone has to be closer to this shell than us. (That's a joke)

Also, how thick is this shell? It must be a Gradient, since it represents a cooling of the Universe. The further we look out into the Universe, the further back in time we are looking, to a time in History when the Universe was a fraction of the size it is today. That may be hard for some to wrap their minds around.

And lastly, you have not shown any understanding of 4D Geometry. As I said, the 3D Surface of a Hyper-Sphere will look flat. In fact, if you had an infinitely fast Laser Beam that didn't disperse and removed all Gravity influences and obstructions, then any direction you shoot the beam, it will hit you in the back, even with the Beam traveling in a perfectly straight 3D line. That's 4D for you.

Whoops, Jorrie and I cross posted. Will respond in a separate post than this one.

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### Re: A variable expansion speed theory of gravity

Hi Jorrie,

Jorrie wrote:you (say sitting on the pole, but it does not matter where) can measure the radar distance to all three points and all three their bearing relative to you.

Radar? Even if I could, I would only get distance values and that tells me nothing about the angles in a blindfolded test from a single point of reference.

Jorrie wrote:To calculate the sum of the inside angles of my triangle is then easy and hence you know the curvature of "flatlander earth" - it could be positive, zero or positive, but you will know it.

That makes no geometrical sense. I still need to know at least two of the angles. If we quarter the top half of a sphere, We get three 90' angles at each outside corner. I can't know that unless I can measure it. I can't measure more than the one corner where I'm located. Radar or Not ;)

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### Re: A variable expansion speed theory of gravity

Andrex » December 20th, 2016, 4:52 pm wrote:Vivian
If our eyes "capture" light from photons, then how can we say our eyes "produce" light? I would have thought the photons were producing the light that our eyes captured. I am perhaps over-simplifying?

You're right; it's not our eyes that "produces" light; our eyes have the ability to capture only a small part of electromagnetism which we call "light". It's "special" only to our eyes; not to electromagnetism. Photons don't "produce" light either; photons are the "particle part" of light; the other part is "ondulation". Both are the causes of electromagnetism and of that portion we "see" as light.

Thank you Andrex. I understand now. Happy Day
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### Re: A variable expansion speed theory of gravity

Hi Dave, me thinks you are thinking of the wrong angles.

Dave_Oblad » 21 Dec 2016, 09:04 wrote:I can't measure more than the one corner where I'm located. Radar or Not ;)

Ok, to make it more concrete, say you and your search radar sit at the pole in "flatlander country", of unknown curvature. To make it easier to calculate, I set up 3 responder-beacons at nice earthly coordinates: B1: 45.0°, -120.0° (North Oregon). B2: 45.0°, -90.0° (North Wisconsin). B3: 27.5°, -105.0° (North Mexico). I then locally measure the distance between each pair of beacons, using whatever means available. I have cheated and used Google Earth to find it is a roughly equilateral triangle with sides around 2350 km each. I mail this info to you.

Now use your search radar to find the distance and angle of each of my beacons from your fixed polar position. See what you get from cheating with Google Earth and check if your values correlates with my values (after some simple trig to convert from your position to mine).

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### Re: A variable expansion speed theory of gravity

You can then use your optical instruments to measure the sum of internal angles of my triangle.

Do you mean that I can, but you cannot?

What is the difference between measuring from which ever angle of the triangle?
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### Re: A variable expansion speed theory of gravity

Andrex » 21 Dec 2016, 17:13 wrote:Do you mean that I can, but you cannot?

What is the difference between measuring from which ever angle of the triangle?

You are outside my triangle and cannot measure any of its angles directly.

I sketched the scenario above in response to Dave_O. This is somewhat analogues to the way cosmologists measure curvature. I'm using the analogy to build up to a common understanding of how this works.

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### Re: A variable expansion speed theory of gravity

I've been looking for "clear" explanations of the process to define the flatness of the universe since Dave brought his objections which, I feel, are important.

This is what I went through before getting "very bored". You can try it if you want:

https://arxiv.org/abs/hep-th/0512148
https://arxiv.org/abs/hep-th/0407213
https://arxiv.org/abs/gr-qc/9408026
https://arxiv.org/abs/0908.0346

Then, I had enough of all that useless "bla-bla". So I came back to the original problem which is:

The flatness problem.

Here is one of the places where to find, of what consists that problem:

MEASUREMENTS FROM WMAP

The WMAP spacecraft can measure the basic parameters of the Big Bang theory including the geometry of the universe. If the universe was flat, the brightest microwave background fluctuations (or "spots") would be about one degree across. If the universe was open, the spots would be less than one degree across. If the universe was closed, the brightest spots would be greater than one degree across.

Recent measurements (c. 2001) by a number of ground-based and balloon-based experiments, including MAT/TOCO, Boomerang, Maxima, and DASI, have shown that the brightest spots are about 1 degree across. Thus the universe was known to be flat to within about 15% accuracy prior to the WMAP results. WMAP has confirmed this result with very high accuracy and precision. We now know (as of 2013) that the universe is flat with only a 0.4% margin of error. This suggests that the Universe is infinite in extent; however, since the Universe has a finite age, we can only observe a finite volume of the Universe. All we can truly conclude is that the Universe is much larger than the volume we can directly observe.

We've seen that that margin of error(for flatness) was diminished greatly with PLANCK results. I must add that "finite age of the universe" does means " non infinite universe" and not "observable finite universe".

Now if you feel that this is an acceptable explanation, good for you; but, basically, the premise to all this is:
Believe it or don’t!

As a matter of fact, I'm not very inclined to "beliefs". So I'll recap.

Scientits say that they see three possibilities for the shape of the universe: 1) flat, 2) close and 3) open.

So what are they talking about here?

It's obvious that they're talking about the "overall shape" of the universe.

This is very impressive, but completely "absurd". Specially that "flat" universe that is presented here. How could the universe we observe exist in that kind of "flat" two dimension universe? (I know; I know; in fact they're presenting the "geometry" of the universe. But why present it that way, without more explanations? It's still ridiculus. Specially since "geometry" is not at all "shape")

First of all what brought scientists to consider those three possibilities in the first place?

The answer is : the critical density. So... what is "that"?

The ‘critical density’ is the average density of matter required for the Universe to just halt its expansion. A Universe with the critical density is said to be flat

"Matter to just halt its expansion" means "attractive matter"; and we know that matter doesn't "attract" anything. It only "deforms" space. So if, ever, matter is the real reason that halts expansion, it means that all the universe is "deformed". Which, we must agree, hardly confirms its "flatness".

On the other hand, if the universe is flat regarless of the matter it contains, it means that there's not enought matter existing to deform all of the universe. Luckily for everybody, there's less of 5% of matter in the total universe. The rest is space of which the majority is "flat" up to a ridiculus degree of "non-zero flatness".

Furthermore, we now know that expansion is accelerating. So, not only is the quantity of matter insuffisant to halt expansion, the universe is in accelerating expansion without the slightest sign of being "open". Universe still stands "flat" whatever previous interpretations are presented.

There's only one solution to all of this (and it's not dark matter and dark energy to make us accept previous errors): Our universe has been flat since the beginning ( which is perfectly normal) and whatever quantity of matter occupying space, doesn't have any consequences on this "flatness" or its accelerated expansion (all which is observed). These are simple "facts" that cannot be overun.

Anybody have anymore problems on the subject?
Because, then, at least, we will be talking about "facts"; and not about enterpretations based on erronneous or imaginative ridiculus informations.
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### Re: A variable expansion speed theory of gravity

Hi all,

Good points Andrex.

I still have an issue with Jorrie's analogy, because he is allowing me knowledge I can't have.

Given a Triangle where I am only allowed to know the angle where I am at.. (say 90') I can't know the other two angles unless I can go there and measure them. And I can't. So I would assume in a flat Universe the other two angles would be 45'. But if Larger than 45', then we have curvature. But I don't have the means to go there and measure them. Partly because the CMB is not a wall but rather a gradient without a clearly defined surface. It's a local measurement of our sky.

Also, this analogous wall that "surrounds" us is much much "smaller" than the current size of the Visible Universe. That's kinda cool.

Also, I've said we exist in a 3D Universe that has a 4th dimension. That's where the curvature would be and said curvature would be invisible to us, unless we cold travel out a few light years in a straight line, hang a precise turn, go further, hang another precise turn back home and see if our turns bring us back home. But the Universe is so big, a few light years may not be precise enough. Maybe a few thousand Light Years out in a deep void would work. Not gonna happen tomorrow..lol.

I'm hoping that someday, we will spot two forming Galaxies (or such) and realize they are the same single one, but viewed in opposite directions from us. This won't be easy, because the only way for them to be identical, is if they are on exactly the opposite sides of the Sphere. By "They" I mean "Observer here" and "Target there(s)".

As for the validity of the Curvature being Flat, I'm no expert so I can't say much.. except it is based on a lot of assumptions and ideas that could topple with the next new discovery. That''s Science for you. It's not like Faith.. it changes almost daily.

Best Regards,
Dave :^)

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### Re: A variable expansion speed theory of gravity

Also, this analogous wall that "surrounds" us is much much "smaller" than the current size of the Visible Universe. That's kinda cool.

You get me there! Since that "wall" is caused by the liberation of "visible" photons, I don't understand what bigger part could be "visible"?

Also, I've said we exist in a 3D Universe that has a 4th dimension.

My opinion:
3D = pratically (a fact)
4th dimension = mathematical necessity; nothing more.

... and realize they are the same single one, but viewed in opposite directions from us.

And what direction would that be? All I can see around us is...the past.

This won't be easy, because the only way for them to be identical, is if they are on exactly the opposite sides of the Sphere.

It,s not that hard to see. You can see it on PLANCK photo of the universe; whatever place you pic is the opposite of the place in front of it starting your pic as the overall diameter of the picture; and you'll find out that each places are far from identical.

Have fun :-)
Andrex
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### Re: A variable expansion speed theory of gravity

But Dave, you have lots of information that you can determine from your polar spot, in order to characterize my distant triangle.

To save you time, I'll give your radar values that I got form G-Earth: B1: 5000 km at bearing -120. B2: 5000 km at bearing -90. B3: 7000 km at bearing -105. All approximate, but good enough for this exercise and taking Greenwich as bearing zero from you. Note, these are all values that you can observe from the pole.

When you do the trig from your perspective and assuming zero spatial curvature, you will find my triangle to be not quite equilateral, but more importantly, with some 10% longer sides than what I have observed locally, e.g.

Dave_O - Jorrie Experiment

The black triangle is my part and the blue kite (length 7000 km) represents your observations and calculations.

What conclusions can be drawn from this situation?

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### Re: A variable expansion speed theory of gravity

Andrex, just a little hint on quoting posts: please include in the quote at least part of the name of the member that you are quoting. The proper way is to give a link to the reply from which it comes, e.g. in this post. In some of your prior posts, it is unclear where the quoted texts come from.

The code looks like this:
Code: Select all
`[quote="[url=http://sciencechatforum.com/viewtopic.php?p=312537#p312537]Andrex » 21 Dec 2016, 17:13[/url]"]`

It's easy if you just quote from one post, because the "quote" button top right does exactly that, but then for the whole previous reply, which is not good. I just delete the pieces I do not want. If quoting from more than one post, I just use the "quote" tag in the editor and then write e.g. ="Andrex" inside the opening quote tag, e.g.
Code: Select all
`[quote="Andrex"]Paste in a piece of copied text...[/quote]`

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### Re: A variable expansion speed theory of gravity

Hi Jorrie,

I think I get you now. If I assume the wall to be perfectly radial but get a difference in distance from three points on the wall, then the difference must be due to 4D curvature? I would have to use the difference in red shift from 3 points to decide distances. Since the wall is not completely homogeneous (thermally speaking) I would need a lot of samples in an average area to draw any reasonable conclusion. I like that. Makes sense.

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Dave :^)

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### Re: A variable expansion speed theory of gravity

Hi Andrex,

If I was at the North Pole and my line of sight wrapped around the Earth and distance from my location represented looking into the past, then I would have an Event Horizon limitation based on Time. If we pretend that Event Horizon was the Equator then yes.. I would never be able to see anything south of that. But where would the event horizon be if we realize the size of the Universe was much smaller back then? I think it would push the Event Horizon further south. The better the telescope, the further back in time we can view. Could there be any features visible looking south (back in time) far enough that might be visible, regardless of the direction we choose to look? A bit like looking at the CMB through a Telescope for greater details.

That I don't know. Probably not.. but it's still a cool idea.

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Dave :^)

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### Re: A variable expansion speed theory of gravity

Hi Dave

Dave_Oblad » 22 Dec 2016, 11:11 wrote:I think I get you now. If I assume the wall to be perfectly radial but get a difference in distance from three points on the wall, then the difference must be due to 4D curvature?

You are jumping ahead too far now, becasue I'm not sure that we communicate on my example yet. Remember, those 3 beacons are all on your "2D flatland", where there is no up or down, just a surface on which light and everything else lives. Beacon 3 is 7000 km from the pole and the other two are 5000 km, curved surface or not.

The implication is that although you cannot "see" that your 2D flatland is curved, you can make selected remote measurements to determine if the flatland surface is curved or not. In the example it is positively curved, because you measure a larger triangle than what I do. If flatland had zero spatial curvature, our two measurements would have agreed (in terms of the length of the triangle's sides).

The situation is much more complex when we go to curved 3D space, but one must get a good grip on curved 2D space first. From the pole, you are not really measuring the curvature in the region of my USA-Mexico triangle, but rather the overall curvature between you and the triangle.

If we now jump to the CMB: in observing points on the CMB (surface of last scattering, all with the same redshift), we are not measuring the curvature of that surface (it is actually negatively curved) - we are measuring the overall curvature of the space between us and that surface, just like your measurement from the North pole was measuring the overall curvature of Earth.

When we do that sort of measurement on the CMB, we find the equivalent of "your polar measurement of my black triangle gives the same side-lengths as my local measurement" - hence the overall spatial curvature of space is zero to within observational uncertainties.

The real cosmological process is not that simple, but we are just trying to get our heads around the concept here. I hope this clears up some of the issues - otherwise, shout for more details ... ;)
Last edited by BurtJordaan on December 22nd, 2016, 7:10 am, edited 1 time in total.
Reason: added: (it is actually negatively curved) - see above

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### Re: A variable expansion speed theory of gravity

by Dave_Oblad » December 22nd, 2016, 4:49 am

But where would the event horizon be if we realize the size of the Universe was much smaller back then?

It would be as if, of instead of being on Earth, you'd be on the Moon. You couldn't see further than the equator (so nothing "new"). But then, all you'd have to do is change place on the moon to se further toward the south pole; which doesn't apply in the universe.

But we are still discussing as if the universe was "curved"; which it is not (enough) to do.

Could there be any features visible looking south (back in time) far enough that might be visible, regardless of the direction we choose to look? A bit like looking at the CMB through a Telescope for greater details.

The only "further" we can see, is before 380,000 after BB; which means: see through the CMB "light wall". And that will need a "neutrino telescope". And you would, again, still see back in time. I don't think we could see before time began :-)

As for seeing further "back in space", there mustn't be very much "space" to look at, before "time began". Specially since, time began before "space volume" appeared.

by BurtJordaan on December 22nd, 2016, 5:43 am
but we are just trying to get our heads around the concept here. I hope this clears up some of the issues

It does; thank you. I'm beginning to understand your point and I like it. :-) Still studying it though.
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### Re: A variable expansion speed theory of gravity

Something relevant to cosmic horizons from LightCone 7.

R is the Hubble radius, Dhor the cosmic event horizon and Dpar the particle horizon, a.k.a. the radius of the observable universe. A little more definition can be found in the tooltips under the <Open Column Definition and Selection> button of LightCone 7.

As one can see, all of them essentially start at radius zero at 'time zero'.

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### Re: A variable expansion speed theory of gravity

Very interesting; thank you Jorrie

Dpar (particle horizon) seems to have "expanded" in a straight line since "time zero" wherever they might actually be.

Dhor:Info:

Note: Examples of cosmological models without an event horizon are universes dominated by matter or by radiation. An example of a cosmological model with an event horizon is a universe dominated by the cosmological constant (a de Sitter universe).

So according to PLANCK composition of our universe (5% baryo-matter, 25% Dark matter and 70% of Dark energy (radiating)) it shouldn’t have an event horizon; no?

R info: Current observations place the Hubble constant at around 71 km/s/Mpc, which gives a Hubble radius of 13.7 billion l.y. But in fact, PLANCK as calculated it at 67,15 km/s/Mpc so the radius, in reality, is even shorter than 13,7 bly. And that would be the radius of the “observable universe. Wouldn't it?

Furthermore, it seems that Dhor and R could merge in the future.???
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### Re: A variable expansion speed theory of gravity

I'm glad that you find it interesting. The calculator is in fact a nice tool, once one gets used to it. It was originally intended to be quite simple, but under encouragement from the late Marshall (RIP), it has eventually grown into somewhat of a handful...

Andrex » 22 Dec 2016, 17:30 wrote:Dpar (particle horizon) seems to have "expanded" in a straight line since "time zero" wherever they might actually be.

Initially, during radiation and matter dominance yes, but later during cosmological constant dominance, it starts to slope upwards. One needs to look at the math to get a good grip on why, but playing around with the range of the curves, one can visually see that.

So according to PLANCK composition of our universe (5% baryo-matter, 25% Dark matter and 70% of Dark energy (radiating)) it shouldn’t have an event horizon; no?

The %'s that you quoted are rough cut values. The cosmological constant dominates and is equivalent to vacuum energy, do this does give us an event horizon, with present value around 16 Gly, larger than the Hubble radius, which is 14.4 Gly presently.

But in fact, PLANCK as calculated it at 67,15 km/s/Mpc so the radius, in reality, is even shorter than 13,7 bly. And that would be the radius of the “observable universe. Wouldn't it?

Nope, the observable universe is the same as the particle horizon, presently around 46 Gly in radius.

Furthermore, it seems that Dhor and R could merge in the future.???

Yup, they will 'merge' at around 17 Gly radius in the far future.

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### Re: A variable expansion speed theory of gravity

but later during cosmological constant dominance, it starts to slope upwards.

PLANK says that in 10Gly cosmological constant (Dark energy) will compose 93,4% of the universe. Does that mean that there won't be anymore "radiating" in the universe?

The %'s that you quoted are rough cut values.

There's so much differences between them that I don't think it matters. :-)

The cosmological constant dominates and is equivalent to vacuum energy

And vacuum energy doesn't "radiate"; right?

But in fact, PLANCK as calculated it at 67,15 km/s/Mpc so the radius, in reality, is even shorter than 13,7 bly. And that would be the radius of the “observable universe. Wouldn't it?

Nope, the observable universe is the same as the particle horizon, presently around 46 Gly in radius.

Hummm. But the CMB is at 13,7 Gly in radius; and the more we could ever "observe" cannot be more than 380,000 light-years before that??? You're implying that we cannot observe all of "observable universe???
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### Re: A variable expansion speed theory of gravity

Andrex » 22 Dec 2016, 19:11 wrote:PLANK says that in 10Gly cosmological constant (Dark energy) will compose 93,4% of the universe. Does that mean that there won't be anymore "radiating" in the universe?

And vacuum energy doesn't "radiate"; right?

Correct, but there will still be CMB radiation in 10 Gy time, but the redshift would have doubled and it's intensity would have dropped 4-fold.

But the CMB is at 13,7 Gly in radius; and the more we could ever "observe" cannot be more than 380,000 light-years before that??? You're implying that we cannot observe all of "observable universe???

No, the CMB is ~13.7 billion years old. For as much as we can trust our best cosmological model, it is presently more than 45 Gly from us and that distance grows by over 3 light years per year.

J

PS: Sorry, I clicked "submit" instead of "preview" when I had to run on an errand, so it is not a very complete reply; will write a little more later.
Last edited by BurtJordaan on December 22nd, 2016, 2:21 pm, edited 1 time in total.

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### Re: A variable expansion speed theory of gravity

Hi Jorrie,

Jorrie wrote:you can make selected remote measurements to determine if the flatland surface is curved or not. In the example it is positively curved, because you measure a larger triangle than what I do.

That's where I lose you. If I'm at the North Pole.. where are you? I assumed you are standing next to me and thus would get the same values.

If we remap the problem to the CMB and I'm on Earth.. where the hell are you? (lol)

Ok.. I need to read the rest of this thread posted between my visits.

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Dave :^)

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### Re: A variable expansion speed theory of gravity

Hi Dave, I'm in the USA on flatland, so we are at some 5000 km apart.

In the CMB? I am the CMB... ;)

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### Re: A variable expansion speed theory of gravity

Hi Andrex: here's the part that I skipped last time.

Andrex » 22 Dec 2016, 19:11 wrote: You're implying that we cannot observe all of "observable universe???

No, in principle we can observe everything from the end of inflation that ever formed part of our observable universe, throughout its eons of evolution. This means everything that was ever in our past light cone, the red curve (Dthen). As you can see, the green particle horizon was inside our light cone, up to about 1.7 billion years and inside our event horizon until around 4 billion years.

Cosmic horizons and past light cone (red curve)

Various parts are lost from our view as time goes on, but that would need another post to explain.

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### Re: A variable expansion speed theory of gravity

by BurtJordaan » December 22nd, 2016, 12:35 pm

And vacuum energy doesn't "radiate"; right?

Correct, but there will still be CMB radiation in 10 Gy time,

OK (CMB is electromagnetic "radiation"); but the following is the composition (ingredients) of our universe at different epochs according to the results of Planck (2015) given by CNRS :

As you can see, 380,000 years after Bb (CMB)there was 13,9% of "radiating" (light blue portion : whatever this means is irrelevant for now; let's just say that it's not CMB electromagnetic "radiation" because of its next quantity.)

2 billions years after Bb there only remained 0.1% of that "radiating" + neutrinos (I made a mistake writing "2 Gly"; it "2 Gy"; same as 10 Gy)

Today, there's no more of that "radiating" whatever it was.

and in 10 billions years from now 93,4% of the universe will be Dark energy (which is that "vacuum energy" you talked about and said equivalent to "Cosmological constant"), plus 5,6% of Dark matter and 1% of baryonic matter.

So; what infos should we take seriously for exact facts?

Further more, if the "radiating" (before inflation that started at 10^-36 sec after t = 0) is responsible for "expansion" (there was "expansion" before "inflation"), there's no more "expansion" today according to CNRS interpretations of PLANCKs results. Which is ridiculous (and so is three names for the same thing meaning: Dark energy).

Various parts are lost from our view as time goes on, but that would need another post to explain.

I guess you'll have to explain; because if parts are lost from our view, either it's not part of our observable universe anymore or it's not lost of our view.

As for the distance of CMB from us (its radius), PLANCK satellite made the picture we have by "capturing" photons that started 13,7 billions years ago; so the image of CMB we look at, today, cannot be farther than 13,7 light-years from us, because photons can't go faster than light-speed. Consequently, whatever progression was added by expansion after the departure and during the journey of the photons we captured, is not "observable" by us YET (and not ANYMORE).

Naturally, that is assuming that photons really "travel"; which is not necessarily a proven "fact". In reality, if photons "travel" you'll have to explain the "fact" that we can "capture" that photon at different "wavelenght" we choose to look at it (whatever the distance); because according to infos, it's expansion that "expands" electromagnetic wavelenghts.
Andrex
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### Re: A variable expansion speed theory of gravity

Andrex, can you please give a link to the picture with the %'s, because the one you posted does not read very clearly. I spot some problems with the values, but it maybe becasue I can't really see what's what...

BurtJordaan
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### Re: A variable expansion speed theory of gravity

Andrex » 23 Dec 2016, 08:54 wrote:
Burt wrote:Various parts are lost from our view as time goes on, but that would need another post to explain.

I guess you'll have to explain; because if parts are lost from our view, either it's not part of our observable universe anymore or it's not lost of our view.

Yea, I was a little loose in that statement, because in a way I'm describing an oxymoron: 'observable universe' means the part of the universe that we could have received signals from before the emitters have moved over our cosmological horizon. We cannot receive any new signals that they send today. In fact, most galaxies that we still observe lie beyond the cosmological horizon today, but they were all within the horizon for some time in the past.

As for the distance of CMB from us (its radius), PLANCK satellite made the picture we have by "capturing" photons that started 13,7 billions years ago; so the image of CMB we look at, today, cannot be farther than 13,7 light-years from us, because photons can't go faster than light-speed.

Yes, and those photons stared out only 41 million ly from us, but that distance has expanded 1090 times, so the "origin location" of the CMB is today 45 billion ly from us (becasue the redshift of the CMB is about 1090).

The photons (or rather light waves, becasue GR does not know or care about photons) moved steadily at 'c' against the local spacetime, but in the beginning the expanding space dragged light away from us at a pretty huge rate. Only when the dominant matter density slowed the expansion down enough, could light start to make headway towards us.

This can all be studied by LightCone 7's charts, without bothering about the math behind it.

BurtJordaan
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### Re: A variable expansion speed theory of gravity

by BurtJordaan on December 23rd, 2016, 5:38 am
Andrex, can you please give a link to the picture with the %'s, because the one you posted does not read very clearly.

Sure!

http://public.planck.fr/resultats/251-p ... en-quoi-ou

But you could "zoom in" on the picture I sent; no?

“'observable universe' means the part of the universe that we could have received signals from before the emitters have moved over our cosmological horizon.”

Ok; that takes care of the “anymore” part of the observable universe; but it means that the "present time" of those light waves passed beyond our own "present" time. I'll have to think about it; because it implies that "time" is not "distance" and vice versa. It even means that the "present" is not the center of all the "past" around it. Now, what about the “not yet” part?

“In fact, most galaxies that we still observe lie beyond the cosmological horizon today,”

Are you asking me an “act of faith”? :-) But I understand: the space between “what I see today” on Planck, which was 13,7 light-years away, 13,7 billion years ago, as expended during 13,7 billion years. So today, this “what I see” is, actually, far further than it was at the time. But it doesn't fit with your 41 million light-years starting point. (always with the premisse of a "traveling" photon, or lightwave, mind you).

and those photons stared out only 41 million ly from us; but that distance has expanded 1090 times

This is a little more difficult to accept. You’re saying that a photon “cruising” at light speed, started 41 million light-years (that's 12,5 parsecs compared to 1 Mpc = 1000 parsecs) from us and took 13, 7 billion years to cover the distance. Do you have an idea of the expansion rate that would take? At first glance that is ridiculous because the two feet around the volume of a megaparsec (hubbles metric), containing an object, cannot go faster than light-speed whatever the expansion rate is (in fact, the speed of that "two feet" is, presently, around 34 km/sec). We mustn’t mix the “appearance” of events, with the “factual” event.

On the other hand, what we "see" is actually the "appearance" of the event and not the "fact"; but I won't say it before you explain clearly the "fact". :-)

Furthermore, to accept all of this, the "space" we are "in" today, would have to be existing at the time of the CMB. The only answer to that problem is to install us in the "constant present". And that demands that space expansion always appears in our "past".

The photons (or rather light waves, because GR does not know or care about photons) moved steadily at 'c' against the local spacetime, but in the beginning the expanding space dragged light away from us at a pretty huge rate.”

Then I really think that GR should care about the photons. What permitted the space to drag light away from us at a time that our space didn’t even exist?

“Only when the dominant matter density slowed the expansion down enough, could light start to make headway towards us”

And that "downed density" happened 380,000 years after the Bb; which means, if the CMB was 41 million light-years from us at the start, that the “space” covering that lap of time of 380,000 years is, today, a lot "thicker" than 380,000 light-years. And …that.., is definitely ridiculous. Sorry.

Furthermore, if "expansion" appeared before "inflation", why would "inflation" be limited to a "fixed period of time" when time itself expands?

“This can all be studied by LightCone 7's charts, without bothering about the math behind it.”

The problem is neither the chart nor the maths; it’s my …brain. I humbly say. :-)
Andrex
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### Re: A variable expansion speed theory of gravity

Tx for the link. The picture is clear in the report and my calculator(s)[1] agree with all the figures of their 2013 Planck results. It changed very little to 2014 so I did not bother to update the calculator's default values. (The figure in your post did not have the resolution on my screen to help with zooming in).

Andrex wrote:I'll have to think about it; because it implies that "time" is not "distance" and vice versa. It even means that the "present" is not the center of all the "past" around it.

Yes, this is the case in curved spacetime of the cosmos. Remember "spatially flat" does not mean flat spacetime. Our present universe has negatively curved spacetime, because of the accelerated expansion.

Andrex wrote:Are you asking me an “act of faith”? :-)

Only faith in GR and its solution that describes our universe extremely well - except for the very, very early quantum-like universe.

But it doesn't fit with your 41 million light-years starting point. (always with the premisse of a "traveling" photon, or lightwave, mind you)

I don't understand why you see a problem - this is pretty standard modern cosmology (and GR, for that matter). Or do you disagree that if we see the CMB redshifted by a factor 1090 that it was 1090 times closer to our location when the photons started?

How much of this is fact? Only the redshift and the CMB characteristics that we directly measure. The rest is based on our model, which predicts other things just about perfectly...

-J

[1] I have another (older) calculator on the web, preceding LightCone. It was simply called "CosmoCalc_20xx".

BurtJordaan
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### Re: A variable expansion speed theory of gravity

Remember "spatially flat" does not mean flat spacetime.

Sorry; but I can't remember what I don't understand. To me, there's no way you can have space without time. In other word, "space" (distance) is the same thing as "time". For example eight minutes is the same thing as the distance between my eye and the sun and neither one of them can be changed without changing the other one the same way. If one is "flat", the other can't be "curved" (negatively or positively). Furthermore, time and distance react the same way in a volume of deformed space-time.

Only faith in GR and its solution that describes our universe extremely well

Sorry; even that kind of "faith" I can't have.

Or do you disagree that if we see the CMB redshifted by a factor 1090 ...

It sure gets me to ask questions on the "real" effect and source of the redshift. Like I said, no "faith" anywhere.

How much of this is fact? Only the redshift and the CMB characteristics that we directly measure

I agree on CMB being a "fact". I also add light-speed being a "fact" and space-time deformations responsible for gravity. To me, those are "facts". But I'm starting to question myself on "redshift" which is a simple "interpretation".

Like I already mentioned, if "redshift" is the "product" (or consequence) of increased wavelength by the space-time "expansion", how come we can "observe" CMB (for example) by "capturing" in all wavelength?
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