The expansion of spacetime is NOT accelerating.
The Mainstream description of the expansion of the Universe is that it is accelerating. This description is erroneous and it is also an improper evaluation of what is observed.

The super “standard candle” – 1a supernovas
When a star explodes as a supernova, over a few days it produces as much light as a 100 billion stars. Type 1a supernovas are a unique type of supernova in that they explode with a very specific amount of mass. The great physicist Chandrasekhar determined that the critical mass for these supernovas is about 1.4 solar masses. Since type 1a supernovas have a fixed amount of mass associated with their destruction, they can serve as “standard candles” to determine distance and since these supernovas are so bright, they can be used to determine extreme distances, more than a billion light years away.

Space is “accelerating”
When it was discovered that type 1a supernovas at a red shift of about .5 or so were dimmer than expected from the assumed rate of expansion, it was concluded by most that they had to be further away, and it was declared that the universe was “accelerating”. Link to supernova group work, here. http://www-supernova.lbl.gov/public/...ysicsToday.pdf

The “unconventional” graph
The graph of the supernova group is in the form the data was taken, magnitude verses red shift. This is an unconventional plot and in order to understand what is really happening has to be translated in to a more familiar form.

Conventional graph of motion
Typically, when a high school physics student is asked to draw a graph describing the motion of an object, the distance traveled is plotted over time. The slope corresponds to the velocity. If the slope is constant, the object is moving at a constant velocity. If the slope is negative (sloping down hill) the object is moving towards the observer and if the slope is positive (sloping up hill), the object is moving away. If the slope has a negative curvature ( a frown shape), the object is decelerating. If the slope is positive, (a “smile” shape) the object is accelerating. Basic physics 101.

Motion is model dependant
It is also important to note that the description of an object accelerating or decelerating is model dependant. The simplest model predicting the rate of expansion of the universe is the Friedman – Einstein model. It assumes the expansion of the universe is Flat, ie poised between expansion and collapse. The expansion would also be the fastest when the universe began, and due to gravitational interaction, the expansion of the universe would slow or decelerate. The expansion of the universe will slow to a stop after an infinite amount of time has passed. A deviation from this predicted rate would be described as a “discovered” acceleration or deceleration.

Conventional graph of expected rate of expansion
The following link leads to a graph I made that describes the expansion of spacetime as expected from the simplest application of general relativity.
http://d77591.u25.existhost.com/gpage15.html (Hope this link works now, "fixed" next day)

Conventional graph of observed data
The following link leads to a graphical representation of the expansion of space, based upon the graphical data provided by the type 1a supernova group’s graph above. The magnitude and red shift values have been translated to a conventional graphical representation of distance verses time. It assumes that 1a supernovas are true constant standard candles.
http://d77591.u25.existhost.com/gpage16.html

Analysis of Graph
A careful review of the second graph is in order. The slope of the graph is always positive, indicating that the galaxies are always moving away from each other. The curvature indicates both acceleration and deceleration. Now lets look at the rates of acceleration over time. Initially the galaxies start off with a high velocity and due to gravitational interaction, the rate of expansion between galaxies slows. This is indicated by the negative curvature (frown shape). Then at about a red shift of .5, (about 3/4 along the x axis), the assumed apparent distance between galaxies is greater, which produces a positive curvature (smile shape). This correlates to an acceleration of spacetime. There is a point of inflection somewhere between the deceleration and acceleration. As we look at the relationship closer to our present era, the rate of expansion is constant, hence the term “Hubble’s Constant”. In order for the indicated positive curvature observed at a red shift of .5 to transition to a 0 curvature (a flat line) there appears to be a negative curvature to form a transition. (Although it may also be an acceleration that is diminishing to 0 without a negative curvature). Technically and exactly, based upon the data in the graph, the universe appears to be first decelerating, then it was accelerating, and then in order to conform to the constant rate of expansion we observe now, the rate of acceleration has diminished so much that the current rate of expansion is constant. .

(It may be argued that the acceleration rate observed at the .5 red shift is just slowing down to a constant rate, and it is still in effect, just at a very imperceptible rate. This is tantamount to admitting the acceleration is imperceptible, and if it is imperceptible it cannot be said the universe is presently accelerating with any degree of confidence. It also does not reflect observation, local galaxies are blue shifted, which could be from gravitational interaction but even if it is gravity causing the blue shift observed with the local galaxies, the physical description of what is observed is consistent with a constant rate of expansion, leaning slightly towards deceleration.)

The second graph corresponds to our observation. Locally, the distance between galaxies varies linearly and as we observe the galaxies further away, they appear to be further away (D is greater).

Is the universe “accelerating”? The graph indicates this acceleration is no longer in effect. The expansion is now very close to being constant.

This is not meant to diminish the significance of the discovery of the dimmer than expected type 1a supernovas. It is a remarkable discovery. The description is misleading, one may be led to the idea that the universe is presently accelerating, when in fact the expansion rate is presently extremely close to being constant, ie “Hubble’s constant” is constant. A careful look at the relationship shows that if there were any “leaning” of the current description of spacetime from a constant rate, it would have to be that of deceleration.

It’s the supernovas that are changing, and not the Rate of expansion.
There is another more significant point to be made and that is regarding the assumption that type 1a supernovas are the same in the past as they are now. If there were some way to explain why younger (more distant) type 1a supernovas are not as bright, it should be seriously considered, especially if they restore the expected simple rate of expansion predicted by General Relativity. Remember, accelerating space results in requiring some new unknown energy source, “dark energy”.

Gravity as a function of Cosmic Time
If the effect of gravity were greater in the past than it is now, then it would not take as much mass to reach the critical pressure for a type 1a supernova to explode. If it takes less mass, then the amount of light emitted would be less, and thus it would appear dimmer. This is what is really happening.

I’ll post some of the figures backing up this statement in less than a week.

So not only is the description of the “accelerating” universe misleading, the justification of “dark energy “ is false.

John M. Kulick
AKA - Snowflake.

P.S. Thank you Tobin Dax. I finally made the graphs. Took awhile since by graphics generator failed.

Shouldn't that just be "space" instead of spacetime? What do you mean, spacetime is accelerating? Isn't accelertation time dependent, in this sense?
Isn't the main justification the rotation curves of the galaxies?

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8) Honestly, Snowflake.... think about this..

Space isnt expanding... BUT... It is trying to... and so looks like it is.

The 4th dimension.... the idea.. a hypercube.. you know.
Balloon expansion...
Moving up and to the side at the same time.. without going diagonal.

4D motion... now, assuming we have a 3D space.. a sphere.
How could we theoretically make it move 4 dimensionally????

By spinning it in 2 directions. giving it 2 spins, on 2 axis, at 90 degrees apart. this yeilds a force at 90 degrees to all the 3 dimensions.
assuming space, as a transindental fluid can move 4 dimensionally, or should i say, is willing to, under the force of applied energy.

do you see it... 4D motion... yields 4 dimensional spatial displacement, and if... and mind you i realise... if.. if... space resists, expansion, if that is the case, that means, that it is possible that the resistance to that expansion would take the form of what????????????????????????

theoretically, Spatial Tension... from the center outward, a tension, formed in direct response to the undersired or impossible motion of expansion.

the spatial tension... is then the fundamental particle.

and as ive pointed out, following this line.. energizes the particles, into mass.

and it could lead to hydrogen and helium, but i dont think so.. yet i a biased.

-MT
What we have now... today.. is the left over motion of space, which we commonly refer to as time flow.
perhaps we can refer to it as The Relative Velocity Dependant Rate of 4D Two Directional Spatial Motion.

That's dark matter.

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My mistake. I'll read more carefully next time, I hope.

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My link to the website hosting the graphs is not working. Computers drive me crazy. I am so sorry, I am trying to get it fixed.

John

Seems to work now. Post is worthless without the graphs.

Thank you for your interest and I will be responding to the replys soon. My son is graduating from High School and I have to zoom.

Respectfully yours
John

Some quick comments:

- you have no datapoints, nor error bars, on your graphs, snowflakeuniverse. This makes it impossible to do anything with your idea. Further, there's now more data than the points you reference, and (almost?) all folk who work in this field do at least some statistical analyses on the data - will you be doing this in future too?

- the distant SNe work is much more extensive than simply light curves. For example, considerable effort has gone into addressing the question of similarity (are distant Type 1a SNe truly like local ones?), e.g. the appearance of absorption features in the spectra, over time. Second example, time dilation. The distant SNe have light curves that are 'stretched' by just the right amount (within the limits of the data) to be at the distances implied by the lambdaCDM model (plus 'DE'). Have you done the analyses, within your idea, to show that these other aspects of the SNe observations are consistent?

- cosmological models which incorporate DE fit a range of good observational data better than those which don't ... even without the distant SNe data! The point is that the SNe data further constrains the models (the volume in parameter space which is consistent with all data is much smaller), and that there are no data which don't fit!

I look forward to your paper, outlining how your idea is fully consistent with the same set of good observational results that the concordance model is (or, better, that the fit to the data, using your idea, is actually tighter).

As always intresting theroy snowflake.

To be honest I never bought into the 'Standard Candle' theroy myself. It can give us an 'Estimate' of distances, but it's never presented as that, but more as a fact.

My issues with it Are:

For the Type 1a Supernova's to have 'exactly' the same luminosity is an imposibility. White dwarph's are mostly carbon yes, but they will also contain the same proportion of heavier element's as the origional star. Any difference in composition of over .01% would be reflected both in the luminosity of the final nova, and in it's spectography. A white dwarph of pure carbon, accreting put hydrongen from a companion, would have a luminousity much less then one with .02% oxygen and .01% iron in it.

Even if they had the same mass, but with different components, the energy released in a mixed core is larger. The part oxy/iron in my examply would generate more energy and faster when some of the oxygen and iron undo catastophic fusion. This would cause the reaction in the rest of the material to also be accelerated of a pure carbon form.

It could posibly yeild a nova around 1 magnitude difference in luminosity, that would also burn out at a faster rate.

Additionaly the type of matter being accreted onto it that leads to the nova can be just as variable as the composition of the star.

I do realize that they hit a point in critical mass, and that will always be the same, but even just looking at the timing and length of a few type 1a's and thier variences, I just don't see how it could be an accurate representation of distance. A good estimate? Yes, but far from accurate.

In this case I'm more sceptical then the scientist that use this method probably. I'd need to see to see some hard evidence that these type of nova's occur at exactly the same luminosity and rates, with spectral signatures, to put more credence into the distances and luminoisty/red shift they use them to estimate.

I'm not totaly knocking the method either, it's an ingenous idea. But I haven't heard of any study being done on the variability of these nova's due to compositions.

My doubts stem from what happened during the V838 Mon Outbust. When it was first detected, the star was considered just sligtly more massive then Sol at 1.2 solar masses. (et. al. APOD, NASA, hubblesite). For about two years this stayed the same.

Then it became a 4 solar mass star for a while, then a 5-10 mass star...then the supositions about it going red giant in six months was due to swallowing a lage gas giant, or accretion form a companion...

Yet before all this it was rated as a 1.2 solar mass, had a spectral curve that was consitant with that mass of a star, etc...

It's been the contention of a rare few that it's fast evolution into a red giant was due to core composition and not higher mass. We know that stars that have heavier elements can be smaller, have a more stable and longer lasting main sequence, and less variable nature. But the same heavier elements that stabilize fusion during main sequence, would also effect it's evolution, possibly in atypically more rapid manners.

This work made sense to me, and as all information on the star before the even was of a 1.2 sol mass variable, (and there is/was a lot of information this way), this sort of indicated that 1. we know a heck of a lot less about stars then we thought. 2. They evolve in a mouch more varied manner, dependen't on more mass and compostion.

I had to ask myself: if a star that is around 1.2 sol masses can so radically evolve, what would the same compositions cause in other events. Thats when I did a little hunting and found out that type 1a's did not always display quite the same time frames for thier out busrts. Some were a bit shorter and some longer.

So now I sort of question the accuracy of the method. It would seem more honest science if the small variablility in the nature of these were accounted for and we had distance estimates in a low range/high range type presentation.

I could just be nick picking though lol.

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Actually, if you read the literature (and since you are making such sweeping statements about all this, I assume you have read the literature) you will find that there are copious papers trying to figure out if Type Ias from the past are different somehow, or if there is some other reason for the spectra to be different. An exhaustive search has turned up nothing.

While there is still a good deal we don't know about these supernovae, so from theory we can't say how certain we are that they are standard candles, the observational data is pretty good ... when various, well-known factors are taken into account, these objects have a small range of intrinsic magnitudes.

In any case, there are always uncertainties in astronomical measurements; but there is also - in astronomy - the opportunity to find plenty more examples of a particular type of object or event, and then it's statistics to the rescue!

Indeed, if you look at the figure in the link snowflake gives, you'll see how stats are used to estimate the cosmological parameters ... from somewhat noisy data.

Well as I said I'm probably just nick picking.

Law of averages being what it is, the varience of durations of these SNe will average themselfs out in the long run. I still think it could be slightly more accurate if durations were accounted for as well as luminosity, for each event. But I don't have the access to this kind of data to even begin that sort of a study.

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I just saw Hayley's comet, she waved, Said "why you always running in place? Even the man in the moon disappeared, Somewhere in the stratosphere" - Shinedown

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A layman's question about all of this: is there a correlation between the red shift of a SN1a and the luminosity?

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If you mean the observed magnitude, then yes. SN1a are standard candles ... it's through the derived absolute magnitude (worked out from the observed magnitude, the light curve, and so on) that the distance is estimated.

Hi Neried

You mentioned that
“you have no datapoints, nor error bars, on your graphs”

You are correct, in fact the curves for the second graph are exaggerated. The second graph does show that if the data of the supernova relationship were plotted in conventional distance verses time relationships, there is no current “acceleration”.

(If you want to transform the supernova’s graph to that of a standard distance verses time relationship, the proper measure and direction of time on the x axis needs to be established with the beginning of time marking the 0 point on the time axis and the “present” represented at the end of the plot To fix or transform the supernova’s graph to more closely conform to standard distance and time relationship, rotate the supernova groups graph 90 degrees, swapping the x and y axis, then rotate the graph around the new vertical axis 180 degrees.)

Hubble’s constant is constant, at least to a look back time associated with a red shift factor of .1. It is only in the past that there is any evidence of “acceleration”. Therefore the universe is not currently accelerating.

I will be addressing the issue of the similarity of high red shift 1asn’s with local ones in a response to “Bad Astronomer”.

Thank you for your response and interest. I appreciate the feedback.

John

Hi Dgvin

You bring out some good points concerning our seemly blind acceptance of the standard candle assumed for 1asn’s. They are trying to account for variations in the spectral characteristics but trying to account for the variation due to the white dwarf and the donor star will certainly confuse the issue.

When Cepheid Variable stars were first used as a standard candle, the magnitudes for distant Cepheid Variable stars were off by a factor of four. The effects of the accumulated heaver elements within the cores of the stars over time were not properly accounted for. This time we are only looking for a variation in the energy output of 1asn’s of about 25 percent, who knows what unaccounted effect is presently being ignored.

It is the unabashed certainty that the “mainstream” has in just one interpretation of the data that seems so unjustified, particularly since the data is not conforming to our expected understanding of the laws of physics. Adding “dark energy” as a fix has to be understood as at least questionable.

John

Hi Bad Astronomer

You stated

"that there are copious papers trying to figure out if Type Ias from the past are different somehow, or if there is some other reason for the spectra to be different. An exhaustive search has turned up nothing."

Not true.

A few years ago (1999 I think) Riess, Filippenko, Schmidt and Weidong Li, found that distant 1asn have a time to maximum luminosity close to 17 days – 2.5 days less than the rise times of local supernovae. This discovery was based upon a few data points. My theory predicts this kind of shorting of the light curve.

Since that time more data points have been established, and depending upon whom you talk to the above discrepancy has either disappeared or still remains. The variation in the data is enough to allow either interpretation. (I was also told this was so by one of the “experts” at the last American Physical Society meeting this April. Once I find my notes I can give you his name.)

John

Jerry has also made some interesting arguments about this.

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Well, this one should be easy to address .... simply get hold of all the relevant data - in as an unprocessed form as you desire - and do your own analyses. Since the distant SN1a are so critical to your case John, would it be reasonable of any critic of your case (such as myself) to expect that you would have compiled (or are intending to compile) such a dataset? If you consider it a reasonable expectation, where are you up to? If you do not consider it reasonable, would you mind telling us why not?

In any case, how do you feel you could progress with your idea, absent good data?

It's good to see that you are taking the time and trouble to respond to questions etc.

Unfortunately, without any data points or error bars, your simply stating "there is no current “acceleration”" doesn't make it so. Perhaps you could give a table of data, plus the equations for the line(s)? In any case, I feel we need more than a graph without datapoints and a few words to even begin to evaluate your idea.

Finally, when you do plot the data, with error bars, the 'message' will likely be very unclear ... the signal is weak and the noise not. This is quite common in astronomy, and has lead to widespread use of statistical tools for extracting signals (and making quantitative statements about the 'fit' of the model/equation/whatever to the data, signal, noise and all). Are you planning to do statistical analyses of the data?

Hi Nereid

I am perfectly fine with the graphical information that the supernova group posts. The error bars and the various adjustments made to correlate different groups of observers into one graph seem fine to me. Since I have no qualms about the present graphical information presented by the supernova group, there is no need to “do a statistical analysis of the data”, they are doing an outstanding job of doing that right now.

Where I take issue with the group is the interpretation of the data. This is where they have it wrong.


The universe is currently accelerating, based on the graphical information from the supernova group . This is false.

If you want to figure it out for yourself, using only the data given by the supernova group, answer the following questions.

Question 1.
If an object was accelerating but now it is moving at a constant velocity, is it now accelerating?

The answer is obviously no. An object moving at a constant velocity is not accelerating.

Question 2.
What is the current rate of expansion of the universe? Look at the supernovas graph. On their graph “now” is at the origin, and the past is to the right on the x axis. (unconventional graph). Is the rate of expansion “constant” ie, a straight line or linear relationship?

Hubble’s constant describes the rate of expansion. Ho = v/D.

Question 3
Using the graph on the supernova groups data, at a red shift of .01, is Hubble’s constant still observed to be “constant”?

Yes. Hubble’s constant is still constant.

Question 4.
Is an object observed with a red shift of .01 is observed in the past?

Yes

Question 5
If the velocity of an object in the past at a red shift of .01 is moving at the same expansive velocity as it is now, then is the velocity constant from then to now?

Yes.

Question 6
If an object in the past is moving at a constant velocity, and it is moving at the same velocity from that point in the past all the way to the present, is the expansion velocity constant?

Yes.

Question 7
If the expansion velocity is currently constant, how can the universe be described as currently “accelerating”?

So stating that the universe is currently accelerating is wrong, the “acceleration” describes the apparent expansive velocity of galaxies in the past, over a billion years ago.

(Note the universe is actually decelerating, but since the rate of change is so slow and the universe is so old, the rate of expansion is observed to be constant. This was shown on the theoretical graph in which a straight line makes contact with the deceleration curve almost perfectly from “now” to a look back time amounting to about 1/3 the age of the universe. This allows Hubble’s constant to be locally measured to be “constant”. )

Snowflake

The last part of the most recent post...

mmmmm....

Tastes like anthropocentrism. We are just at the exact right place and time that a constantly accelerating model can't be distinguished from a decelerating model...

I, for one, don't like the taste of anthropocentrism. It's a little too pat, and avoids asking further questions with "that's just the way it is" rather than asking "why would it appear that way?"

The assumptions that have lead to the greatest leaps in thought are when we reason as if we were not something special, and I for one think that expansion and cosmology should follow in this vein more than any other science.

The logic presented assumes the hubble constant is constant as part of the argument for the hubble constant being constant. That's a bit of circular reasoning if I've ever seen the like.

Standard candles are different from Hubble redshifts. IF Hubble redshift constant: standard candle (brightness and duration) should agree with redshift. However, for objects closer (less further back in "time" according to Hubble redshift) the delay is longer than it should be, given the redshift. This is where the conjecture about accelerating expansion comes in. One is left with either supernovae are different now than then (taking longer and longer to achieve maximum brightness over time) which implies something special about "now," or redshift is not constant in slope, but accelerating.

The trick is to find out why now looks like now. Finding out a mechanism for expansion and describing its behavior over time might come closer to establishing why the now is not special, rather than putting together special circumstances that by chance lead to what we see now but would not see at any other time.

The idea that the true nature of the universe is hidden by just the right set of circumstances does not wash with me.

Hi Pat Kelley

I think when you are referring to my last post it is about the deceleration looking like a constant rate of expansion. I should have included the link again to the graph so that what I said would make sense.

http://d77591.u25.existhost.com/gpage15.html

The plot is the theoretical rate of expansion based upon principles of general relativity. While there is constant deceleration, locally, the rate of expansion will be measured to be constant, the variation from this linear rate of expansion is very small. This is why Hubble’s constant is locally observed to be a constant. (One of the valid critiques made by Nereid is that I should include the error bars, which would show that the present variation in the data would not reveal the difference in the deceleration and a constant velocity).

The constant rate of expansion is not observed at a red shift of .5, the 1asn’s appear dimmer, and as you noted, further away, no longer mapping to the expected red shift, hence the universe appears to be accelerating (more than a billion years ago, not presently).

There are two solutions possible to have the observation of the high red shift 1a supernovae’s distance correlate to the expected red shifts predicted by theory. Either there is some new form of energy (dark energy) that accelerated the universe, or there is something that causes distant 1asn’s to be dimmer than “local” 1asns.

The fact that such an overwhelming number of the mainstream swallows the idea of some new form of “dark energy” does not wash with me. Dark Energy should be recognized as pure speculation.

Snowflake

Dark Energy, while as yet undefined beyond this vague-sounding term, is still in line with General Relativity (negative pressure in the metric), and does not require that we exist in a special place and time, unlike the decelerating expansion theory which to be viable apparently has to coincide directly with an intercept with the otherwise indistinguishable constant expansion model.


There is a definite difference. A model that incorporates Dark Energy has a component that has observable effects, but no cause as of yet. The proposed decelerating expansion has a cause, but no discernable effect right now. I'd opt for the former, where at least, while I might not know what I'm looking at, I'm more reasonably certain I'm actually looking at something.

Two nitpicks, but very important:

1. The Hubble parameter H is not constant in general. It is defined as (da(t)/dt)/a(t), where a(t) is the scale parameter in the Friedman-Robertson-Walker metric. Only if a(t) is an exponential function will H be constant. Frequently you will see H_0 which indicates the value of the Hubble parameter at the present time.
2. The distance relation v=H*d (more correctly c*(1+z)=H*d) is only true at small distances. At larger distances terms proportional to the second and higher power of d enter and an additional parameter, the acceleration parameter is defined in terms of a(t) and first and second derivatives of a(t).

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Hi PatKelley

You said,
Dark Energy, while as yet undefined beyond this vague-sounding term,
O.K. Since Dark energy is undefined it must therefore be speculative.

Continuing with your quote
is still in line with General Relativity (negative pressure in the metric),
O.K.. But realize this, a model that requires dark energy, means that General Relativity alone in it’s most simple expression, is not sufficient to describe the expansion of spacetime. If it is only gravitational interaction as describe by general relativity, that slows the expansion of spacetime, then the simplest application of general relativity is to have the expansion be described as “flat”, a Perfect balance between expansion and collapse. Of course other models could be proposed but they become more complex.

Continuing with your quote
and does not require that we exist in a special place and time, unlike the decelerating expansion theory which to be viable apparently has to coincide directly with an intercept with the otherwise indistinguishable constant expansion model.

???

When you said the “decelerating expansion theory” are you referring to my uniform expansion model or the Einstein Friedman model which is based upon relativity? Both predict the same deceleration relationships. Gravitational interaction slows the expansion of spacetime. The rates of deceleration for both models would be essentially identical.

You said
has to coincide directly with an intercept with the otherwise indistinguishable constant expansion model.

It seems that I have not conveyed how the “now” observed constant rate of expansion, (as expressed by Ho) is related not only to my model, but to that general relativity. Look at the following graph again.
http://www.uniformexpansion.com/widgets/gen_157.1.gif

This shows the expected rate of expansion, or distance between galaxies, over time, based upon a “flat” universe conforming to the relationships of general relativity. The same graph is predicted in my theory. The constantly sloped line defines the velocity of the expansion, or Ho. From our perspective of “now” looking to the past, the difference between the straight line, and the true decelerating curve is virtually the same to a look back distance of 1/3 the age of the universe.

When you said,
and does not require that we exist in a special place and time
And that is where my model differs from, and yet is compatible with, General Relativity.

You exist at a special moment in history, that no one else can have. Most of the math in my model requires using this historical dimension of time that demarcates a point’s location relative to the beginning of time.

Snowflake

Hi Celestial Mechanic

Thank you for stating some of the basics.

You are right to say that

The Hubble parameter H is not constant in general.

You then said.
Frequently you will see H_0 which indicates the value of the Hubble parameter at the present time

Which is why I used Ho in the graphs and this text.


You also said
The distance relation v=H*d (more correctly c*(1+z)=H*d) is only true at small distances.

I know you mean small on a cosmological scale of things. But it is not that small.

If we look back to about 1/3 the age of the universe, or to be more conservative, consider looking back to 1/10 the age of the universe, the rate of expansion is essentially constant. So from our location in time to a look back of 1/10 x 15 = 1.5 billion light years away, the rate of expansion is constant.

So for the last billion years, the rate of expansion has been and is constant, it cannot be presently accelerating.

The “acceleration” is only observed in the past, ie at red shifts factors greater than .1


Snowflake.

I like to think I am a decent communicator, however it appears that I did not establish the correct terminology, as you have rephrased it.

The mechanism of the described "Dark Energy" is undefined. The effect is not. Many of the proposed mechanisms are speculative. The effect is not. Dark Energy is similar to gravity in this respect; many approaches to the cause or mechanism that are speculative; but one would not say that because of this the effect of gravity is speculative.
General Relativity is more than E=mc^2. It also encompasses spacetime metrics for defining curvature; one solution of which includes a "negative pressure." This negative pressure originally was thought to be exotic or a quirk of the model; however it appears that Dark Energy fits the negative pressure metric, which doesn't violate General Relativity.
Not really. Negative pressure is valid under the metric, without any extraneous addition of factors.
What you illustrate with your graph is a model in which a uniform expansion is indistinguishable from a decelerating expansion; a null-set for defining differences between models. Rather than a special circumstance, you are instead saying at no time could we distinguish between the models?
So there is no way of determining whether either model is correct, in that your model has no observational differences from the current model?
There is a problem in that there is the spacetime metric and its transoformations which preclude simultaneity, so a point's location in time is relative. Two people could "see" the same thing, and each think they were unique in observing it in their way at their time; but there is no real way to determine between the two when the event occurred without more information. Two people from their own perspectives could have left the earth six minutes ago; however, from the earth's point of view one left six minutes ago, one more than sixty, depending upon the reference frame.

Hmm, it may be a good idea, snowflakeuniverse, to read up on GR.

For example, GR itself is agnostic about what forms 'mass-energy' can take, and as PatKelley pointed out, 'negative pressure in the metric' is pure GR. That you, or PatKelley, or anyone else chooses to call the 'thing' we conclude from good observations that is consistent with 'negative pressure in the [GR] metric' Dark Energy, is nothing but a convention.

Further, GR itself is agnostic over complexity and simplicity - a million different kinds of mass-energy or one (or even none!) are all consistent with GR.

What you are pointing out, it seems to me, is limitations or weaknesses of certain cosmological models based on GR, not what GR needs, requires, implies, or is in love with.

I will get back to this thread later, but just to telegraph ... there are, IMHO, several confusions and misunderstandings in your recent posts; they relate partly to the cosmological models you are aiming to critique, and partly to what the SNIa data itself actually 'says'.

{l8ter}

[Edit: I see that PatKelley and I have written posts, which 'crossed in the mail' Good to see that we are saying the same thing, more or less =D> ]