How well has Cosmic Inflation been verified?

This was a question I asked myself...................
https://www.forbes.com/sites/starts...-cosmic-inflation-been-verified/#14aa43941d07

Pertinent extracts follow:

Q: To what margin of error or what level of statistical significance would you say you say inflation has been verified?
A: The short answer is "better than most people think." The long answer is even more compelling.

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The redshift-distance relationship for distant galaxies. The points that don't fall exactly on the line owe the slight mismatch to the differences in peculiar velocities, which offer only slight deviations from the overall observed expansion. The original data from Edwin Hubble, first used to show the Universe was expanding, all fit in the small red box at the lower-left.

ROBERT KIRSHNER, PNAS, 101, 1, 8-13 (2004)

The Big Bang is an incredibly successful theory. It began from just two simple starting points, and made an extrapolation from there. First, it insisted that the Universe be consistent with General Relativity, and that is the theory of gravity that we should use as our framework for building any realistic model of the Universe. Second, it demanded that we take seriously the astronomical observations that galaxies, on average, appear to be receding from us with speeds that are in direct proportion to their distance from us.
more at link.....
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The following points as detailed in the article and conducive with GR, tells us...
[1]The Universe/space/time being filled with matter/energy, means that it must be dynamic. [A fact that led to Einstein's biggest blunder, in his own words]
[2] It must expand or contract.
[3] The redshift/distant relationship of galaxies, confirms expansion.
[4] While the matter/energy content remain the same, as a result of expansion, the universe/space/time is getting less dense.
[5] In this growing less dense universe, gravity over time, acts by attracting the matter into ever increasing lumps, creating our galaxies.
[6] Light from distant galaxies undergoes redshift, hence less energetic and a drop in temperature...the CMBR at 2.73 K.
[7] Mentally reversing this expansion of the universe/space/time, sees pressures and temperatures increase the further back we go, and a more uniform state, as per the following illustration...

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After the Big Bang, the Universe was almost perfectly uniform, and full of matter, energy and radiation in a rapidly expanding state. The Universe's evolution at all times is determined by the energy density of what's inside it. If it's expanding and cooling today, however, it must have been denser and hotter in the distant past.

[8] The increase in temperatures and densities, eventually lead to atomic fusion the further we go back.
[9] This leads to the abundance of the lighter elements.
[10] The formation of atoms follows as temperatures reach the required threshold.
[11]The Universe becomes opaque with radiation/light being allowed unimpeded movement and continuing redshifting until reaching the current 2.73K we observe today.
[12] Stars form under gravity, forging the heavier elements.

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A visual history of the expanding Universe includes the hot, dense state known as the Big Bang and the growth and formation of structure subsequently. The full suite of data, including the observations of the light elements and the cosmic microwave background, leaves only the Big Bang as a valid explanation for all we see. As the Universe expands, it also cools, enabling ions, neutral atoms, and eventually molecules, gas clouds, stars, and finally galaxies to form.



The above are the reasons why the BB is still the most overwhelmingly supported model of universal evolution.
But that doesn't mean it's perfect by any means.
The imperfections summaries follows in chapter 2!
continued:

 

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As per the article, the following are examples of imperfections and anomalies in the BB model of universal evolution.....

[1] We observe the universe to be isotropic and homogeneous at all distances, in all directions, when viewed at larger scales. This is hard to fathom in a universe that has been expanding for 13.83 billion years, and beggars the question, how such uniformity could be obtained.

[2] The absence of left over remnants of that early time and magnetic monopoles.

[3] WMAP has observed that the universe is spatially flat with no observed curvature, noting the BB at those early hot, dense times, had no reasons, means or mechanism to produce such flatness.

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If the Universe had just a slightly higher density (red), it would have recollapsed already; if it had just a slightly lower density, it would have expanded much faster and become much larger. The Big Bang, on its own, offers no explanation as to why the initial expansion rate at the moment of the Universe's birth balances the total energy density so perfectly, leaving no room for spatial curvature at all. Our Universe appears perfectly spatially flat.

NED WRIGHT'S COSMOLOGY TUTORIAL

[4] The BB and current laws of physics, including GR, fail to tell us anything back further then t +10-43 seconds.

This is where Inflation comes in and the reasons why it was necessary......

In short and as summed up by the article Inflation tells us that the BB was not precisely the beginning, and that the Inflation is an inherent property of spacetime itself, and a very large energy density.
This was the cause and reason as to why the early universe underwent a rapid expansion, driving the matter apart and initiating the flatness that we observe.
This is best explained in the diagram from the article and explanation that follows.....

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In the top panel, our modern Universe has the same properties (including temperature) everywhere because they originated from a region possessing the same properties. In the middle panel, the space that could have had any arbitrary curvature is inflated to the point where we cannot observe any curvature today, solving the flatness problem. And in the bottom panel, pre-existing high-energy relics are inflated away, providing a solution to the high-energy relic problem. This is how inflation solves the three great puzzles that the Big Bang cannot account for on its own.

E. SIEGEL / BEYOND THE GALAXY

This as Alan Guth realized, explained all the anomalies that the BB missed, while still adhering to the four pillars of cosmology that the BB adequately explained.

Inflation also made predictions which are listed as follows.....
[1] A maximum temperature that can be achieved by the universe, post Inflationary period.
[2]Fluctuations that light could never traverse since the BB do exist.
[3] Quantum/Inflation fluctuations producing the seeds of density fluctuations, more fully explained in the article.
[4] The fluctuations need to be scale invariant.
[5] A flat universe with margins of error in the .01% range
[6] Primordial Gravitational waves.

The first four have been confirmed, and the fifth to within 0.4%, with only the sixth not as yet validated.

The article concludes thus.....................

"Inflation has literally met every threshold that science demands, with clever new tests becoming possible with improved observations and instrumentation. Whenever the data has been capable of being collected, inflation's predictions have been verified. Although it's perhaps more palatable and fashionable to be a contrarian, inflation is the leading theory for the best reason of all: it works. If we ever make a critical observation that disagrees with inflation, perhaps that will be the harbinger of an even more revolutionary theory of how it all began."

 

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The author of the article and his credentials are as follows......
https://www.forbes.com/sites/ethansiegel/#61beeb3b683e

Ethan Siegel
I am a Ph.D. astrophysicist, author, and science communicator, who professes physics and astronomy at various colleges. I have won numerous awards for science writing since 2008 for my blog, Starts With A Bang, including the award for best science blog by the Institute of Physics.

 

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To Alex:
I'm not sure how this reflects on the different aspects of inflation, but it is a good article and explained well by Ethan.

 

First I thank you for putting in so much effort to try and present a picture that we can look at.
Do you want me to address each point and show where they have gone wrong ...we could take it point by point over many weeks.
Rather than start addressing each point you may be able to answer what has be running around in my head today and touched on in your fine post...actually it does not seem to be here..maybe the other post??? But I am sure I saw it..anyways..whatever I imagined said GR dictates the universe must act dynamically such that it must expand or contract...I wonder why must GR tell it so given at one point it gave the opposite conclusion ..because of CC of course...but even with out it how does GR hint at what the universe must do...that's what I would like to understand...I mean what did they do with the equations , the inputs etc to come up with such a result...I am no math master so I wonder how someone sat down with the equations and input what, I mean what would you put in for a start...so much in a universe...it's mass density and volume but where could you get those numbers.

An article can make claims just like anyone so let me consider the claims in this one...
First..the claim that inflation has met every threshold that science demands is certainly not the impression I ha e formed by my casual reading over years, maybe I miss the good stuff that has the author claiming science is satisfied with its demands being answered but it's funny I have not found something that supports that claim and although it has been years since I did do a lot of reading on the subject the first article I turned up recently, that Forbes article, certainly did not mention anywhere that science was happy in fact the author of that article said the very opposite saying that all inflation was good for was a proliferation of papers.
In any event the claim made in the article you mentioned has no back up ... and it says with clever new tests becoming possible etc..now that sounds like so much BS...how can they test etc inflation..in any event why when the theory was first presented did someone no ask..any tests? Any experiments? Any observations?
And...it works??? Of course it bloody works it was reverse engineered how could it not work for goodness sake.
I submit that to accept inflation is no better than accepting what the pope tells you to believe...we critise theists for travelling on faith alone but is acceptance of inflation any better...
I did not dream it...earlier re GR..here is what I was thinking about.

I don't think it went that way in fact...but I will look into what I may claim before I claim it if indeed I bother to make the claim that I have decided not to make..I am interested in how you could sit down with the equations of GR and build a universe and certainly what your inputs could be...the only way to get anywhere is to learn how they went through the process...maybe there is a YouTube video.
Alex

 

Actually, there are textbooks and, as paddo showed, research articles.

Of course you could always sit down and do what many of us have done - learn the differential geometry as it relates to GR

 

Thanks for the good advice. Is there a text book you could suggest and do you think one could learn this without being enrolled in a course?

I think my math would let me down and frankly I think I would have to start again at a High School level. I have read a great deal of things on the net but it is perhaps not useful as I end up with more questions that clearly needs a much higher level of understanding of the subject than I am likely to achieve...I did read up on the geometry but only have a hint of what is involved.
Why I mentioned a YouTube video is I did see one that linked the work of Galileo, Newton to how Einstein approached gravity and although simplistic it was an eye openner for me.
Probably the train has left the station for me really as my old brain is not as good as it once was and in any event my input and replies to Paddo as I pointed out some time back is more in the nature of Devils advocate to give opportunity for him to address matters ...further although I come over very critical in truth much of it is an act, I respect the idea of scientific models and what is needed for an established model to be replaced...
Anyways now that you are here what is your view on inflation and say the critism in the earlier Forbes article?
Thank you for your suggestion and if you can think of a book that may help please let me know.
Alex

 

I have started



Alex

 

There are any videos after the one above...but it's going to take all morning to learn all this.
Alex

 

Up to here


Alex

 

First note Alex that being a novice, my knowledge of GR and the mathematical equations involved, is, well pretty basic.

From historical accounts, [which I have no reason to disbelieve] when Einstein first completed his 10 year work on GR, he noticed that the equations, predicted a dynamic universe, one way or the other [collapsing/expanding] The prevailing evidence and belief at the time was that the universe was static. So Albert not being perfect and going along with the established belief, based on the available evidence, tweaked the CC, [which was always a part of GR as far as I know from memory] to reflect his static universe belief. Later Hubble discovered the redshift of distant galaxies in relationship to distance and Einstein saw his tweaking as his greatest blunder.
I found this, which at this time I have not fully read and will do today.
http://www.scholarpedia.org/article/Cosmological_constant

 

I am unable to actually find anything confirming that the CC was always a part of GR Alex, so maybe I imagined it? I put it down to being an old bastard!

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Here, this is interesting....
http://www.astro.ucla.edu/~wright/cosmo_constant.html
Einstein's Greatest Blunder
However, there is a basic flaw in this Einstein static model: it is unstable - like a pencil balanced on its point. For imagine that the Universe grew slightly: say by 1 part per million in size. Then the vacuum energy density stays the same, but the matter energy density goes down by 3 parts per million. This gives a net negative gravitational acceleration, which makes the Universe grow even more! If instead the Universe shrank slightly, one gets a net positive gravitational acceleration, which makes it shrink more! Any small deviation gets magnified, and the model is fundamentally flawed.

In addition to this flaw of instability, the static model's premise of a static Universe was shown by Hubble to be incorrect. This led Einstein to refer to the cosmological constant as his greatest blunder, and to drop it from his equations. But it still exists as a possibility -- a coefficient that should be determined from observations or fundamental theory.
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I'm still rather confident that mathematically speaking the CC was always a part of GR, and it just needed tweaking, to align with the static model [which apparently wasn't very static

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]
Can someone knowledgable in GR confirm or deny this?

 

Best of luck!!!

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Yes I know all this in general but what I wonder is what inputs did he use..ok you have your equation I expect but without an input for say the mass of the galaxy or the local group..whatever... like what was his step by step approach...what observations did he use?

So far my understanding of the math is not much more than useless but I imagine that at some point you have your equation and you say...let's test this on something...mmm works on the cat let's see how it goes on the Solar System...that went well..let's try the local group of galaxies...Do you see what I mean?.. I have been looking at the YouTube geometry stuff and I can follow it to a limited degree..but it is geometry after all..it sets out how to make a curve etc in 2 d then 3d and we can include time but I have not found how the geometry dictates anything..it is geometry after all.

I don't know my lack of knowledge gets me so frustrated...you should watch the videos I linked on the geometry..the key is just let it flow and not to say what the hell is he talking about and you will get the general idea of what is going on I think.

Maybe it just a math thing but it would be disappointing if they had the equations and did not input the mass of the galaxy..that sort of thing.
Alex

 

It is not that bad.

Once I would dwell on something I did not understand but now I will not let myself get hung up and just keep going and although I miss so much I at least know what the game is..don't know all the rules is all.

In any event at our age pushing the old brain can't hurt ...I am trying to learn biology...how protons run energy units inside a cell and how they construct a water molecule...I got my hands on a small microscope and probably will buy a decent one...with a camera...but there is so much to it..but I now know all the bits of a microscope, how to calibrate, various procedures, what to buy what not to buy...the little one I have has a camera..this one only cost $70 can you believe that..and it must have plastic lens but the image is not bad certainly way past what I expected for the money..you should get one..and a telescope ...I plan going for a $2000 one and it is acceptable according to the Health Dept to count worm eggs in the horse shit just like the vet would do..maybe I could ask around and get work counting worm eggs...mmm need a lab coat and a clip board.
Alex

 

Yep, certainly understood.

I can't add much more Alex, then to suggest it was similar in the finding of Neptune, because the maths predicted it beyond Uranus, while never had been sited, at that time.
With GR, and the fact that gravity is always attractive, meant a dynamic universe [eventual collapse] which contradicted the thoughts of that period.

Yeah but your 4 years younger then me!

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Agreed, but you still have that 4 years advantage on me!

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And I have a religious Mrs that sometimes distracts me from the awesome nature of cosomology and astronomy.

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A shame that we don't have too many members interested in the subject. Dave and Janus are probably two that could add something more concrete, particularly about my thought that the CC was always a part of GR and it was simply its "value" that needed to be tweaked.
Oh, and James of course is probably capable of adding some knowledge!

 

But you must, your are one of the few people I trust.

Well my suspicion is he did not use real observations...his wife gave it away with a throw away comment that gave him up..that's what wives do..she said that he worked out the universe on the back of an envelope...that needs to be checked..but I think they were with Hubble chatting about universes as one does when looking at telescopes...I wish I still had my library ( most extensive and lost in the fire of 2002) as I could confirm the facts that I can't recall.

I maintain that the claim that there exists a force of attraction has never been backed up...folk just say this is attracted to that but there never has been anything to show that such a force exists...and it is when one tries to show how such a force could work that one is forced to conclude there is indeed likely beyond rebuke that there is no such force.
You may notice that GR does not use any force a clear indication that it's inventor perhaps had also realised there can be no such force and certainly produced a happy result without including an unestablished force.
The Cassimer effect clearly shows the plates are pushed together without any force of attraction.
Alex