Rumors of inflationary theory's demise premature, researchers say

May 11, 2017 by Amy Adams
Professor Andrei Linde is among the physicists responding to a recent media story taking aim at inflationary theory. Credit: L.A. Cicero

From the earliest human civilizations, people have looked to the heavens and pondered the origins of the stars and constellations above. Once, those stories involved gods and magical beings. Now, there's science, and a large research enterprise focused on understanding how the universe came to be.

Squarely in the center of this research enterprise is what's known as inflationary . It argues that the was born out of an unstable, energetic vacuum-like state then expanded dramatically, spinning off entire galaxies produced by quantum fluctuations. This theory was proposed in 1980 by Alan Guth, presently at MIT. A year later, this theory was improved and extended by Andrei Linde, Stanford professor of physics, who has spent a lifetime modifying and updating it as new data emerged.

During the last 35 years, many predictions of inflationary theory have been verified by theorists and confirmed by cosmological observations. Gradually, this theory became a generally accepted description of the origin of the universe. So imagine Linde's surprise when Scientific American published a story in February by Paul Steinhardt, a professor of physics at Princeton, and his colleagues declaring its demise.

In response, Linde and Guth, along with their colleagues David Kaiser from MIT and Yasunori Nomura from the University of California, Berkeley, have written a letter defending the inflationary theory, published in Scientific American May 10. It was signed by 33 academics who read like a Who's Who of theoretical physicists, including Stephen Hawking of Cambridge University. In it, they take aim at the primary argument in the story: that inflationary theory isn't really a scientific theory because it doesn't predict anything and therefore can't be tested.

"As the work of several major, international collaborations has made clear, inflation is not only testable but it has been subjected to a significant number of tests and so far has passed every one," the group wrote.

A flat universe

As one example, the inflationary model had predicted that if the universe is ever expanding, it would now be flat rather than open or closed. (Imagine a balloon growing infinitely large. Eventually its surface would appear completely flat.) A would be represented by a variable called Omega that is equal to 1, "Well, plus or minus a little bit because of quantum uncertainty," Linde said.

In fact, in the mid-'90s many astrophysicists believed that the universe was actually not flat, with an Omega closer to about 0.3. "That would be a disaster for inflation," Linde said. He then tried to find the flaw in his own theory. However, all attempts to construct a model of inflation with Omega equal 0.3 were unsuccessful; the proposed modifications of inflationary theory were extremely complicated and unnatural, and most of them simply did not work. Fortunately, in 1998, a series of revealed the existence of dark energy. It turned out that the energy of a vacuum is not zero, as previously thought, and Omega was restored to 1.

"If inflationary theory can't predict anything, why could it appear to be dead when a prediction turned out not to be true?" Linde asked. And how could it be restored by that validated the prediction?

A tense time

A similarly dramatic situation emerged five years ago, when rumors circulated about a fairly technical issue that's known as the Gaussianity of inflationary perturbations. The main thing to know about Gaussianity is that the discovery of a large non-Gaussianity of a specific type would rule out 99.9% of the existing inflationary models.

In 2012 and winter 2013, there were persistent rumors that this non-Gaussianity would soon to be reported by the Planck satellite, and in fact preliminary data by the WMAP satellite indicated a possibility of a very large non-Gaussianity. If that had turned out to be true, it could be a crucial blow to the inflationary theory.

However, the Planck data revealed no traces of non-Gaussianity. The very last sentence of the Planck paper describing that data read, "With these results, the paradigm of standard single-field slow-roll inflation has survived its most stringent tests to-date."

This and many other successful predictions of inflationary theory are undeniable facts, Linde said. "If we trust the arguments made in the Scientific American story, all successful predictions of inflationary cosmology are the result of pure luck, like winning the lottery," Linde said. "One can do that once, twice, but not this many times. That is why so many leaders of modern physics signed our letter."

Linde added that the letters section of a popular magazine is not normally where scientific debate plays out. "A long time ago, when I was young and naive, I thought that things like that are impossible in science," he said. Now, he just hopes people see that the opinions in the story are not shared by many of the biggest names in theoretical physics and observational cosmology.

Linde added that he worries about the younger generation of scientists getting the wrong impression from this story. "I don't want them to read this article and think that they are spending their time on inflationary theory in vain. But the enthusiastic support that we are receiving makes us optimistic that this is not going to happen," he said.

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RNP
5 / 5 (6) May 11, 2017
Clearly, those on this site claiming that inflation is DISPROVED by Prof. Steinhardt's ideas are inflating their significance (at least in the opinion of 33 top research scientists).
RealityCheck
1 / 5 (5) May 11, 2017
@RNP.

Sad to see such self-deluded, confirmation-biased 'religious adherence', to OBVIOUSLY UNTENABLE hypotheses/interpretations of observations/data.

It's even sadder to see it in so-called 'respected' scientist 'professionals'.

It's like you/they never looked at, at let alone 'objectively processed', all the obvious flaws in BB/Inflation etc assumptions built into all Inflation/Expansion 'work' for DECADES now.

I long pointed out all the obvious flaws in 'Cosmic Distance Ladder' methodologies; circuitously relying on ad hoc interpretations; and then more 'work' based on such 'interpretations'....until BB/Inflation etc became a RELIGIOUS 'belief' not SCIENTIFIC 'fact'.

OLD Supernovae/CMB 'work' NOW being reviewed/proven UNRELIABLE/SIMPLISTIC by NEW astro/cosmo discovery/review.

And ALL 'exotic' DARK ENERGY and DARK MATTER are ad hoc 'beliefs' by 'confirmation biased' RELIGIOUS ADHERENTS trying to 'rescue' BB etc.

It's just painful to watch now.

Rethink it all!
TimLong2001
1 / 5 (6) May 11, 2017
The required 13.7 billion year age of the universe is blatantly foolish -- especially with the greater telescopic power we now have showing larger and larger cosmological structures at greater and greater scales. The pair formation of "Threshold Gammarays," in addition to satisfying supersymmetry, is sufficient to populate the observable universe given enough time. (Photons are bosons, BTW.) Smaller scales would supply charged particles for the virtual particle field, and constructive interference increases the energy of electromagnetic radiation to threshold. CMBR, which varies slightly from place to place, might be the local average interference frequency of all radiation in the observed volume of space.
Da Schneib
5 / 5 (6) May 11, 2017
Well done; and good job Andrei Linde doing it, he's the best one to say it. The evidence is clear in the CMBH, and it needs to be clear to everyone that the Planck observatory has clinched it.

It's clear that there's a pretty good set of reasons why ΛCDM is the "Standard Model of Cosmology." And no good reasons why it's not.
Da Schneib
5 / 5 (5) May 11, 2017
@RC whines that @RNP actually posted the link to the public access article? Ohe noes teh evul astronomipycisksists posted teh reul data, how hineous? Teh reul datumxs is teh standerd paradigum liez teht benz teh mindz of teh populice?

Geez c'mon @RC. I mean, really. How transparent can you be?
RealityCheck
1 / 5 (5) May 12, 2017
@Da Schneib.
@RC whines that @RNP actually posted the link to the public access article?
Why strawman like that, DS? Are you that afraid of facing the reality instead of just 'believing' what you want to believe about posts/persons/science? Didn't you learn the lesson from the Bicep2 'uncritical beliefs' fiasco?
Ohe noes teh evul astronomipycisksists posted teh reul data, how hineous? Teh reul datumxs is teh standerd paradigum liez teht benz teh mindz of teh populice?
Is that you speaking objectively on the 'science', DS? Or just more of your tactics of avoiding facing reality/science as is NOW being discovered by mainstream itself?
Geez c'mon @RC. I mean, really. How transparent can you be?
Not as transparent as your above totally transparent 'preference' that you'd rather keep 'uncritically believing' your 'preferred myths' than get up to date with the reality and the science as is being discovered NOW by mainstream itself. You betray intellect/science, DS.
Seeker2
5 / 5 (6) May 12, 2017
@RC
And ALL 'exotic' DARK ENERGY and DARK MATTER are ad hoc 'beliefs' by 'confirmation biased' RELIGIOUS ADHERENTS trying to 'rescue' BB etc.
Still confusing beliefs with hypotheses?
Seeker2
5 / 5 (6) May 12, 2017
@RC
...get up to date with the reality and the science as is being discovered NOW by mainstream itself.
You mean as described in this article?
RNP
5 / 5 (5) May 12, 2017
@RealityCheck
Sad to see such self-deluded, confirmation-biased 'religious adherence', to OBVIOUSLY UNTENABLE hypotheses/interpretations of observations/data.

It's even sadder to see it in so-called 'respected' scientist 'professionals'.

It's like you/they never looked at, at let alone 'objectively processed', all the obvious flaws in BB/Inflation etc assumptions built into all Inflation/Expansion 'work'.

As usual you provide nothing but unsubstantiated claims and insults. Why don't you adhere to the principle that you always extol of using posts for *scientific* discussion?

Just denigrating authors and saying "I am right and you/they do not understand" is NOT scientific.

So let's try a little scientific discourse for once, shall we?

Leaving aside all your silly other claims, why don't you explain *exactly* how the ideas in the article linked above are wrong. Then I, or somebody else that understands the subject, can give sensible responses to your claim.
Merrit
4.8 / 5 (4) May 12, 2017
It is currently our best model whether it is correct or not. For instance, the big bang could have simply been a local event rather than involving the entire universe. The fabric of space time could have only been inflated in the local area. There could very well be big bang events occurring constantly throughout the universe, but far enough apart to have no effect on eachother. We can only observe our observable universe, which could very well be insignificant compared to the entire universe. Like the size of a grain of sand compared to our solar system for example.
RealityCheck
1 / 5 (3) May 13, 2017
@Seeker2.
@RC
And ALL 'exotic' DARK ENERGY and DARK MATTER are ad hoc 'beliefs' by 'confirmation biased' RELIGIOUS ADHERENTS trying to 'rescue' BB etc.
Still confusing beliefs with hypotheses?
Who is? Not me. I point out that your beliefs based 'interpretations' of data, and any further speculative fantasies flowing from same, are NOT "hypotheses" in the science sense, but just fantasies and myths 'beliefs'. Just like some 'mathematical' abstractions are not 'scientific realities', but rather just 'unreal' mathematical 'artifacts', ie mathematical 'fantasies'. How long will it take for that crucial scientific distinction to sink in for you, Seeker2?
RealityCheck
1 / 5 (3) May 13, 2017
@RNP.
Sad to see such self-deluded, confirmation-biased 'religious adherence', to OBVIOUSLY UNTENABLE hypotheses/interpretations of observations/data.

It's even sadder to see it in so-called 'respected' scientist 'professionals'.

It's like you/they never looked at, let alone 'objectively processed', all the obvious flaws in BB/Inflation etc assumptions built into all Inflation/Expansion 'work'.
As usual you provide nothing.... So let's try a little scientific discourse for once, shall we?
Been there, tried that, for years now! You/gang just trolled, attacked, derided, bot-voted etc...in short, you did EVERYTHING TO PREVENT objective science discourse of ideas/issues! You/gang just wanted to 'bash cranks'. Well, we all know what your/gang 'attitude' and 'method' led to, don't we, RNP? Yep, your/gang's Bicep2 fiasco, 'believing' uncritically due to YOUR CONFIRMATION BIAS as to 'source/claims'.

Now BB, Inflation etc proponents are self-correcting. Stop whining. :)
Da Schneib
5 / 5 (3) May 13, 2017
@RC, stop making up excuses for your behavior.

All you have is a bunch of FUD. You won't engage on technical issues with people who know what the technical issues are. It doesn't matter who did what, particularly not after you have repeatedly refused to engage on the technical issues; it matters if you have cogent technical arguments. And you never do. If you bring kak like this when you are challenged on technical issues, it's clear evidence you are not competent to argue them.

And if you're not competent on the technicalities, then arguing them is trolling. Simple as that.
RealityCheck
1 / 5 (3) May 13, 2017
@Da Schneib.
@RC, stop making up excuses for your behavior.

All you have is a bunch of FUD. You won't engage on technical issues with people who know what the technical issues are. It doesn't matter who did what, particularly not after you have repeatedly refused to engage on the technical issues; it matters if you have cogent technical arguments. And you never do. If you bring kak like this when you are challenged on technical issues, it's clear evidence you are not competent to argue them.

And if you're not competent on the technicalities, then arguing them is trolling. Simple as that.
For someone who is so certain and insulting, it is a pity you are not up to date with the science facts/insights being discovered/reviewed now by mainstream which confirm ME correct on many fronts...while you/gang are left 'believing' all sorts of increasingly outdated/ invalidated crap.....just because you think you can 'parrot' and 'technically discuss' same...while being wrong.
RNP
5 / 5 (3) May 13, 2017
@RealityCheck
Been there, tried that...

This is a sequence of blatant lies. You have never engaged in scientific discussion with me. In fact, you seem incapable of such a thing. I have also never "bot-voted" anything. I vote on the merits of posts, not their author, as you well know (you have on more than one occasion thanked me for voting you a 5).

Your response to my request for a scientific discussion of the topic is therefore not only pure evasion, it is also testament to your profound dishonesty.

Regarding BICEP: I did not visit this site at the time, but having read the 2014 paper, I knew that the authors themselves were uncertain of the result as, in the abstract, they clearly identified a problem. (See https://journals....241101). This turned out to be an actual flaw (not one of your imaginary "four fatal flaws").

Having reminded people of how bad a troll you are, I will again start ignoring your deceitful nonsense.
RNP
5 / 5 (3) May 13, 2017
Sorry, the link above does not function.

The BICEP paper, the abstract of which says:
" However, these models are not sufficiently constrained by external public data to exclude the possibility of dust emission bright enough to explain the entire excess signal"

(this turned out to be the actual probem) can be found here: https://journals....2.241101
Dingbone
May 13, 2017
This comment has been removed by a moderator.
Dingbone
May 13, 2017
This comment has been removed by a moderator.
RealityCheck
1 / 5 (3) May 13, 2017
@RNP.

Read that in fuller context, RNP. That little snippet was swamped by their continuing claims to have observed evidence for primordial gravitational waves. They stood by their 'claims' for many months, including in subsequent press conferences. If they really had been objective they would not have made those claims at all at that time and continued them subsequently. That 'disclaimer' snippet was just window dressing to cover serious flaws and untenable claims which were obvious to any objective observer. Ask yourself: why make such an announcement/claim at all IF they KNEW that the dust data may scupper their claims within months? Why would a truly objective 'scientific' exercise not WAIT a few months for better data they KNEW was forthcoming? The old 'publish -or-perish' and other personal/mercenary 'imperatives' got the better of that 'team'. It was obvious to all objective observers, regardless of the excuses from those who 'just believed' due to confirmation bias.

cont
RealityCheck
1 / 5 (3) May 13, 2017
cont... @RNP.

As for your bot-voting/sabotage 'by proxy', it is plain for all to see, RNP. You have long overtly/tacitly condoned the atrocious behavior of that bot-voting gang, and even congratulated them; for skewing the ratings metrics against those whom you would insult, attack and/or ignore when 'convenient' for you. Ask yourself, RNP: have you ever condemned their behavior, RNP? Especially when they sabotaged and trolled and bot-voted against me even though I was correct all along? No, you just went along and pretended to be better than them (it is sufficient that good men/women to do nothing for evil/trolls to flourish) while also attacking me even though I had been pointing many things out for your/their benefit for years: while they just merrily sabotaged and/or ignored; and now have the gall to claim I never tried! Well, too late now; I've not time/inclination to go over years' worth of reminders/insights lost on trolls ("Pearls before swine" comes to mind).

Dingbone
May 13, 2017
This comment has been removed by a moderator.
RealityCheck
1 / 5 (3) May 14, 2017
@RNP.

Do you even realize that bot-voting '1' (in concert with the other bot-voting troll UI) for my above posts, makes a mockery of your claim to ignore me? Do you even realize that your bot-voting again proves my point: that you bot-vote based on your own preconceived biases rather than having regard to what is pointed out in response to your continuing confirmation-biased 'takes' on the matters in question? It is not surprising that you are so irretrievably biased, given that whole 'teams' of so-called 'scientists' (eg, Bicep2 fiasco) can also succumb to that science-betraying 'malaise' which is all too infectious in 'incestuous circles' arising/created from/by 'herd-mentality' type 'hacks' exploiting 'uncritical belief' tendencies in people like yourself/that 'gang' of insensible, science-betraying, bot-voting, ignoramuses and hypocrites who delude themselves thay are being at all 'scientific' or 'objective' even as they PROVE themselves trolls, like you just did. Sad.
Dingbone
May 14, 2017
This comment has been removed by a moderator.
Dingbone
May 14, 2017
This comment has been removed by a moderator.
Dingbone
May 14, 2017
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