The Cosmic Inflation Controversy

I have sometimes defended the theory of cosmic inflation in these forums — it explains things like the formation of galaxies and the ‘isotropic’ (uniform whichever way you look) distribution of matter in the universe pretty neatly. It also has the endorsement of leading scientific authorities such as Steven Weinberg and Stephen Hawking. But there have always been problems with inflation, the main one being that we can’t really test whether it happened or not. In this it is different from the Big Bang itself:

The beautiful, cosmic microwave background and the light-element abundances tell you, ‘This is it.’

Now, a ‘stinging critique’ of inflation has been published in Scientific American. You can read a short, social-media-friendly ‘article about the article’ here.

The authors of the critique, one of whom shares the credit for formulating the inflation hypothesis, charge that it makes no testable predictions and is unfalsifiable.

In response, 33 scientists including Hawking, Weinberg and two scientists who share the credit for thinking up inflation with the author of the critique, have replied in a letter to SA, defending inflation from the charges levelled against it but ultimately acknowledging that nature itself must be the final judge of all theories:

Empirical science is alive and well!

This, I believe, is how progress in human understanding is achieved.

By the way, if anyone wants to drop by and inform us that the Big Bang is all nonsense, I urge them to reconsider. There are plenty of threads on that subject already, including this one, where I and others discuss the subject from many different angles.

Thanks in advance.

a reply to: Astyanax

Scientist arguing over which speculation is the best way to interpret the data! Say it isn't so!

a reply to: dfnj2015

It isn’t so.

Not interested in cosmic inflation, or the linked articles? There are plenty of other threads on Above Top Secret.

a reply to: Astyanax

I'm a believer in a cyclical universe (expansion->contraction->expansion->contraction and so on), but there's always been one niggling little problem with the expansion/inflation side of things.

The inflation is speeding up. It shouldn't speed up, it should only slow down due to a loss of momentum.

That makes me wonder about currently unseen forces like dark matter. Is it possible that the universe is surrounded by an ever expanding cocoon of dark matter that has a pulling force on all matter making it accelerate? And once the "membrain" (for a lack of a better word) gets too thin, the force is too weak to keep pulling and causes the contraction?

I never favored the finite inflation hypothesis.

I support any challenges to it. The fact that so many "scientists" are willing to vehemently defend an untestable hypothesis shows me they have way too much time on their hands, aren't doing anything productive, and have poor priorities.

a reply to: TerryDon79

If all of the matter in the Universe were compacted into a singularity than wouldn't it collapse inwards upon itself infinitely?

What magical force caused it to suddenly explode outwards against gravity?

I'd prefer a gray hole concept where everything crunches into a microcosm to the infinite extent in such a fasion that it created a Universe where everything only appeared to expand but was actually just crushing inwards with an inverse effect.

This would explain the the ether concept and also quantum entanglement, among other anomalous phenomena.

So in that view distance is an illusion and everything is in reality is located in one infinitely decreasing singularity, and distance rapidly decreases eternally. It may even be at an exponental rate.

Or Alternatively the Universe is infinite in size and materials are distributed throughout endlessly.

Either or.

To me this holds up pretty well.

a reply to: muzzleflash

Not necessarily.

If the singularity has way of releasing the energy (the Big Bang/Great Expansion Theory) then it can expand and collapse.
Or, another explanation is, I don't know

Sure, we don't know everything, but that's why there's so many theories and hypotheses.

O.K.
According to the Doppler effect - seen, tested, proven, demonstrated - the Universe is expanding in all directions.
And scientists believe that some kind of "dark energy" and some form of "dark matter" are responsible for this general "runaway", by exerting a force which overbalances the gravitation.
What if the elusiveness of those "dark forces" is due to the fact that they don't exist at all, and the Universe is actually pulled outwards by an external zone of lower pressure, and the force expanding it is beyond our perceptibility, therefore undetectable ?
This implies of course that the Universe is finite and balloon shaped, more or less...
Don't kill me, if scientists can speculate, why can't I ?

Wonderful!

One of my favorite thought exercises; I have often wondered if the universe is neither expanding nor contracting to any great degree - rather it is our miniscule perspective which is skewed.
Imagine for a moment that you are seated in the back of a truck, facing opposite the direction of travel. Everything appears to be flying away from you! However should you face toward the direction of travel, the opposite is true.

Spin. Rotation is the order of the day - from the smallest molecule up to the largest heavenly bodies we can see this.
It would stand to reason then, that much as planets rotate on their axis AND around their star, that not only do solar systems and galaxies rotate on their axis, but also around some as yet unknown center; perhaps?
Is it possible, that the universe (as we know it) is also rotating?

Now imagine you are back in the back of the truck; and the truck becomes Earth, and everything is moving away from us...

Maybe the universe isn't expanding but all the galaxies are sinking into their own gravitational wells? Would everything would appear to expand outwards towards the galaxy and the rest of the universe would appear to contract away from our galaxy?

Or maybe starlight causes the expansion of the universe? Photons as they travel across the universe gain a red shift and lose energy due to expansion. So where's that energy going? Is it being converted into space-time? Gravity would keep regular matter closely bound in galaxies, clusters, filaments and cosmic sheets, so expansion would occur in those places at equilibrium points betwen two gravitational fields, like the edges of those galactic sheets and filaments.

originally posted by: Astyanax
I have sometimes defended the theory of cosmic inflation in these forums — it explains things like the...

"...scientists are condemned by their unexamined assumptions to study the nature of mirrors only by cataloging and investigating everything that mirrors can reflect. It is an endless process that never makes progress, that never reaches closure, that generates endless debate between those who have seen different reflected images, and whose enduring product is voluminous descriptions of particular phenomena." - The Adapted Mind

The unexamined assumptions are the assumed Universal Reality of 'motion' and 'time' (the in-arguability of our 'perceptions'; 'motion' is obvious...).
That is why 'expansion', as it is conceived, is not possible, and why no 'explanation/theory' can possibly be... 'Universal'!
'Motion' (as first shown by Zeno) and 'time' are not possible, physically or philosophically, thus the inevitable failure of the 'big bang' (as commonly understood) theory, as well as the 'expansion theory', and it doesn't look too good for 'evolution', either! *__-

Perhaps a few words about the scientific background to this are in order. What little we know about the history of the very early universe is derived from studies of ancient light — most of which is redshifted down to infrared or microwave frequencies. The European Space Agency’s Plank space telescope studied the universe in these frequencies until 2013. Scientists have been processing the information obtained, and recently presented the latest results, together with their views about what they meant, to an international conference.

The authors of the inflation critique were at that conference. Their take-out from it was that the new Planck data suggested a very messy and complex early universe in which the chances that inflation occurred the way the most favoured models say it does are very close to zero. They say the new data makes inflation all but impossible.

The establishment, as represented by the 33 senior scientists who wrote a letter of demurral to Scientific American, disagrees.

The main article linked in the OP explains the data and what, in the view of the authors, it shows, in pretty simple terms. I encourage you to read it, and comment on the contents. Then we can have an informed discussion.

a reply to: Astyanax
I've always considered inflation somewhat speculative rather than something that's proven. I got a little more excited about it when there was a "false alarm" about more evidence for inflation as cited in the "...Faces Challenges" link in the OP:

On March 17, 2014, scientists at the BICEP2 experiment at the South Pole announced the detection of cosmic gravitational waves but later retracted their claim when they realized they had actually observed a polarization effect caused by dust grains within the Milky Way.

So while I can't agree with all the claims in the article criticizing inflation, I think even the supporters of inflation would have to agree that more evidence would be nice, something like that which didn't turn out to be unrelated to inflation.

Also the criticism raises the question of why does it have to be a big bang instead of a big bounce?

Although most cosmologists assume a bang, there is currently no evidence—zero—to say whether the event that occurred 13.7 billion years ago was a bang or a bounce. Yet a bounce, as opposed to a bang, does not require a subsequent period of inflation to create a universe like the one we find, so bounce theories represent a dramatic shift away from the inflation paradigm.

The problem I have with the bounce idea isn't mentioned in any of the sources. With current observations showing accelerating expansion of the universe it appears there won't be any collapse or future bounce, so the obvious problem to me is how could a prior bounce have occurred in the same universe? It seems like one would almost have to presume the universe prior to the bounce had different properties to allow it to collapse which our universe doesn't seem inclined to do.

While it doesn't hurt to challenge the status quo, what it will take to replace the current models is a replacement that's better and I don't think a better replacement is being offered at this time. Maybe someday it will be, since inflation is still somewhat speculative, or maybe inflation will be confirmed by detection of cosmic gravitational waves that ends up being verified. Let's go where the evidence leads us.

originally posted by: trisvonbis
O.K.
According to the Doppler effect - seen, tested, proven, demonstrated - the Universe is expanding in all directions.
...
Don't kill me, if scientists can speculate, why can't I ?

Because you don't have your facts straight and facts are the starting point for speculation.

The Doppler effect has been excluded as the cause of cosmic redshift which has been attributed to the metric expansion of space.

Expanding Confusion: common misconceptions of cosmological horizons and the superluminal expansion of the Universe

We analyze apparent magnitudes of supernovae and observationally rule out the special relativistic Doppler interpretation of cosmological redshifts at a confidence level of 23 sigma.

a reply to: Arbitrageur

With current observations showing accelerating expansion of the universe it appears there won't be any collapse or future bounce, so the obvious problem to me is how could a prior bounce have occurred in the same universe?

A well-considered response. But as long as inflation is on the table, the accelerating expansion currently affecting the universe cannot be taken as an indication of future events or trends. The universe could cease expanding and start contracting tomorrow; nothing we know precludes that.

Suppose the universe does expand and contract cyclically. When it contacts in size and bounces, it apparently retains the same laws of nature and physical constants as those we currently experience.

A problem arises-- How is it that all these many factors happened to assume values which are required to produce intelligent life? The odds of this occurring by chance seem prohibitively long.

This problem is recognized, and answered in conventional big bang/inflationary cosmology by supposing that we live in a multiverse.
In this scenario, there are a great many separate universes, each with its own laws and constants. It's not too unreasonable, then, that at least one of these universes (ours) has the necessary combination of conditions to permit our existence.

When I get an explanation for blue outliers, then I'll consider inflation a little more seriously.

a reply to: TarzanBeta

I had to look up blue outliers. They turn out to be radiation sources whose spectra are blue-shifted, implying that they are speeding towards us at relativistic velocities, while neighbouring sources are seen to be red-shifted, ie moving away.

How does their existence impact on the inflation hypothesis? I'm curious.

originally posted by: Astyanax
a reply to: TarzanBeta

I had to look up blue outliers. They turn out to be radiation sources whose spectra are blue-shifted, implying that they are speeding towards us at relativistic velocities, while neighbouring sources are seen to be red-shifted, ie moving away.

How does their existence impact on the inflation hypothesis? I'm curious.

Red-shift is oddly distributed evenly around the Earth, for the most part. That implies inflation, but only as if we're actually the center of the universe... Which would seem ridiculous. The fact that there are blue outliers makes this problem even more preposterous with our current understanding of expansion.

I've considered myself that redshift could have something to do with a change in velocity and not necessarily a change in only direction. If that turns out to be a possibility, then it would explain blue outliers. But then we would have to consider the universe a cyclical machine instead of a bubble expanding into limbo... And of course, there is no way to check for that, as far as I know.