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I asked in this question if type Ia supernovae could be different in the past. According to me, this would imply that the existence of dark energy would not be so certain.

After reading the answer to it I read this article (2011), in which it is claimed that measurements on the CMBR provide more in favor of dark energy.

One can read in this article:

Dark energy acts to counter the emergence of structures within the universe. A universe with no dark energy would have a lot of structure. As a result, the CMB photons would undergo greater lensing and the fluctuations would deviate more from the original Gaussian distribution.

And:

However, the opposite was found to be true. “We see too little lensing to account for a universe with no dark energy,” Sherwin told physicsworld.com. “In fact, the amount of lensing we see is consistent with the amount of dark energy we would expect to see from other measurements.”

On Wikipedia one can read:

Confirmatory evidence has been found in baryon acoustic oscillations, and in analyses of the clustering of galaxies. The accelerated expansion of the universe is thought to have begun since the universe entered its dark-energy-dominated era roughly 4 billion years ago.

So, obviously, if dark energy exists this accelerates the expansion and has an effect on the structure of matter (including CMBR?) in the universe, which leads to the observed structure today. In the past (before 4 billion years ago) the universe was expanding "normally". Wasn't most structure already formed then? Without dark energy (it's not that I don't believe it exists but I'm just wondering)?

So my question:
Could it be (by still unknown causes) that the structure(s) of matter in the universe (galaxies, clusters, superclusters) is how it is but without the alleged accelerated expansion (and thus dark energy)? Of course, the answer is yes, but does such a mechanism is indeed proposed? All research is devoted to dark energy (in this context). Could it be that we are fooled by the observations? Or even maybe prejudice? After all, the wish can be the mother of observations.

Deschele Schilder
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    It seems like the article you cited already answers the question very clearly. I am not sure what you are looking for here. – Dale Feb 03 '20 at 12:37
  • @Dale Read my last two lines. What's unclear about it? – Deschele Schilder Feb 03 '20 at 14:51
  • obviously, if dark energy exists this counteracts the expansion No, it doesn’t. It accelerates the expansion. You have gotten it backwards. – G. Smith Feb 03 '20 at 17:04
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    Your question is clear, but it is also clearly answered. “We see too little lensing to account for a universe with no dark energy,” So you cannot be looking simply for the answer to your stated question since you already have that answer. So what else are you looking for? – Dale Feb 03 '20 at 17:50
  • I try to find out if all these observations can be explained without dark energy. Is it possible that another mechanism than accelerated expansion is responsible for the observations? – Deschele Schilder Feb 03 '20 at 22:19
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    Thank you for the clarification. This makes more sense now. – Dale Feb 03 '20 at 22:25
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    Are you perhaps asking, "What could produce the observational evidence for accelerating expansion if there isn't such an acceleration?"

    As phrased, the question title seems to be asking something which is more epistemology than physics. "Could it be (despite all data pointing to the contrary) that the Sun revolves around the Earth?"

     – xzackli Feb 03 '20 at 22:50
  • @G.Smith You're right. I'll edit. – Deschele Schilder Feb 04 '20 at 00:46
  • @xzackli No, I'm questioning the accelerated expansion (despite the alleged evidence) and hence dark energy. That the Earth revolves around the sun seems pretty clear to me. – Deschele Schilder Feb 04 '20 at 00:53
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    https://physicsworld.com/a/the-dark-energy-deniers/ – alanf Feb 04 '20 at 13:33

2 Answers2

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Could it be (by still unknown causes) that the matter distribution in the universe (galaxies clusters, superclusters) is how it is but without the alleged accelerated expansion (and thus dark energy)?

There is an infinite number of possible models and a finite set of observed data. Therefore it is reasonable to assume that there is always an infinite number of models that can explain any given set of data. So the answer to questions like this is always “yes”, and therefore the question itself is not very informative.

It takes no effort whatsoever to postulate that a different unknown cause produces a given effect. The hard part is actually proposing a specific mechanism. Although there is an infinite number of possible models, the fraction of possible models that are also consistent with the data is very small.

So proposing a model that explains the existing data is a large accomplishment in itself. When that model then also explains future data and data collected by many different techniques and mechanisms the model gains substantial credibility. Hoping for an unknown mechanism to avoid part of the model is merely wishful thinking. Yes, it is likely that such models exist, but we may never find them and there is no guarantee that they will perform better than the current model in other situations.

Deschele Schilder
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Dale
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Sure it's possible, and many people have thought about it. See the sources cited in this section in the Wikipedia article on Dark Energy.

Caveat: the odds are these papers are wrong, e.g. here's a rebuttal to one of the papers. If the arguments are too technical to follow, here's a writeup of another observational skepticism paper at a more accessible level.

Allure
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