Talk:Cosmic inflation

Relative or absolute expansion?

I second the criticism that a relative inflation of 10^78 doesn't mean anything if an initial dimension isn't given.

The Planck length might be implied here, but this is not universally agreed upon as the starting point of the Big Bang theory of cosmology.

If the initial dimensions of the universe was determined to be 10^-78 of a Planck length to begin with, then an inflation of 10^78 would mean that after that tremendous expansion, the size of universe would be just a single Planck length. Relative vs absolute is what exponents are all about. Any mathematician worth his pencil box knows this property of exponentiation better than his own name.

Asserting that spacetime expanded by 10^78 relative to where inflation began is a throwback to Maxwell's aether theory, absolute space, and time. Given rash assumptions such as these, it is small wonder that the conclusion is that the universe expansion was superluminal. This variety of cosmology is about as convincing as the 10^116 discrepancy in the vacuum expectation value. Concepts like these ceased to be viable shortly after 1905. Danshawen (talk) 03:22, 14 March 2014 (UTC)danshawen

Please cite the text that you are referring to; I don't see the assertion in the article or talk page. I agree that the the article should refer to relative inflation in a specified time interval, but don't understand what you mean by the initial dimensions of the universe. Shmuel (Seymour J.) Metz Username:Chatul (talk) 14:41, 14 March 2014 (UTC)

First direct evidence for the theory of cosmic inflation

Headine-1: BICEP2 finds first direct evidence of cosmic inflation

• http://physicsworld.com/cws/article/news/2014/mar/17/bicep2-finds-first-direct-evidence-of-cosmic-inflation

QUOTE: “Cosmic evolution from the Big Bang to today” [Very popular news coverage, everywhere!] — Charles Edwin Shipp (talk) 00:12, 18 March 2014 (UTC) PS: one reference is in the Article here, but this will explode to more in popular media.

Headine-2: Evidence of young universe's growth spurt is discovered

• http://www.latimes.com/science/la-sci-cosmic-inflation-20140318,0,766934.story#axzz2wKJLhbq0

QUOTE: “Researchers focusing on gravitational waves find the first direct evidence for the theory of cosmic inflation, a faster-than-light expansion just after the big bang.” [One person says the work is worthy of the Nobel Prize.] — Charles Edwin Shipp (talk) 15:39, 18 March 2014 (UTC)

BICEP2 measurement supports inflation, not BBM

I've seen people on the web confused about the meaning of the news about the BICEP2 measurement. I believe a lot of it stems from confusion about the difference between the standard Big Bang model and the theory of inflation. The former is a model of an expansionary universe that goes back to recombination, nucleosynthesis, and baryogenesis, back to 10^-3 seconds or so, while it had a decelerating expansion rate. The latter is a theory during an earlier epoch, at somewhere like 10^-33 seconds, so well before the known parts of the standard Big Bang model, during which the expansion rate was growing exponentially.

I am not a physicist, but as I understand the news, it was an observation supporting inflation. It doesn't seem right to me to say this result supports the big bang theory. If they had not measured any B-Modes, the BBM would not be any less well satisfied today. The results are interpreted in terms of the BBM: they had to subtract off the E-modes and B-modes predicted by big bang, in order to isolate the gravitational wave signal. If the big bang model were wrong, they entire computation would be meaningless, so in no sense can the measurement be said to "support big bang".

Finally, I will note that the NYTimes changed the title of their article from "Detection of Waves in Space Buttresses Landmark Theory of Big Bang" to "Space Ripples Reveal Big Bang’s Smoking Gun" . Perhaps someone made the same complaint to the NYTimes that I am making here: this measurement is not about big bang, and conflating them is at best misleading, but more likely just wrong.

So I have removed the phrase "and for the Big Bang." from the sentence which read "BICEP2 collaboration announced the detection of inflationary gravitational waves in the B-mode power spectrum, apparently providing strong evidence for Guth's theory of inflation, and for the Big Bang". I have also updated the title of the NYTimes article. -lethe ^{talk +} 03:45, 23 March 2014 (UTC)

Reverts

Hello IP editor. Science20.com is not a reliable source. Next time you try to add that back, I will report you for edit warring and your account could get blocked. If the fact is notable you should be able to find evidence of it in a reliable source. Jehochman ^Talk 12:46, 27 March 2014 (UTC)

Edit warring continues under various IP addresses. Maybe this page should be semi-protected ? Gandalf61 (talk) 10:58, 28 March 2014 (UTC)

Submitted request for protection. Aldebaran66 (talk) 16:00, 28 March 2014 (UTC)

Who needs "protection" ? Objective information needs protection, instead of suppressing any "disturbing" contribution. Of course, one can understand that nowadays universities and institutions need money and make a lot of propaganda. But Wikipedia should not follow any scientific "party line".

I semiprotected the article in response to the request. Please check the article and see if the current version is OK. --Orlady (talk) 04:34, 29 March 2014 (UTC)

timeline of the discovery

I just looked at Alan Guth's original PRD paper and found that it was published on January 198*1*, though it was received on Aug 1980. Both the published/received dates of all the early contributions should be checked. — Preceding unsigned comment added by 60.43.120.31 (talk) 22:56, 29 March 2014 (UTC)

Lede - needs edit

The following appears in the lede: "As a direct consequence of inflation, the Universe appears to be the same in all directions (isotropic) and the cosmic microwave background radiation is distributed evenly." This is exactly wrong. (The Theory of ) Inflation is a consequence of our observations, NOT the other way around. It is NEVER correct to claim a theory results in observations.173.189.77.96 (talk) 20:43, 13 April 2014 (UTC)

The problem results only from your insertion of the words "theory of". The physical phenomenon "inflation" certainly can lede to observations. "The theory of" inflation as you would put it, simply is the hypothesis that inflation happend in the early universe. And you are correct that one of the reasons to posit this hypothesis is that it explains why we observe the universe to be isotropic at large scales.

Your last assertion is manifestly wrong. E.g. It is quite correct to assert that: "the theory of spontaneous symmetry breaking has led to observation of the Higgs boson." (i.e. theoretical predictions are often a reason to look for certain things).TR 08:43, 14 April 2014 (UTC)

I disagree with your claim that inflation is a physical phenomenon. Inflation is, by your claim, real and hence irrefutable, correct? Please cite a single peer reviewed source that has made this amazing (theological) claim.

The article should state that IF inflation happened then it would result (as we now understand it) in a Universe with an appearance similar to ours. As far as your assertion that theory leads to observation, you're just logic-chopping; but you may be right that for the average reader such a narrative device is useful. Were both WWII and Yang-Mills "significant" in "leading" to the LHC? What historical fact did not "lead" to it? I also note that inflation is not well constrained enough to qualify as Theory of Physics (in the formal sense, and as (well) described in the lede). I maintain my STRONG objection to any statement that ANY facts are consequences of ANY theory.216.96.79.20 (talk) 16:05, 21 April 2014 (UTC)

lol.TR 21:36, 21 April 2014 (UTC)

How can inflation smooth out initial inhomogeneities?

Can someone explain why an exponential expansion shouldn’t just enlarge the scale of initial inhomogeneities –instead of smoothing them out as the inflation is designed to do?Antonquery (talk) 03:28, 28 April 2014 (UTC)

Don't understand the question. Unless it's a fractal (which some critics like Penrose say it could be), enlarging a scale generally smooths it out. Rolf H Nelson (talk) 03:51, 29 April 2014 (UTC)

Would you please explain why enlarging a scale smooths out inhomogeneities? Antonquery (talk) 07:41, 9 May 2014 (UTC)

Simply put, unless its fractal, inhomogeneities have a minimum length scale. Given enough e-foldings of inflation this length scale becomes larger than the observable universe. The result an observable universe that has no inhomogeneities. tadaTR 11:55, 9 May 2014 (UTC)

I still don’t get it and the e-folding page also isn't much help. If and when e-folding actually does smooth out inhomogeneities, then does this mean that the reverse process creates inhomogeneities? Antonquery (talk) 01:24, 10 May 2014 (UTC)

Unless the universe is fractal, There are a finite number of inhomogeneities in a given unit volume. Therefore the universe post-inflation has fewer inhomogeneities per unit volume than before inflation, and is therefore smoother. The reverse process doesn't create inhomogeneities, but rather clusters them together. Rolf H Nelson (talk) 23:49, 24 May 2014 (UTC)

Inflation theory was devised by Alan Guth AND Andrei Linde.

The ingredients for inflation theory were laid by Andrei Linde, afterwards Alan Guth proposed his theory (which was wrong in a way) and months later Andrei Linde developed THE Inflation Theory as we know it today.

So I think the second paragraph of the article should be modified. — Preceding unsigned comment added by 189.128.157.149 (talk) 08:41, 11 May 2014 (UTC)

FTL expansion?

The first sentence of the introduction describes inflation as a period of faster-than-light expansion. I find this at best misleading. Metric expansion does not involve the FTL movement of objects in the sense of propagation (e.g. of waves) in the space. If we mean the increase in distance between hypothetical far-apart objects over time, then any metric expansion could be dubbed superluminal if we pick two objects which are far enough apart, since apparent relative velocity is basically

velocity = Hubble * distance

Did the original author want to allude to the fact that for this kind of exponential expansion, the comoving horizon becomes smaller? But that's not the same thing as FTL movement.

My main worry is that due to the choice of words "faster than light" in such a prominent location, it lets inflation appear to be in conflict with relativity to the casual reader, while it really isn't. Aknochel (talk) 09:59, 13 May 2014 (UTC)

Ok, since noone had any comments, I've deleted the statement about faster than light and put a more general "rapid" Aknochel (talk) 22:02, 30 May 2014 (UTC)