Talk:Metric expansion of space

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Former good article Metric expansion of space was one of the Natural sciences good articles, but it has been removed from the list. There are suggestions below for improving the article to meet the good article criteria. Once these issues have been addressed, the article can be renominated. Editors may also seek a reassessment of the decision if they believe there was a mistake.
Article milestones
Date Process Result
August 30, 2006 Good article nominee Listed
February 15, 2008 Good article reassessment Delisted
Current status: Delisted good article

"Metric for Earth's surface" virtually incoherent[edit]

The introductory material -- particularly "Metric for Earth's surface" -- is meaningless for laypeople like myself. The section points out that we may specify points on the surface of the Earth using either X-Y-Z cartesian coordinates or latitude and longitude, and then states wholly without justification "Once we have chosen a specific coordinate system, [...] the appropriate metric is mathematically established too" at which point the idea of a metric, its relevance to spherical geometry, or why this entire section is included in the article at all is never again discussed despite the fact that section goes on for a number of sentences about geodesics and airplanes. It's possible that whomever wrote this was attempting to convey to me and to other readers who are not intimately familiar with the idea of a metric something about the distance between local points being the same irrespective of the choice of coordinate system (cartesian or latitude-longitude) but I can't be sure. — Preceding unsigned comment added by (talk) 08:14, 20 December 2016 (UTC)

Contention That Evidence of Expanding Universe has been Misinterpreted[edit]

Following some edits to make this a bit more concise and to overall improve the writing, I would add the below as a section to the main article:

Expanding universe, smechspanding schmuniverse. I'm sorry but I believe that the astrophysicists are wrong. They've concluded that the universe is expanding based on one observation, an observation that I would say they may have misinterpreted. And they've gone down the path of inventing a bizarre hypothesis to try explain the contradictions between their conclusion and accepted and proven physics - rather than going back and correcting their error.

Let me explain. A while back some scientists happened to notice that light from distant objects (stars and galaxies) in space was red-shifted. Upon closer observation they learned that the more distant the object the bigger the red shift. And this was the case no matter which direction you looked. Interesting...

Redshift of light is nothing new. Einstein developed theories that said redshift occurs in the light sourced from an object when that object is moving away from you. Information on redshift: . Other people have gone on to measure light from objects that are moving away from us at known speeds and have proven Einstein correct in this - light sourced from objects moving away is indeed red shifted, and redshift increases as the departing velocity increases.

But there is nothing that says that there could not be other phenomena that might cause redshift.

When the scientists found redshift assiociated with distant space objects they jumped to the conclusion that they were moving away from us - and from only this one piece of evidence they went on to conclude the universe is expanding. But then, there was an issue with this idea. In a uniformly expanding universe the relative velocity between two objects grows in proportion to the distance between the objects. Based on the observed "expansion rate" of our universe if two objects are > 4.5 gigaparsecs apart then the relative velocity between the objects will exceed the speed of light. Since it is well established that the speed of light cannot be exceeded, you either have to question the expanding universe hypothesis, or you have to invent some new concept that says you're really not exceeding the speed of light, something else is going on.

The concept invented was that the objects are not really moving apart from each other, rather the space between them is just expanding. Whaaaat?!! And then, on top of this, the theorists added the qualifier that the expansion of space is happening only on cosmic scales - this would explain why we don't see any "expansion of space" when we do precise measurements on things like the distance between the moon and the earth. Other theories have been formulated, and more are being formulated as we speak, to explain more of this picture of an expanding universe and to try to reconcile it with known and proven physics.

In my opinion the astrophysics community is long overdue take a big step back and re-consider the original, and in my belief mistaken, notion that the redshift of light from distant objects is proof that the universe is expanding.

So what alternative interpretation of the observed redshift could there be? Consider this: maybe light ages as it propagates across the universe. And as it ages, it loses energy - hence the red shift. Because of the fixed speed of light, light that we observe originating from more distant objects is of course older. So this ageing hypothesis explains the observed increased red shift with distance - without having to conclude that the universe is expanding, and without contradicting known and proven physics.

How would a person go about proving that light becomes red shifted as it ages? Well, how about shining some light at the moon and then precisely measuring the wavelength of the reflected light that comes back? — Preceding unsigned comment added by Keithsinterweb (talkcontribs) 18:20, 8 December 2012 (UTC)

That idea is called Tired Light, and it has already been considered, and rejected for lack of any supporting evidence, by the scientific community. Perhaps you should read about the observational evidence for the concordance cosmology, which is much more than just the observation that redshift and distance are correlated. Contrary to your assertion, the observed expansion of space does not contradict "known and proven physics", whereas any viable tired light hypothesis most certainly would. - Parejkoj (talk) 15:30, 9 December 2012 (UTC)
Just like Earth is not flat, maybe the Universe is neither. A negatively curved static Universe would also provide this redshift. The Euklidian expanding Universe is a good linear approximation of negatively curved space Hilmer B (talk) 15:01, 23 June 2015 (UTC)

Red shift[edit]

All units in space times are imperfect. This means that they change, ether continuously or quantitatively, depending on the unit of measurement ‘now’ of the observer. The change is the difference in the unit observed in two ‘now’ of the observer. The units of change are additive and the sum manifests itself as an interval of time but also as the big difference between the beginning ‘0’ and the end ‘1’ in the transformation, or an evolution, contained within the space (0<1). Motivation for change originates in the immaterial space time. It causes, for example, quantitative change (explosion) of the neutron after 15 minutes. Applied to a photon the change is the ‘red shift’ in the units of electromagnetism. KK ( (talk) 13:03, 14 January 2013 (UTC))

lol, WP:NOR.1812ahill (talk) 17:14, 28 October 2013 (UTC)

I have a problem with "gravitationally bound/unbound"[edit]

I suppose that basically Newton is still applicable here. Gravitation is inversely proportional to distance squared, a decent continuous function - no bumps. Thus, between two masses, depending on their distance yes but nevertheless, there is always gravitational attraction, near and far, all the way towards infinity. So in my opinion, two bodies are always gravitationally bound, regardless of distance. The link to explain "gravitationally unbound" points to an article on archery (?), it does in no way explain the difference between "bound" and "unbound". Yet I get the impression that in case of "bound" there are no traces of any Hubble expansion (the distance between Earth and Moon is indeed increasing, but only due to tide) and in case of "unbound" it is 100% Hubble. There seems to be no 50% in between. I think that this discontinuity should be explained. Especially if it disqualifies Newton's equation (Wouldn't that be a sensation!  ;-) So what I'm asking for is a decent explanation of "gravitationally bound/unbound". The current one is not. / Ola — Preceding unsigned comment added by (talk) 15:50, 20 June 2013 (UTC)

virial theorem would be a more natural redirect. Thanks. jps (talk) 03:11, 20 January 2014 (UTC)
Not quite... Slightly better, but it still doesn't provide the criteria that helps you decide whether a pair of arbitrarily chosen objects in the universe are "gravitationally bound" or "gravitatiionally unbound". I'll just remove the link. Hilmer B (talk) 16:19, 27 June 2015 (UTC)

How the current explanation for the Cosmological Red-Shift, based on ‘metric-expansion-of-space’, can not be correct[edit]

In a paper recently published in Adv. Studies Theor. Phys., Vol. 7, 2013, no. 20, 971 - 976; titled: "Wave-Theoretical Insight into the Relativistic Length-Contraction and Time-Dilation of Super-Nova Light-Curves" by Hasmukh K. Tank, a sub-section reads as follows: "2. How the current explanation for the Cosmological Red-Shift, based on ‘metric-expansion-of-space’, can not be correct: Currently, the cosmological red-shift is understood in terms of ‘metric-expansion-of-space’. It is believed that after the big-bang the space-time started expanding; so the distances between galaxies are increasing, even at the rates faster than the speed of light, near the edge of the universe. So, the wavelengths of extra-galactic-photons get stretched with the expansion-of-space, resulting in the observed ‘cosmological-redshift’. Now, I present here an argument that this explanation can not be correct, as follows. Accepting that the space between the galaxies is expanding; but the space within the galaxies is not expanding, because galaxies are gravitationally bound structures. So, there has to be a smooth transition, from the expanding-space out-side the galaxies, to the non-expanding-space within the galaxy. Now, when the extra-galactic-photons, after their long-long extra-galactic-journey, with their wavelength stretched due to ‘expansion-of-space’, enters the ‘transition-region’ from expanded-space to ‘non-expanded-space’, then their wavelength should start shrinking-back, like it shrinks while entering stronger and stronger gravitational-field; and when they enter the non-expanded-space of our milky-way-galaxy, their wavelength should shrink-back to original wavelength! Isn’t it? Therefore, the current explanation for the ‘cosmological-red shift’, which is based on ‘metric-expansion-of-space’, can not be correct. Every scientist has accepted my argument, that: “there has to be a smooth transition, from the expanding-space out-side the galaxies, to the non-expanding-space within the galaxy” when I attempted to explain galaxies’ rotation-curves based on this smooth-transition of expansion-of-space. This has encouraged me to think of ‘shrinking-back’ of stretched-wavelength of extra-galactic-photons while entering the non-expanding-space of our milky-way-galaxy." (talk) 16:39, 22 October 2013 (UTC) (talk) 16:43, 22 October 2013 (UTC) Regarding The Accelerated-Expansion of Space, this paper has this to say " This author has recently proposed four alternative-interpretations for the ‘cosmological-red-shift’ [3-5]. According to these new interpretations the red-shift depends only on distance traveled by the extra-galactic-photons, not on the relative-velocity of the source-of-light and observer. Therefore, as the photons travel a unit-distance, say one light-year, then there is certain amount of red-shift; say the frequency of photon which was f0, reduces to f = f0 / 1.1. Then for the next unit-distance f becomes the new input frequency which gets red-shifted to f / 1.1 = f0 / ( 1.1)^2. Then for the third unit-distance, new value of f = f0 / (1.1)^3. Thus the red-shift-distance-curve becomes automatically non-linear, as observed, without invoking any ‘dark-energy’. Perlmutter and Riess based their interpretation of non-linearity of red-shift-distance-curve, on the current, ‘metric-expansion- of-space-based-explanation' for the cosmological-red-shift, so they needed invocation of ‘dark-energy’[6,7], whereas here in section-2, we found that ‘metricexpansion-of-space’ can not explain the observation of the ‘cosmological-red-shift’. Thus there has been a need for considering alternative ways to understand ‘relativistic-length-contraction’, ‘time-dilation’ and the observations of ‘cosmological-red-shift’. (talk) 08:11, 23 October 2013 (UTC)

Time-dilation of super-nova light curves can also be alternatively-explained

In a paper recently published in Adv. Studies Theor. Phys., Vol. 7, 2013, no. 20, 971 - 976; titled: "Wave-Theoretical Insight into the Relativistic Length-Contraction and Time-Dilation of Super-Nova Light-Curves" by Hasmukh K. Tank, time-dilation of super-nova light-curves is alternatively-explained as follows: 3.2 Explanation for the Time-dilation of Super-Nova Light-Curves: Super-nova-light-curves, described by Giacobbe, [2], can be viewed as a ‘gate-function’ in the ‘time-domain’; and it can be Fourier-transformed into frequency-domain; and it is this wide band of waves which travels in space and reaches us after millions of years. During its travel, when this wide-band of waves, being electromagnetic waves, gets red-shifted due to any mechanism then its band-width shrinks in the frequency-domain; so when it is transformed back into time-domain we find that the duration of the curve has got increased. Thus, time-dilation of supernova-light-curves is not an independent observation from the observations of the‘cosmological-red-shift’ due to any mechanism. Thus this paper reaches two interesting conclusions regarding the two predictions of General Relativity: 1. Metric-expansion-of-space can not explain the observation of the 'cosmological-red-shift' because if the wavelength can streatch due to expansion-of-space, then it should have got shrunk while entering the 'transition-region' from 'expanding-space-between-the- galaxies' to 'non-expanding-space-within-our-milky-way-galaxy'; and 2. 'Time-dilation-of-super-nova-light-curves' can be explained by any alternative-explanation for the 'cosmological-red-shift', i.e. observations of time-dilation-of-super-nova-light-cureve are not the exclusive tests of General Theory of Relativity. (talk) 16:31, 25 October 2013 (UTC)

I may be wrong, but I'm surprised that a journal as prestigious as "Advanced Studies in Theoretical Physics" doesn't have an entry in that font of all knowledge, namely Wikipedia, particularly as it has now reached the grand old age of 7. I'm also surprised that its publisher (Hikari Ltd.) is also not worthy enough to have found its way into Wikipedia, unless of course it is this Hikari company (ROFL).1812ahill (talk) 17:54, 28 October 2013 (UTC)

Hikari company mentioned in the above post is different from the publishers of the journal Advanced Studies in Theoretical Physics. Company mentioned in the above post is Japan-based food company; whreas Hikari Ltd. is based in Bulgaria, publishing various scientific journals, and books, like Springer publishers. Their web-site-address is (talk) 15:08, 30 October 2013 (UTC)

Independent sources will be required before such "alternatives" can be addressed at this article. jps (talk) 03:16, 20 January 2014 (UTC)

Restored some text, moved some other text into a new section, tried to fix some of the heaviest non-sense[edit]

This article is complete chaos. The "sources" given are in most cases not real "sources" of research, but links to some sort of apparent authority upon some part of research somehow related to a subject related to the title of this article.

The article is heavily biased and does NOT express various views upon the exact nature of this expansion, even if we would accept without question that the universe is indeed expanding. Even those who believe so are in great disagreement about how to incorporate such a fact into a general theory, of which there are as many different versions as may be expected in a subject of this scale and complexity.

Large parts of the article is written in vernacular, "popular" or "American" English. This renders the article severely imprecise.

The question remains whether wikipedia should unanimously proclaim something absolute "truth" or not! If not, it should be clear that we are dealing with theories, and that several conflicting theories exist. Most important of all, it should be clear to all readers that the man after whom the "Hubble constant" and "Hubble's law" were named, did not himself from at least 1936 to his death in 1953 support an expanding universe interpretation. — Preceding unsigned comment added by (talk) 07:51, 3 December 2013 (UTC)

This strange interpretation that Hubble didn't support the expanding universe is making a lot of hay out of two papers on the interpretation of his eponymous law. The quotes are apt and interesting and the full story is told by Norriss Hetherington in his various books, but, suffice to say, Owen Gingerich has the correct answer. Hubble wasn't one to believe or disbelieve. He simply put forward observations and made conclusions as best he could. That he messed up in getting too large a Hubble Constant is an interesting part of the story, but it is by no means the entire story. jps (talk) 03:15, 20 January 2014 (UTC)


Definition of "Stationary" must be provided[edit]

"if it were possible to place a tape measure between even stationary objects, one would observe the scale of the tape measure changing to show more distance between them." -- sorry, then the objects are not stationary. Obviously, an unusual definition of "stationary" is being used, but this has to be defined first. Otherwise I could claim that an airplane flying away at 600km/h is actually stationary relative to me and it's just the space between us two which is expanding. (talk) 20:04, 14 December 2013 (UTC)

False claim: tracking a straight line doesn't measure distance[edit]

"this distance can be measured by tracking a straight line between two points" - that's an obvious nonsense. Try it. Take two nails, hammer them into a board at random location and take a piece of string. Connect the nails with a taught piece of the string. Now "track the straight line" (like with your finger). Do you know the distance now? Of course not! All you know is just the points through which the straight line goes! You need more than just "tracking a straight line between two points" - a kind of tape measure which spits out something like "14.3" or "8.87" and on top of that you even have to know what units these numbers are calibrated in. This sentence needs to be replaced with a different sentence which is not patently false. (talk) 20:12, 14 December 2013 (UTC)

Thanks for the notes[edit]

Thanks for the notes, I have tried to address all of your concerns. jps (talk) 03:15, 20 January 2014 (UTC)

A New Contributor to the Non-Linearity of Red-Shift-Distance-Curve Observed by Perlmutter and Riess: Namely the ‘additional-Red-Shift’ Caused Due to the ‘rate-of-Change-of-Brightness-with-Distance’[edit]

In a pre-print titled: "A New Contributor to the Non-Linearity of Red-Shift-Distance-Curve Observed by Perlmutter and Riess: Namely the ‘additional-Red-Shift’ Caused Due to the ‘rate-of-Change-of-Brightness-with-Distance’" is posted at 'viXra:1402.0058 [pdf] by Hasmukh K. Tank; whose abstract reads as, which may be found interesting: "According to the inverse square law, the brightness of every source-of-light reduces with distance. And the rate of reduction of brightness at various radial distances keeps on reducing with distance. From our experience of ‘amplitude-modulation’, we know that change of amplitude of a stable, single-frequency-source produces a wide spectrum, depending upon the ‘rate-of-change-of-amplitude’; so the varying ‘rate-of-reduction-of-brightness’ with distance of the galaxies and super-novae, must have contributed ‘additional-red-shift’; in addition to the well known Doppler-shift. It is proposed here, that: since this ‘additional-contribution-to-the-red-shift’ is non-linear, the ‘red-shift-distance-curve’ observed by Perlmutter and Riess shows non-linearity; but this ‘additional-contribution-to-the-red-shift’ does not mean ‘additional-recession-of-galaxies’ and ‘accelerated-expansion-of-the-universe’ Bold text" (talk) 10:25, 12 February 2014 (UTC)

About Effects of expansion on small scales

I have read this section while searching for the answer to a question I have, but I was not able to find this answer… because – IMHO – this section fails to make clear the distinction between expansion of space on one hand, and recession of objects on the other.

I know that the neighbor galaxy Andromeda navigates towards our galaxy at about 300 km/s, despite the fact that, according to the Hubble's law, the space should be expanding between both objects at about 50 km/s.

I am not fluent in cosmology, I am just an amateur in astronomy who wants to know:

- if the expansion of space is acting everywhere, at any scale…

- or if the expansion of space is not acting at small scale.

Saying this differently:

- Is the Effects of expansion on small scales just a signal-to-noise issue? Is space always expanding between two objects, whatever be their mutual distance? Is the relative velocity between two objects always the superposition of the objects speeds relative to their local space and the expansion of the space between them, at any scale… making that close objects may show no mutual recession?

- or is there truly no space expansion between close objects?

Sorry if my English seems strange, I usually speak French…

Thanks in advance,

Pehachem (talk) 16:59, 13 June 2014 (UTC)

Video clip showing galaxies moving "apart "[edit]

When observed from this vantage it is indistinguishable whether they are actually moving apart or are shrinking. While their respective centers of gravity remain the same distance apart. This would satisfy both ideas. Their centers of gravity are remain at constant distance while the light does travel longer distance. 2601:C:3600:46B:5D02:835C:3D28:D9CE (talk) 03:30, 13 February 2015 (UTC)

The absolute distances between the centres of galaxies shrink too, but at a lower rate. A cluster of galaxies is less dense than one of the galaxies. In accordance with the inverse-square law, a galaxy shrinks faster than a cluster of galaxies: (talk) 06:55, 16 February 2015 (UTC)

Why a new version of the article is needed[edit]

The current mainstream theories of the metric expansion of space ignore the fact that the proton is a matter wave undergoing an exponentially accelerating self-gravitational blueshift. That is why all current mainstream theories are patent nonsense. — (talk) 09:23, 16 February 2015 (UTC)

This is nonsense, Wikipedia writes what the "mainstream theories" say, per our verifiability policy. Sam Walton (talk) 10:01, 16 February 2015 (UTC)
Wikipedia's verifiability policy of "authoritative" sources is based on a logical fallacy known as argument from authority. Therefore, Wikipedia's verifiability policy is fraudulent. — (talk) 10:16, 16 February 2015 (UTC)
Wikipedia is an encyclopedia, and not a vehicle for original research. We do not aim to be correct, merely verifiable and consistent with the major viewpoints on the topic. It is not our role to try and change the scientific understanding of this topic, but merely for follow the lead of scientific community. There are academic journals and other avenues for shaping scientific opinion and reporting new ideas, but Wikipedia is not one of them. Dragons flight (talk) 10:32, 16 February 2015 (UTC)
"It is not our role to try and change the scientific understanding of this topic, but merely for follow the lead of scientific community."
The current mainstream "understanding" of this topic is patently illogical, and, therefore, unscientific. The so-called "scientific community" is no longer scientific. It is brain-dead. — (talk) 11:17, 16 February 2015 (UTC)
In short, we don't really care what individual editors think about the current understanding of a topic. To enter our own thoughts would be original research and isn't what Wikipedia is for. Sam Walton (talk) 11:36, 16 February 2015 (UTC)
What exactly is original research in the proposed version? Do not say "everything". Quote particular sentences and specify what exactly in those sentences is original research. — (talk) 11:40, 16 February 2015 (UTC)
...Everything. None of it is found in the sources you've cited. Sam Walton (talk) 11:44, 16 February 2015 (UTC)
By saying "everything is original research" or "it does not seem right", people imply that they are totally clueless in the topic. Quote particular sentences and specify what exactly in those sentences is original research. Otherwise, you are a clueless paid troll. — (talk) 11:55, 16 February 2015 (UTC)
Please read the original research page I linked above and come back and explain where in the citations you've provided the information you've written is. Sam Walton (talk) 12:12, 16 February 2015 (UTC)
Now it is confirmed. You are a clueless paid troll. (talk) 12:26, 16 February 2015 (UTC)
Ha, and who exactly is paying me to 'troll' an article on the metric expansion of space? Sam Walton (talk) 12:32, 16 February 2015 (UTC)

All the statements in the proposed version of the article are attributable in accordance with the following policy:

For example: the statement "the capital of France is Paris" needs no source, because no one is likely to object to it and we know that sources exist for it. The statement is attributable, even if not attributed.

Sam Walton's demand to provide sources for "everything" is obstructive trolling in violation of the above policy, which says that an inline citation to a reliable source must be provided only for anything challenged or likely to be challenged. So, which sentence exactly do you challenge in the proposed version? (talk) 13:33, 16 February 2015 (UTC)

Please tone down your personal attacks. The policy you linked above states that "a source must exist even for material that is never challenged." This means that even assuming that what you've written is obvious and not requiring a citation (which I outright disagree with), sources must be able to be shown if the material is challenged, and since I'm challenging you here, the onus is on you to provide citations for your proposed version of this article. Sam Walton (talk) 14:22, 16 February 2015 (UTC)
  1. Being not a person, you cannot be an object of personal attacks.
  2. A challenge must be specific.
  3. Creep off. (talk) 16:13, 16 February 2015 (UTC), can I suggest that if you want to work on a new version of this article that you create an account and use your sandbox rather than writing it here? Sam Walton (talk) 20:06, 16 February 2015 (UTC)
You can't. — (talk) 20:29, 16 February 2015 (UTC)
If you want to completely rewrite this article you need to gain consensus for the change here first, you have been reverted by multiple editors now and all you're going to achieve is the protection of the article. I stand by my above comments that the new article is not suitable. Sam Walton (talk) 10:43, 6 March 2015 (UTC)

Proposed new version of the article[edit]

The metric expansion of space, also known as the cosmological redshift, is an illusion accompanying the hierarchical gravitational collapse (self-gravitational blueshift) of the continuum's matter waves.[1][2] In accordance with the inverse-square law, small objects collapse faster than bigger objects:

The evolution of the cosmic structure is hierarchical: gravitational collapse first builds small objects—galaxies—and then larger structures—clusters of galaxies. Clusters tend to move toward each other and form filamentary structures, flat and elongated.

Thinking Inside the Box The University of Chicago Magazine, 2002

An individual proton is a smaller object than a group of two protons. That is why an individual proton collapses (self-gravitationally blueshifts) faster than a group of two protons, so that the apparent distance between the surfaces of the protons increases, despite the fact that the absolute distance between the centres of the protons decreases.

Expansion of the Universe - distance measures problem.gif

On the above animated sequence, metric squares expand relatively to two constant-size protons, which are chosen as the reference frame.

If we choose the metric squares as the reference frame, then their size will be constant. Initially, the protons will have gigantic sizes (in the beginning of the above animated sequence, each of the protons is as big as a metric square) and will touch each other (in the beginning of the above animated sequence, the two protons touch each other), while the distance between their centres will be maximal. The protons will then begin to shrink, so that a growing gap will appear between their surfaces; simultaneously, the centres of the two protons will begin to move towards each other, but too slowly to offset the "spatially separating" effect of the shrinkage of the individual protons.

In an electromagnetic field, the electric field needs a period to create a magnetic quantum of action called "photon". The metric expansion of space and the concomitant metric redshift of photons exponentially accelerate, so that eventually, the period's metric extension outpaces the period's elapsing, at which point the electromagnetic field loses its actual component (photon). It could be shown on the above animation as an emitted photon that gradually reddens and eventually disappears at a certain distance from its origin. The above animation is incorrect because it does not show the photon's reddening.

  1. ^ Wiltshire, David L. ♦ Gravitational energy as dark energy: cosmic structure and apparent acceleration 10 February 2011, p. 2 ♦ "The basic idea, outlined in a nontechnical manner in ref. [7], is that as inhomogeneities grow one must consider not only their backreaction on average cosmic evolution, but also the variance in the geometry as it affects the calibration of clocks and rulers of ideal observers. Dark energy is then effectively realised as a misidentification of gravitational energy gradients."
  2. ^ Shiga, David ♦ Is dark energy an illusion? New Scientist, 30 March 2007

Semi-protected edit request on 25 February 2015[edit]

Change "is being created" to "fills in" (talk) 19:48, 26 February 2015 (UTC)

Yes check.svg Done As this seems to be a change in regards to perception (and there a edit request backlog) I'll make this change once. Mlpearc (open channel) 22:18, 26 February 2015 (UTC)

Question deleted?[edit]

Why was my question about the animation showing the redshift event deleted?? (talk) 02:28, 8 March 2015 (UTC)

It was initially deleted by an IP because it was asked in two different places [1]. There's no reason to do that. Unfortunately the IP later deleted even the other variant when incorporating their answer in to an earlier comment of theirs [2]. I've readded the second version since amongst other things, their above comments suggest you probably shouldn't trust the IPs answer as their understanding appears to generally be either fringe or pseudoscience. Nil Einne (talk) 07:08, 8 March 2015 (UTC)

Galaxy Animation.[edit]

this animation shows the light eventually reaching the other Galaxy. Shouldn't there also be one showing the event where it never reaches the other? (talk) 02:03, 4 March 2015 (UTC)

Actual real time distance[edit]

When cosmologists are recording distances of certain objects which have been determined are in fact moving away from us due to expansion, can they factor exactly how far the object is at present? If yes, which distance is actually used for the record? Or does it depend on what is being researched? (talk) 02:56, 8 March 2015 (UTC)

As far as I understand the theory, you are asking for the Proper length according to General Relativity. However, there are a lot of assumptions to be made, e.g. that the object has moved following the Hubble flow. We know nothing about what (formerly) distanct object are now, since speed of light is finite. In the meantime, the object might have been exploded, or whatever. (talk) 12:28, 5 August 2015 (UTC)

Exactly! - what is _this_ supposed to mean?:[edit]

Quote from the article: "At the end of the early universe's inflationary period, all the matter and energy in the Universe was set on an inertial trajectory consistent with the equivalence principle and Einstein's general theory of relativity and this is when the precise and regular form of the universe's expansion had its origin (that is, matter in the Universe is separating because it was separating in the past due to the inflaton field)." "INERTIAL TRAJECTORY"!? Is someone here getting cold feet, suggesting that space isn't really expanding, but is rather exploding like a July 4th firecracker? As I have understood expansion, all things are (almost) at rest, it is only empty space between them expanding - as is also clearly stated already in the initial paragraph of the article. Would anyone smash up buttons if I just deleted this paragraph? Hilmer B (talk) 22:38, 28 June 2015 (UTC)

The Hubble flow can be described as entirely inertial consequence of the initial velocity field after the big bang. It can also be described as space expanding. Either description is equally valid. Dragons flight (talk) 08:26, 3 July 2015 (UTC)
Agree. I think that this should be included in the Declaration of Human Rights, section Right of Choice: "Everyone has the right to define his/her own frame(s) of reference". ;-). But my point is that this article flutters between these two different frames - sometimes moving objects and sometimes expanding void. Maybe not to you and me, but to Wikipedia's general target audience, this might be very confusing.Hilmer B (talk) 10:39, 3 July 2015 (UTC)
Firstly, I don't see why the paragraph needs to mention the inflationary period or the inflation field - the matter was separating in the past, or 'after the big bang (link)'. The rest of it loses the basic idea in the complications. But is the paragraph even correct? In the LCDM model the expansion can accelerate in a non-inertial way. There are non-inertial motions going on. If the paragraph isn't even strictly correct, and confusing anyways, perhaps we'd do well to remove it. Ravensbrew (talk) 00:33, 27 October 2015 (UTC)
I support removing the "inflaton" business, might as well just mumble "because quantum". As for non-inertial: the accelerating expansion with a positive cosmological constant is as inertial as the decelerating expansion without, isn't it? It should be worded better but the idea is right and does belong in the article. Yes, this is very confusing to "Wikipedia's general target audience", but the current state of affairs is extremely confusing, so very confusing would be an improvement. -- (talk) 00:55, 4 October 2016 (UTC)

Pornographic diagram should be removed[edit]

The sexually suggestive "redshifting" diagram should be removed as I don't believe unnecessary eroticism should be included in an encyclopedia entry on such a scholarly and decidedly non-erotic topic — Preceding unsigned comment added by (talk) 06:25, 3 July 2015 (UTC)

?? Can you say which image precisely you mean, because nothing in the article seems sexual to me. Dragons flight (talk) 08:22, 3 July 2015 (UTC)
It must be what can also be interpreted as a tilted glass, full of - I don't know what.... ;-) But seriously, I have a big problem with this picture: the scale. Again, it is yet another choice of coordinates, very confusing. I just can't quite figure out neither the time nor the radius scales.Hilmer B (talk) 10:39, 3 July 2015 (UTC)

misconceptions in intro[edit]

The following paragraph in the intro falls into some misconceptions:

While special relativity constrains objects in the Universe from moving faster than light with respect to each other when they are in a local, dynamical relationship, it places no theoretical constraint on the relative motion between two objects that are globally separated and out of causal contact. It is thus possible for two objects to become separated in space by more than the distance light could have travelled, which means that, if the expansion remains constant, the two objects will never come into causal contact. For example, galaxies that are more than approximately 4.5 gigaparsecs (14.7 billion light-years) away from us are expanding away from us faster than light. We can still see such objects because the Universe in the past was expanding more slowly than it is today, so the ancient light being received from these objects is still able to reach us, though if the expansion continues unabated, there will never come a time that we will see the light from such objects being produced today (on a so-called "space-like slice of spacetime") and vice versa because space itself is expanding between Earth and the source faster than any light can be exchanged.

This 14.7 Gly distance is the Hubble radius, the distance at which recession speed > speed of light. However, the event horizon is a little larger, about 16 Gly. Galaxies in between those two distances are moving away from us faster than the speed of light, but the light they emit today will eventually reach us. --Amble (talk) 18:05, 27 August 2015 (UTC)

The first sentence is misleading because it implies that the important distinction is whether the objects can interact with each other ("dynamical relationship") or not ("out of causal contact"). This isn't the case; SR still works locally even without any interactions, and an object in causal contact with us can have a recession speed > c. Then "separated in space by more than the distance light could have travelled" refers to the past light cone, which is not the same as the Hubble radius or the event horizon. --Amble (talk) 19:02, 27 August 2015 (UTC)

Bill Nye for National Science Foundation[edit]

Expanding Universe by Bill Nye for National Science Foundation

Suggested file to add to this article. — Cirt (talk) 17:01, 6 October 2015 (UTC)

Pedagogical clarification, as per last line of introductory section[edit]

Hello editors. This is not an attempt at trolling, but difficulty in making sense of this idea in terms that are easily comprehensible to those who don't already understand it. Since difficulties in communicating this hard material were noted in the article's introduction, I thought perhaps this note would be appropriate.

If I comprehend what is described here - and I'm not at all sure that I do - the point is that the expansion of "space" is a feature of changing measurable distances. So, when we say that "space" came into being after the big bang, we mean that measurable objects came into being, after which the term "space" denoted their relative placement to one another? In other words, that the term "space" denotes measurable distances, and nothing else?

Odd question, I know. But it goes to a conceptual or predictive question: on this conception of space-time, is it imagineable that our expanding universe could encounter, let's say, another expanding universe coming from the opposite direction, which we would only suddenly become aware of once light waves could travel appropriate distances, and so on? That is, can there be "space" outside of "space" as we measure it? Or is the creation of "space" a more metaphysical sort of change, in which some "thing" came into being where there could have been nothing at all before?

In other words "if 'space' came into being, can there be anything outside of it thus understood?" I'm struggling to make sense of how exactly metric expansion should be taken - as a description of measurement, or as a claim about being.

I wouldn't ask this, except the pedagogical concerns noted suggest that it might be a plausible topic for consideration. This is an intrinsically hard topic to convey, I understand - I'm a university educator myself, in a very different field - but I thought I'd raise the question.

My thanks for reading an over-long question, in any case.2601:1C0:C001:9D43:DC75:4BE9:20A3:1BE3 (talk) 05:33, 12 October 2015 (UTC)

hey, i will have a bash at this! you are sort of asking two questions... Q1 is there an "area" into which our universe expands? ok so we have no need for an "outside" area into which our "space" is expanding... the expansion of an infinite universe can happen within (for want of a better word) the already infinite universe! the maths are pretty complex (as is all physics really) but i am assured that this is probably the case (barring really exotic answers we dont have yet of course... ;) ) Q2 is it possible there are other universes (A2a YES!) that may be expanding into the same "area" as our universe (A2b YES ALSO!) and can we potentially discover/detect them... (A2c, right this is an annoying answer but i think it's the best you will get at the moment in physics...) who knows... sorry dude, but if a universe was operating on a dif set of physical laws it maybe impossible for us to detect it, however if a universe was using similar or the same physical laws then yes in theory we could detect or interact with it. (talk) 18:42, 9 March 2016 (UTC)

Georges Lemaître censored ?[edit]

Georges Lemaître proposed the theory of the expansion of the universe, widely misattributed to Hubble 1927. Lemaître is also credited with proposing a theory for the origin of the universe that would later be called the "big bang." -- (talk) 22:13, 5 November 2015 (UTC)

Virtual subluminal (sub-lightspeed) sphere[edit]

The Universe is acceleratively expanding. The whole Universe recedes from any arbitrary observer, faster than the speed of light in the void (ultralightspeed expansion), except from an enormous imaginary sphere which surrounds each beholder. The region inside that imaginary unique and personal sphere doesn't recede at an ultralightspeed rate - on average - in the eye of each beholder. Quantum information cannot travel faster than the speed of light in the void. Only underlightspeed expansion allows the transmision of quantum information. So our arbitrary observer cannot receive information from any specific location outside his "virtual sub-lightspeed sphere", but only potential information (random quantum jittering at the boundary of the sphere that causes virtual particles to become actual for our beholder) from the boundaries of his sub-lightspeed imaginary sphere. All possible sub-lightspeed imaginary spheres of all possible observers shrink due to the accelerative expansion of space. During that sphere-shrinking, the potential radiation increases until it reaches Big Bang energy levels when each virtual sphere becomes a singularity point. We call these events Big Bangs. Due to quantum-tunneling, particles disperse all over any virtual sub-lightspeed sphere, so not only dilated low energy photons are attributed.

this is the mainstream theory that explains the unknown part of the Cosmic Background Radiation — Preceding unsigned comment added by 2A02:587:410C:5E00:C8DD:F971:F636:AB2F (talk) 00:52, 1 March 2016 (UTC)

Update: Expansion rate higher than expected[edit]

New paper:

Cheers, BatteryIncluded (talk) 13:57, 3 June 2016 (UTC)

@BatteryIncluded: Just noticed above post - already added following to main article => In June 2016, NASA and ESA scientists reported that the universe was found to be expanding 5% to 9% faster than thought earlier, based on studies using the Hubble Space Telescope.[1] - *entirely* ok with me to rv/rm/mv/ce edit of course - iac - Enjoy! :) Drbogdan (talk) 15:08, 3 June 2016 (UTC)


  1. ^ Radford, Tim (3 June 2016). "Universe is expanding up to 9% faster than we thought, say scientists". The Guardian. Retrieved 3 June 2016. 

Milne model[edit]

1st para of the last section: Chief among the underlying principles that result in models including metric expansion as a feature are: * the Cosmological Principle which demands that the universe looks the same way in all directions (isotropic) and has roughly the same smooth mixture of material (homogeneous). * the Copernican Principle which demands that no place in the universe is preferred (that is, the universe has no "starting point").

2nd last para: Until that time, it was based purely on an assumption that the universe did not behave as one with the Milky Way sitting at the middle of a fixed-metric with a universal explosion of galaxies in all directions (as seen in, for example, an early model proposed by Milne). Yet before this evidence, many rejected the Milne viewpoint based on the mediocrity principle.

Well, as the article linked explains, the Milne model satisfies the cosmological principle. So what are we talking about here?

The article is locked, but can someone at least put challenge tags around this stuff? -- (talk) 00:30, 4 October 2016 (UTC)


Due to the non-intuitive nature of the subject and what has been described by some as "careless" choices of wording, certain descriptions of the metric expansion of space and the misconceptions to which such descriptions can lead are an ongoing subject of discussion in the realm of pedagogy and communication of scientific concepts.[2][3][4][5]

Amen brothers and sisters! Can we move this closer to the top? -- (talk) 00:44, 4 October 2016 (UTC)