Editing Cosmological constant (section)

=== Footnotes ===
{{reflist|30em|refs=
<ref name="CC Definition">It may well be that dark energy is explained by a static cosmological constant, or that this mysterious energy is not constant at all and has changed over time, as in the case with quintessence, see for example:
* "Physics invites the idea that space contains energy whose gravitational effect approximates that of Einstein's cosmological constant, Λ; nowadays the concept is termed dark energy or quintessence." {{harvp|Peebles|Ratra|2003|p=1}}
* "It would then appear that the cosmological fluid is dominated by some sort of fantastic energy density, which has negative pressure, and has just begun to play an important role today. No convincing theory has yet been constructed to explain this state of affairs, although cosmological models based on a dark energy component, such as the cosmological constant ({{math|Λ}}) or quintessence (Q), are leading candidates." {{harvp|Caldwell|2002|p=2}}
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<ref name="Rugh 2001 3">{{harvp|Rugh|Zinkernagel|2001|p=3}}</ref>
<ref name="Λ = 0?">On the Cosmological Constant being thought to have zero value see for example:
* "Since the cosmological upper bound on {{abs|{{angle bracket|''ρ''}} + ''λ''/8''πG''}} was vastly less than any value expected from particle theory, most particle theorists simply assumed that for some unknown reason this quantity was zero." {{harvp|Weinberg|1989|p=3}}
* "An epochal astronomical discovery would be to establish by convincing observation that Λ is nonzero." {{harvp|Carroll|Press|Turner|1992|p=500}}
* "Before 1998, there was no direct astronomical evidence for Λ and the observational upper bound was so strong (Λ&nbsp;<&nbsp;10<sup>−120</sup>&nbsp;Planck units) that many particle physicists suspected that some fundamental principle must force its value to be precisely zero." {{harvp|Barrow|Shaw|2011|p=1}}
* "The only other natural value is Λ&nbsp;=&nbsp;0. If Λ really is tiny but not zero, it adds a most stimulating though enigmatic clue to physics to be discovered." {{harvp|Peebles|Ratra|2003|p=333}}
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<ref name="1998 Discovery">See for example:
* "This is the independent result of two teams. [[Supernova Cosmology Project]] ({{harvp|Perlmutter et al.|1999}}; also see {{harvp|Perlmutter et al.|1998}}) and the [[High-Z Supernova Search Team]] ({{harvp|Riess et al.|1998}}; also see {{harvp|Schmidt et al.|1998}})" {{harvp|Weinberg|2015|p=376}}
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<ref name="Biggest Blunder">There is some debate over whether Einstein labelled the cosmological constant his "biggest blunder", with all references being traced back to a single person: [[George Gamow]]. (See {{harvs|txt|last1=Gamow|year1=1956|year2=1970}}.) For example:
* "Astrophysicist and author Mario Livio can find no documentation that puts those words into Einstein's mouth (or, for that matter, his pen). Instead, all references eventually lead back to one man—physicist George Gamow—who reported Einstein's use of the phrase in two sources: His posthumously published autobiography ''My World Line'' (1970) and a ''Scientific American'' article from September&nbsp;1956." {{harvp|Rosen|2013}}
* " We also find it quite plausible that Einstein made such a statement to Gamow in particular. We conclude that there is little doubt that Einstein came to view the introduction of the cosmological constant a serious error, and that it is very plausible that he labelled the term his "biggest blunder" on at least one occasion". {{harvp|O'Raifeartaigh|Mitton|2018|p=1}}
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<ref name="CC Problem">See for example:
* "This gives an answer about 120&nbsp;orders of magnitude higher than the upper limits on Λ set by cosmological observations. This is probably the worst theoretical prediction in the history of physics!" {{harvp|Hobson|Efstathiou|Lasenby|2006|p=187}}
* "This, as we will see later, is approximately 120&nbsp;orders of magnitude larger than what is allowed by observation." {{harvp|Carroll|Press|Turner|1992|p=503}}
* "Theoretical expectations for the cosmological constant exceed observational limits by some 120&nbsp;orders of magnitude." {{harvp|Weinberg|1989|p=1}}</ref>
<ref name="CC Problem 3">See for example:
* "the vacuum holds the key to a full understanding of nature" {{harvp|Davies|1985|p=104}}
* "The theoretical problem of explaining the cosmological constant is one of the greatest challenges of theoretical physics. It is most likely that we require a fully developed theory of quantum gravity (perhaps superstring theory) before we can understand Λ." {{harvp|Hobson|Efstathiou|Lasenby|2006|p=188}}</ref>
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