Editing Zero-point energy (section)

== Speculated involvement in other phenomena ==

=== Dark energy ===
{{Main|Dark energy}}
{{unsolved|physics|Why does the large zero-point energy of the [[vacuum]] not cause a large cosmological constant? What cancels it out?{{sfnp|Rugh|Zinkernagel|2002}}<ref name=scientificamerican0588-106 />{{sfnp|Battersby|2016}}}}
In the late 1990s it was discovered that very distant [[supernova]]e were dimmer than expected suggesting that the universe's expansion was accelerating rather than slowing down.{{sfnp|Riess et al.|1998}}{{sfnp|Perlmutter et al.|1998}} This revived discussion that Einstein's cosmological constant, long disregarded by physicists as being equal to zero, was in fact some small positive value. This would indicate empty space exerted some form of [[Negative energy|negative pressure or energy]].

There is no natural candidate for what might cause what has been called dark energy but the current best guess is that it is the zero-point energy of the vacuum, but this guess is known to be off by 120 [[order of magnitude|orders of magnitude]].<ref>{{cite magazine|last1=Clark|first1=Stuart|title=The Universe is Flat as a Pancake|magazine=New Scientist|date=2016|volume=232|issue=3097|page=35|url=https://archive.org/details/NewScientistOctober29/page/n35/mode/2up}}</ref>

The [[European Space Agency|European Space Agency's]] [[Euclid (spacecraft)|Euclid telescope]], launched on 1 July 2023, will map galaxies up to 10 billion light years away.<ref>{{Cite news |date=2023-07-01 |title=The Dark Universe Is Waiting. What Will the Euclid Telescope Reveal? |work=The New York Times |language=en |url=https://www.nytimes.com/2023/07/01/science/spacex-euclid-launch.html |access-date=2023-08-23 |last1=Miller |first1=Katrina }}</ref> By seeing how dark energy influences their arrangement and shape, the mission will allow scientists to see if the strength of dark energy has changed. If dark energy is found to vary throughout time it would indicate it is due to [[Quintessence (physics)|quintessence]], where observed acceleration is due to the energy of a [[scalar field]], rather than the cosmological constant. No evidence of quintessence is yet available, but it has not been ruled out either. It generally predicts a slightly slower acceleration of the expansion of the universe than the cosmological constant. Some scientists think that the best evidence for quintessence would come from violations of Einstein's [[equivalence principle]] and [[equivalence principle#Tests of the Einstein equivalence principle|variation of the fundamental constants]] in space or time.<ref name="Carroll1998">{{cite journal|last1=Carroll|first1=Sean M.|title=Quintessence and the Rest of the World: Suppressing Long-Range Interactions|journal=Physical Review Letters|volume=81|issue=15|year=1998|pages=3067–3070|issn=0031-9007|doi=10.1103/PhysRevLett.81.3067|arxiv = astro-ph/9806099 |bibcode = 1998PhRvL..81.3067C |s2cid=14539052|url=https://cds.cern.ch/record/356711/files/9806099.pdf}}</ref> Scalar fields are predicted by the ''[[Standard Model]] of particle physics'' and [[string theory]], but an analogous problem to the cosmological constant problem (or the problem of constructing models of [[cosmological inflation]]) occurs: [[renormalization]] theory predicts that scalar fields should acquire large masses again due to zero-point energy.

=== Cosmic inflation ===
{{Main|Inflation (cosmology)}}
{{unsolved|physics|Why does the observable universe have more matter than antimatter?}}

[[Cosmic inflation]] is phase of accelerated [[cosmic expansion]] just after the Big Bang. It explains the origin of the [[Observable universe#Large-scale structure|large-scale structure of the cosmos]]. It is believed [[quantum vacuum fluctuations]] caused by zero-point energy arising in the microscopic inflationary period, later became magnified to a cosmic size, becoming the gravitational seeds for galaxies and structure in the Universe (see [[galaxy formation and evolution]] and [[structure formation]]).<ref>Tyson, Neil deGrasse and Donald Goldsmith (2004), ''Origins: Fourteen Billion Years of Cosmic Evolution'', W. W. Norton & Company, pp. 84–85.</ref> Many physicists also believe that inflation explains why the Universe appears to be the same in all directions ([[isotropic]]), why the [[cosmic microwave background]] radiation is distributed evenly, why the Universe is flat, and why no [[magnetic monopole]]s have been observed.

The mechanism for inflation is unclear, it is similar in effect to dark energy but is a far more energetic and short lived process. As with dark energy the best explanation is some form of vacuum energy arising from quantum fluctuations. It may be that inflation caused [[baryogenesis]], the hypothetical physical processes that produced an [[symmetry|asymmetry]] (imbalance) between [[baryon]]s and antibaryons produced in the [[Big Bang|very early universe]], but this is far from certain.

=== Cosmology ===
[[Paul S. Wesson]] examined the cosmological implications of assuming that zero-point energy is real.<ref>Wesson, Paul S. "Cosmological constraints on the zero-point electromagnetic field." Astrophysical Journal, Part 1 (ISSN 0004-637X), vol. 378, Sept. 10, 1991, p. 466-470. Research supported by NSERC. 378 (1991): 466-470.</ref> Among numerous difficulties, [[general relativity]] requires that such energy not gravitate, so it cannot be similar to electromagnetic radiation.