Editing Zero-point energy (section)

== Alternative theories ==
There has been a long debate<ref>{{cite book|last1=Enz|first1=Charles P.|editor1-last=Enz|editor1-first=C. P.|editor2-last=Mehra|editor2-first=J.|title=Physical Reality and Mathematical Description Is the Zero-Point Energy Real?|date=1974|publisher=D. Reidel Publishing Company|location=Dordrecht|isbn=978-94-010-2274-3|pages=124–132|doi=10.1007/978-94-010-2274-3|s2cid=118779716 }}</ref> over the question of whether zero-point fluctuations of quantized vacuum fields are "real" i.e. do they have physical effects that cannot be interpreted by an equally valid alternative theory? [[Julian Schwinger|Schwinger]], in particular, attempted to formulate QED without reference to zero-point fluctuations via his "source theory".<ref>See {{harvs|txt|last1=Schwinger|year1=1998a|year2=1998b|year3=1998c}}.</ref> From such an approach it is possible to derive the Casimir Effect without reference to a fluctuating field. Such a derivation was first given by Schwinger (1975)<ref>{{cite journal|last1=Schwinger|first1=Julian|title=Casimir effect in source theory|journal=Letters in Mathematical Physics|date=1975|volume=1|issue=1|pages=43–47|doi=10.1007/BF00405585|bibcode=1975LMaPh...1...43S|s2cid=126297065}}</ref> for a scalar field, and then generalized to the electromagnetic case by Schwinger, DeRaad, and Milton (1978).<ref>{{cite journal|last1=Schwinger|first1=Julian|last2=DeRaad|first2=Lester L.|last3=Milton|first3=Kimball A.|title=Casimir effect in dielectrics|journal=Annals of Physics|date=1978|volume=115|issue=1|pages=1–23|doi=10.1016/0003-4916(78)90172-0|bibcode= 1978AnPhy.115....1S}}</ref> in which they state "the vacuum is regarded as truly a state with all physical properties equal to zero". [[Robert Jaffe (physicist)|Jaffe]] (2005)<ref name=Jaffe2005>{{cite journal|last=Jaffe |first=R. L.|year=2005|title=Casimir effect and the quantum vacuum|journal=[[Physical Review D]]|volume=72 |issue=2 |page=021301|arxiv= hep-th/0503158|bibcode= 2005PhRvD..72b1301J|doi=10.1103/PhysRevD.72.021301|s2cid=13171179}}</ref> has highlighted a similar approach in deriving the Casimir effect stating "the concept of zero-point fluctuations is a heuristic and calculational aid in the description of the Casimir effect, but not a necessity in QED."

[[Peter W. Milonni|Milonni]] has shown the necessity of the vacuum field for the formal consistency of QED.{{sfnp|Milonni|1994|p=48}} Modern physics does not know any better way to construct gauge-invariant, renormalizable theories than with zero-point energy and they would seem to be a necessity for any attempt at a [[Grand Unified Theory|unified theory]].{{sfnp|Greiner|Müller|Rafelski|2012|p=20}}
Nevertheless, as pointed out by Jaffe, "no
known phenomenon, including the Casimir effect, demonstrates that zero point energies are “real”"<ref name=Jaffe2005/>