Zero-energy universe

The zero-energy universe hypothesis proposes that the total amount of energy in the universe is exactly zero: its amount of positive energy in the form of matter is exactly canceled out by its negative energy in the form of gravity.<ref>"A Universe From Nothing lecture by Lawrence Krauss at AAI". YouTube. 2009. Archived from the original on 2021-12-15. Retrieved 17 October 2011.</ref> Some physicists, such as Lawrence Krauss, Stephen Hawking or Alexander Vilenkin, call or called this state "a universe from nothingness", although the zero-energy universe model requires both a matter field with positive energy and a gravitational field with negative energy to exist.<ref name="Quantum">Isham, Christopher (14 July 1994). Quantum Cosmology and the Origin of the Universe (Speech). Lecture presented at the conference “Cosmos and Creation. Cambridge University.</ref> The hypothesis is broadly discussed in popular sources.<ref name="Krauss2012">Lawrence M. Krauss (2012). A Universe from Nothing: Why There Is Something Rather Than Nothing. Simon and Schuster. pp. 150-151. ISBN 978-1-4516-2445-8.</ref><ref name=Tryon1973>Edward P. Tryon, "Is the Universe a Vacuum Fluctuation?", Nature, vol. 246, p.396–397, 1973.</ref><ref>Berkeley Lab, Smoot Group - http://aether.lbl.gov - Inflation for Beginners, JOHN GRIBBIN archived, 2014</ref> Other cancellation examples include the expected symmetric prevalence of right- and left-handed angular momenta of objects ("spin" in the common sense), the observed flatness of the universe, the equal prevalence of positive and negative charges, opposing particle spin in quantum mechanics, as well as the crests and troughs of electromagnetic waves, among other possible examples in nature.

History

During World War II, Pascual Jordan first suggested that since the positive energy of a star's mass and the negative energy of its gravitational field together may have zero total energy, conservation of energy would not prevent a star being created by a quantum transition of the vacuum. George Gamow recounted putting this idea to Albert Einstein: "Einstein stopped in his tracks and, since we were crossing a street, several cars had to stop to avoid running us down".<ref>Beyond Einstein: The Cosmic Quest for the Theory of the Universe - Michio Kaku, Jennifer Trainer Thompson - Oxford University Press, 1997 - p189</ref> Elaboration of the concept was slow, with the first notable calculation being performed by Richard Feynman in 1962.<ref name=Berman2009>Berman, Marcelo Samuel (2009). "On the Zero-Energy Universe". International Journal of Theoretical Physics. 48 (11): 3278–3286. arXiv:gr-qc/0605063. Bibcode:2009IJTP...48.3278B. doi:10.1007/s10773-009-0125-8. S2CID 119482227.</ref> The first known publication on the topic was in 1973, when Edward Tryon proposed in the journal Nature that the universe emerged from a large-scale quantum fluctuation of vacuum energy, resulting in its positive mass-energy being exactly balanced by its negative gravitational potential energy.<ref name=Tryon1973/> In the subsequent decades, development of the concept was constantly plagued by the dependence of the calculated masses on the selection of the coordinate systems. In particular, a problem arises due to energy associated with coordinate systems co-rotating with the entire universe.<ref name=Berman2009/> A first constraint was derived in 1987 when Alan Guth published a proof of gravitational energy being negative.<ref>Alan Guth, in his book The Inflationary Universe, (ISBN 0-224-04448-6) Appendix A.</ref> The question of the mechanism permitting generation of both positive and negative energy from null initial solution was not understood, and an ad hoc solution with cyclic time was proposed by Stephen Hawking in 1988.<ref>Stephen Hawking, A Brief History of Time, p. 129.</ref><ref>"We might decide that there wasn't any singularity. The point is that the raw material doesn't really have to come from anywhere. When you have strong gravitational fields, they can create matter. It may be that there aren't really any quantities which are constant in time in the universe. The quantity of matter is not constant, because matter can be created or destroyed. But we might say that the energy of the universe would be constant, because when you create matter, you need to use energy. And in a sense the energy of the universe is constant; it is a constant whose value is zero. The positive energy of the matter is exactly balanced by the negative energy of the gravitational field. So the universe can start off with zero energy and still create matter. Obviously, the universe starts off at a certain time. Now you can ask: what sets the universe off. There doesn't really have to be any beginning to the universe. It might be that space and time together are like the surface of the Earth, but with two more dimensions, with degrees of latitude playing the role of time." -- Stephen Hawking, "If There's an Edge to the Universe, There Must Be a God" (interview), in Renée Weber, Dialogues With Scientists and Sages: The Search for Unity, 1986. (Also partially reprinted in "God as the Edge of the Universe", in The Scientist, Vol. 1, No. 7, February 23, 1987, p. 15.)</ref>

In 1994, development of the theory resumed<ref>Xulu, S. S. (2000). "Total Energy of the Bianchi Type I Universes". Int. J. Theor. Phys. 39 (4): 1153–1161. arXiv:gr-qc/9910015. Bibcode:2000IJTP...39.1153X. doi:10.1023/A:1003670928681. S2CID 15413640.</ref> following the publication of a work by Nathan Rosen,<ref>Rosen, Nathan (March 1994). "The energy of the universe". General Relativity and Gravitation. 26 (3): 319–321. Bibcode:1994GReGr..26..319R. doi:10.1007/BF02108013. S2CID 121139141.</ref> in which Rosen described a special case of closed universe. In 1995, J.V. Johri demonstrated that the total energy of Rosen's universe is zero in any universe compliant with a Friedmann–Lemaître–Robertson–Walker metric, and proposed a mechanism of inflation-driven generation of matter in a young universe.<ref>Johri, V. B.; Kalligas, D.; Singh, G. P.; Everitt, C. W. F. (March 1995). "Gravitational energy in the expanding universe". General Relativity and Gravitation. 27 (3): 313–318. Bibcode:1995GReGr..27..313J. doi:10.1007/BF02109127. S2CID 120110466.</ref> The zero energy solution for Minkowski space representing an observable universe, was provided in 2009.<ref name=Berman2009/>

In his book Brief Answers to the Big Questions, Hawking explains:

Experimental constraints

Experimental proof for the observable universe being a "zero-energy universe" is currently inconclusive. Gravitational energy from visible matter accounts for 26–37% of the observed total mass–energy density.<ref>Shankar, Karthik H. (2020). "Eternally oscillating zero energy universe". General Relativity and Gravitation. 52 (2): 23. arXiv:1807.10381. Bibcode:2020GReGr..52...23S. doi:10.1007/s10714-020-02671-5. S2CID 119208193.</ref> Therefore, to fit the concept of a "zero-energy universe" to the observed universe, other negative energy reservoirs besides gravity from baryonic matter are necessary. These reservoirs are frequently assumed to be dark matter.<ref>Popławski, Nikodem J. (2014). "The energy and momentum of the Universe". Classical and Quantum Gravity. 31 (6): 065005. arXiv:1305.6977. Bibcode:2014CQGra..31f5005P. doi:10.1088/0264-9381/31/6/065005. S2CID 118593046.</ref>

See also

• A Universe from Nothing
• False vacuum
• List of cosmology paradoxes – List of statements that appear to contradict themselves