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      • 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. 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. The hypothesis is broadly discussed in popular sources. 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". Elaboration of the concept was slow, with the first notable calculation being performed by Richard Feynman in 1962. 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. 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. A first constraint was derived in 1987 when Alan Guth published a proof of gravitational energy being negative. 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.
      In 1994, development of the theory resumed following the publication of a work by Nathan Rosen, 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. The zero energy solution for Minkowski space representing an observable universe, was provided in 2009.
      In his book Brief Answers to the Big Questions, Hawking explains:

      The laws of physics demand the existence of something called 'negative energy'.To help you get your head around this weird but crucial concept, let me draw on a simple analogy. Imagine a man wants to build a hill on a flat piece of land. The hill will represent the universe. To make this hill he digs a hole in the ground and uses that soil to dig his hill. But of course he's not just making a hill—he's also making a hole, in effect a negative version of the hill. The stuff that was in the hole has now become the hill, so it all perfectly balances out. This is the principle behind what happened at the beginning of the universe. When the Big Bang produced a massive amount of positive energy, it simultaneously produced the same amount of negative energy. In this way, the positive and the negative add up to zero, always. It's another law of nature. So where is all this negative energy today? It's in the third ingredient in our cosmic cookbook: it's in space. This may sound odd, but according to the laws of nature concerning gravity and motion—laws that are among the oldest in science—space itself is a vast store of negative energy. Enough to ensure that everything adds up to zero.


      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. 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.


      See also


      A Universe from Nothing
      False vacuum
      Heat death of the universe
      List of cosmology paradoxes – List of statements that appear to contradict themselves
      Ultimate fate of the universe


      References

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    Artikel Terkait "zero energy universe"

    Zero-Energy Universe: Stephen Hawking Explains - Physics Forums

    16 Mar 2018 · The zero-energy universe only applies to a closed universe, not a flat or open universe. It's based upon the Hamiltonian formulation of General Relativity, which contains a sort of potential energy (in the typical formulation of GR, there is no potential energy).

    Zero-Energy Universe Hypothesis: Questions & Answers

    25 Agu 2014 · If the Zero-Energy Universe Hypothesis is correct, it means that the universe will continue to expand and eventually reach a state of maximum entropy, known as the heat death of the universe. This would result in a universe with no energy or activity, effectively leading to the end of all life and processes as we know them.

    Zero-Energy Universe: Reliable Source? - Physics Forums

    27 Mei 2020 · Abstract of Ref. 5 (by the way, 47 years old) from wikipedia page "zero-energy universe" cites: The author proposes a big bang model in which our Universe is a fluctuation of the vacuum, in the sense of quantum field theory. The model predicts a Universe which is homogeneous, isotropic and closed, and consists equally of matter and anti-matter.

    Understanding the Zero Energy Principle of the Universe

    25 Apr 2012 · What the zero-energy-universe-cosmologists are trying to establish is a theory that explains how the universe came out of nothing. One problem here is that "something out of nothing" is a term that makes it sound nice in pop-science books.

    Is the total energy of the Universe Zero? - Physics Forums

    27 Des 2008 · In summary, the conversation discusses the concept of the Universe appearing out of nothing and the idea that all energy in the Universe cancels out to make nothing. The question is whether or not this is correct and the conversation also touches on the idea of a cause for every effect and the relationship between energy and matter in the Universe.

    What constitutes negative and positive energy - Physics Forums

    26 Jan 2016 · I'm a little confused over what constitutes negative and positive energy. I've heard it said that we have a zero energy universe because the mass of the galaxies, etc. counts as positive energy which is exactly balanced out by gravity, or the gravitational potential, which counts as negative energy. Ok, that's understandable.

    Unraveling the Mystery of Total Energy in the Universe - Physics …

    14 Agu 2004 · In summary, there is debate among scientists about whether the total energy of the universe is exactly zero or slightly more or less. Some scientists have proposed the concept of "zero energy" to explain the existence of the universe, while others argue that the third law of Thermodynamics suggests a constant and unchanging total energy.

    Is Gravitational Energy Truly Negative in a Zero-Energy Universe?

    05 Mar 2013 · Why choose a convention where gravitational energy is negative? As with all potential energies, only differences in gravitational potential energy matter for most physical purposes, and the choice of zero point is arbitrary.

    Does Zero Net Energy equal Zero Energy? - Physics Forums

    07 Sep 2015 · It seems that some of the new "free lunch" cosmological models promote the idea that if the universe has zero net energy, zero energy was required to create it. However, a closed system can have tremendous potential energy but zero net energy, so the idea seems questionable to me, even if the positive and negative energies add up to precisely zero.

    Is the Energy of the Universe Really Zero? - Physics Forums

    07 Mei 2007 · Richard Feynman mused over the notion of a zero energy universe (at page 10 - in his book on gravitation). Says Feynman "It is exciting to think that it cost nothiing to create a new particle since we can create it at the center of the universe where it will have a negative gravitaional energy equal to mc^2"