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Either the Universe will continue in its present form forever, or it will cease to exist in its present form at some time.
Many religions have postulated an end to the Universe, for example as part of an Apocalypse ordained by God; see the article on eschatology for more discussion of these issues. This article is about scientific theories of the end of the Universe.
Scientific ideas of the end of the Universe
Until fairly recent times, even the scientific view of the Universe was one of eternal and unchanging existence. After Edwin Hubble's discovery of an expanding Universe, suddenly the notion of a start and, possibly, an end, was the subject of scientific investigation.
Theories can be divided into four major groups:
The first group is not discussed in this article, since it negates the very concept of an "ending of the Universe". In these theories, some kind of meaningful activity can last forever.
All theories must come to terms with general relativity, which provides a common background for cosmological speculation. Most of these theories are solutions of GR equations, only changing parameters like average density, cosmological constant, etc.
Infinite time, but finite lifespan
In an open Universe, General Relativity shows that the Universe can exist indefinitely in the future, but will settle down into a state where life as we know it will cease to exist; for a possible timeline based on current physical theories, see 1 E19 s and more.
In 2003, New Scientist magazine reported a preprint by Robert R. Caldwell, Marc Kamionkowski and Nevin N. Weinberg which puts forward the hypothesis that the end of the Universe may occur as a "Big Rip", which will shred the physical structure of the Universe.
In this model, a cosmological constant causes the Universe's rate of expansion to accelerate. Taken to the extreme, an ever-accelerating expansion means that all physical objects in the Universe, starting with galaxies and down to individual human beings, bacteria, and grains of sand, will eventually be torn to pieces and then to elementary particles. The Universe will be then reduced to single elementary particles forever accelerating away from one another.
Finite time and lifespan
The Big Crunch theory is a symmetrical view of the life of the Universe. Just as the Big Bang started a cosmological expansion, this theory postulates that the average density of the Universe is enough to stop its expansion and begin a cosm-wide contraction.
It is unclear what the end result would be: a simple extrapolation would have all the matter and space-time in the Universe collapse into a dimensionless singularity, but at these scales quantum effects, ignored by General Relativity, should be considered. Some people use this opportunity to postulate an oscillatory Universe, that starts again to expand.
Life in a mortal Universe
Some well-known physicists have speculated that an advanced civilization could use a finite amount of energy to survive for an effectively infinite amount of time. The strategy is to have brief periods of activity, alternated by longer and longer periods of hibernation (see Dyson's eternal intelligence for more information).
The reverse is true for a civilization finding itself in the middle of the Big Crunch. Here, an effectively infinite amount of subjective time can be extracted from the finite remaining time, using the enormous energy of the Crunch to "speed up" life faster than the limit is approaching. (see Frank J. Tipler's Omega point)
Even if possible in theory, it is not clear if a practical way to use those possibilities can be developed by any civilization, as advanced as it may be.
Recent work in fields such as inflationary cosmology, string theory, and quantum mechanics has pushed the debate into an entirely distinct realm from the scenarios discussed in Dyson's and Tipler's hypotheses. Physicists such as Eric Chaisson and David Layzer have noted that an increasing "entropy gap" arises in an expanding spacetime, casting doubt on the heat death hypothesis. In conjunction with work by Ilya Prigogine on far-from-equilibrium thermodynamics, their analysis suggests that the gap itself may contribute to information and the formation of structure.
Meanwhile, physicists such as Andrei Linde, Alan Guth, Edward Harrison, and Ernest Sternglass have demonstrated that inflationary cosmology strongly suggests the presence of a multiverse, and that it would be practical even with today's knowledge for intelligent beings to de novo generate and transmit information into a distinct universe. Moreover, recent theoretical work on the unresolved quantum gravity problem and the Holographic Principle has indicated that traditional physical quantities may possibly themselves be describable in terms of exchanges of information, which in turn raises questions about the applicability of older cosmic models.
See also
External links
Recommended reading
- Fred Adams & Greg Laughlin, The Five Ages of the Universe
- John Barrow, Impossibility
- Stephen Baxter, Deep Future
- Eric Chaisson, Cosmic Evolution
- Paul Davies, The Last Three Minutes
- Alan Guth, The Inflationary Universe
- Edward Robert Harrison, Masks of the Universe: Changing Ideas on the Nature of the Cosmos
- David Layzer, Cosmogenesis
- Andrei Linde, Particle Physics and Inflationary Cosmology
- Ilya Prigogine and Isabelle Stengers, Order out of Chaos: Man's New Dialogue with Nature
- Ilya Prigogine, Is Future Given?
- Lee Smolin, The Life of the Cosmos
- Lee Smolin, Three Roads to Quantum Gravity
he:היקום המתנדנד
it:destino ultimo dell'Universo
ja:宇宙の終焉
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