Big Bounce

For other uses, see The Big Bounce (disambiguation).

The Big Bounce is a theoretical scientific model of the formation of the known universe. It is implied by the cyclic model or oscillatory universe interpretation of the Big Bang where the first cosmological event was the result of the collapse of a previous universe.

Expansion and contraction

According to some oscillatory universe theorists, the Big Bang was simply the beginning of a period of expansion that followed a period of contraction. In this view, one could talk of a Big Crunch followed by a Big Bang, or more simply, a Big Bounce. This suggests that we could be living at any point in an infinite sequence of universes, or conversely the current universe could be the very first iteration. However, if the condition of the interval phase "between bounces", considered the 'hypothesis of the primeval atom', is taken into full contingency such enumeration may be meaningless because that condition could represent a singularity in time at each instance, if such perpetual return was absolute and undifferentiated.

The main idea behind the quantum theory of a Big Bounce is that, as density approaches infinity, the behavior of the quantum foam changes. All the so-called fundamental physical constants, including the speed of light in a vacuum, were not so constant during the Big Crunch, especially in the interval stretching 10⁻⁴³ seconds before and after the point of inflection. (One unit of Planck time is about 10⁻⁴³ seconds.)

If the fundamental physical constants were determined in a quantum-mechanical manner during the Big Crunch, then their apparently inexplicable values in this universe would not be so surprising, it being understood here that a universe is that which exists between a Big Bang and its Big Crunch.

Recent developments in the theory

Martin Bojowald, an assistant professor of physics at Pennsylvania State University, published a study in July 2007 detailing work somewhat related to loop quantum gravity that claimed to mathematically solve the time before the Big Bang, which would give new weight to the oscillatory universe and Big Bounce theories.

One of the main problems with the Big Bang theory is that at the moment of the Big Bang, there is a singularity of zero volume and infinite energy. This is normally interpreted as the end of the physics as we know it; in this case, of the theory of general relativity. This is why one expects quantum effects to become important and avoid the singularity.

However, research in loop quantum cosmology purported to show that a previously existing universe collapsed, not to the point of singularity, but to a point before that where the quantum effects of gravity become so strongly repulsive that the universe rebounds back out, forming a new branch. Throughout this collapse and bounce, the evolution is unitary.

Bojowald also claims that some properties of the universe that collapsed to form ours can also be determined. Some properties of the prior universe are not determinable however due to some kind of uncertainty principle.

This work is still in its early stages and very speculative. Some extensions by further scientists have been published in Physical Review Letters.

In 2003, Peter Lynds has put forward a new cosmology model in which time is cyclic. In his theory our Universe will eventually stop expanding and then contract. Before becoming a singularity, as one would expect from Hawking's black hole theory, the Universe would bounce. Lynds claims that a singularity would violate the second law of thermodynamics and this stops the Universe from being bounded by singularities. The Big Crunch would be avoided with a new Big Bang. Lynds suggests the exact history of the Universe would be repeated in each cycle in an eternal recurrence. Some critics argue that while the Universe may be cyclic, the histories would all be variants.^{[citation needed]} Lynds theory has been dismissed by mainstream physicists for the lack of a mathematical model behind its philosophical considerations.

See also

• Abhay Ashtekar
• Anthropic principle
• Martin Bojowald
• John Archibald Wheeler
• Loop quantum cosmology
• Loop quantum gravity
• Supernova
• Astronomy portal
• Space portal
• Solar System portal

Further reading

• Magueijo, João (2003). Faster than the Speed of Light: the Story of a Scientific Speculation. Cambridge, MA: Perseus Publishing. ISBN 0738205257. 
• Bojowald, Martin (2008). "Follow the Bouncing Universe". Scientific American 299 (October 2008): 44–51. PMID 18847084. 

External links

• Dark Matter, Antimatter, and Time-Symmetry, Trevor Pitts, 1999
• Penn State Researchers Look Beyond The Birth Of The Universe (Penn State) May 12, 2006
• What Happened Before the Big Bang? (Penn State) July 1, 2007
• From big bang to big bounce (Pen State) NewScientist December 13, 2008
• SpringerLink - Gravitation and Cosmology, Volume 16, Number 4