Big Bounce

Big Bounce

Discussion
Ask a question about 'Big Bounce'
Start a new discussion about 'Big Bounce'
Answer questions from other users
Full Discussion Forum
 
Encyclopedia
The Big Bounce is a theoretical scientific model of the formation of the known universe
Universe
The Universe is commonly defined as the totality of everything that exists, including all matter and energy, the planets, stars, galaxies, and the contents of intergalactic space. Definitions and usage vary and similar terms include the cosmos, the world and nature...

. It is implied by the cyclic model
Cyclic model
A cyclic model is any of several cosmological models in which the universe follows infinite, self-sustaining cycles. For example, the oscillating universe theory briefly considered by Albert Einstein in 1930 theorized a universe following an eternal series of oscillations, each beginning with a...

or oscillatory universe interpretation of the Big Bang
Big Bang
The Big Bang theory is the prevailing cosmological model that explains the early development of the Universe. According to the Big Bang theory, the Universe was once in an extremely hot and dense state which expanded rapidly. This rapid expansion caused the young Universe to cool and resulted in...

 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
Metric expansion of space
The metric expansion of space is the increase of distance between distant parts of the universe with time. It is an intrinsic expansion—that is, it is defined by the relative separation of parts of the universe and not by motion "outward" into preexisting space...

 that followed a period of contraction. In this view, one could talk of a Big Crunch
Big Crunch
In physical cosmology, the Big Crunch is one possible scenario for the ultimate fate of the universe, in which the metric expansion of space eventually reverses and the universe recollapses, ultimately ending as a black hole singularity.- Overview :...

followed by a Big Bang, or more simply, a Big Bounce. This suggests that we might be living in the first of all universes, but are equally likely to be living in the 2 billionth universe (or any of an infinite other sequential universes). 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
Big Bounce
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...

 is that, as density approaches infinity, the behavior of the quantum foam
Quantum foam
Quantum foam, also referred to as spacetime foam, is a concept in quantum mechanics, devised by John Wheeler in 1955. The foam is supposed to be the foundations of the fabric of the universe. Additionally, it can be used as a qualitative description of subatomic spacetime turbulence at extremely...

changes. All the so-called fundamental physical constants, including the speed of light in a vacuum, were not so constant during the Big Crunch
Big Crunch
In physical cosmology, the Big Crunch is one possible scenario for the ultimate fate of the universe, in which the metric expansion of space eventually reverses and the universe recollapses, ultimately ending as a black hole singularity.- Overview :...

, especially in the interval stretching 10−43 seconds before and after the point of inflection. (One unit of Planck time
Planck time
In physics, the Planck time, , is the unit of time in the system of natural units known as Planck units. It is the time required for light to travel, in a vacuum, a distance of 1 Planck length...

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
Big Bang
The Big Bang theory is the prevailing cosmological model that explains the early development of the Universe. According to the Big Bang theory, the Universe was once in an extremely hot and dense state which expanded rapidly. This rapid expansion caused the young Universe to cool and resulted in...

 and its Big Crunch
Big Crunch
In physical cosmology, the Big Crunch is one possible scenario for the ultimate fate of the universe, in which the metric expansion of space eventually reverses and the universe recollapses, ultimately ending as a black hole singularity.- Overview :...

.

Recent developments in the theory


Martin Bojowald
Martin Bojowald
Martin Bojowald is a German physicist who now works on the faculty of the Penn State Physics Department, where he is a member of the Institute for Gravitation and the Cosmos. Prior to joining Penn State he spent several years at the Max-Planck Institute for Gravitational Physics in Potsdam, Germany...

, an assistant professor of physics at Pennsylvania State University
Pennsylvania State University
The Pennsylvania State University, commonly referred to as Penn State or PSU, is a public research university with campuses and facilities throughout the state of Pennsylvania, United States. Founded in 1855, the university has a threefold mission of teaching, research, and public service...

, published a study in July 2007 detailing work somewhat related to loop quantum gravity
Loop quantum gravity
Loop quantum gravity , also known as loop gravity and quantum geometry, is a proposed quantum theory of spacetime which attempts to reconcile the theories of quantum mechanics and general relativity...

 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
General relativity
General relativity or the general theory of relativity is the geometric theory of gravitation published by Albert Einstein in 1916. It is the current description of gravitation in modern physics...

. This is why one expects quantum effects to become important and avoid the singularity.

However, research in loop quantum cosmology
Loop quantum cosmology
Loop quantum cosmology is a finite, symmetry-reduced model of loop quantum gravity that predicts a quantum bridge between contracting and expanding cosmological branches...

 purported to show that a previously existing universe
Universe
The Universe is commonly defined as the totality of everything that exists, including all matter and energy, the planets, stars, galaxies, and the contents of intergalactic space. Definitions and usage vary and similar terms include the cosmos, the world and nature...

 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.

Peter Lynds
Peter Lynds
Peter Lynds is a New Zealander who first drew attention in 2003 with the publication of a physics paper about time, mechanics and Zeno's paradoxes....

 has recently 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
Second law of thermodynamics
The second law of thermodynamics is an expression of the tendency that over time, differences in temperature, pressure, and chemical potential equilibrate in an isolated physical system. From the state of thermodynamic equilibrium, the law deduced the principle of the increase of entropy and...

 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.

See also


  • Abhay Ashtekar
    Abhay Ashtekar
    Abhay Vasant Ashtekar is an Indian theoretical physicist. He is the Eberly Professor of Physics and the Director of the Institute for Gravitational Physics and Geometry at Pennsylvania State University. As the creator of Ashtekar variables, he is one of the founders of loop quantum gravity and its...

  • Anthropic principle
    Anthropic principle
    In astrophysics and cosmology, the anthropic principle is the philosophical argument that observations of the physical Universe must be compatible with the conscious life that observes it. Some proponents of the argument reason that it explains why the Universe has the age and the fundamental...

  • Martin Bojowald
    Martin Bojowald
    Martin Bojowald is a German physicist who now works on the faculty of the Penn State Physics Department, where he is a member of the Institute for Gravitation and the Cosmos. Prior to joining Penn State he spent several years at the Max-Planck Institute for Gravitational Physics in Potsdam, Germany...

  • Loop quantum gravity
    Loop quantum gravity
    Loop quantum gravity , also known as loop gravity and quantum geometry, is a proposed quantum theory of spacetime which attempts to reconcile the theories of quantum mechanics and general relativity...

  • Supernova
    Supernova
    A supernova is a stellar explosion that is more energetic than a nova. It is pronounced with the plural supernovae or supernovas. Supernovae are extremely luminous and cause a burst of radiation that often briefly outshines an entire galaxy, before fading from view over several weeks or months...

  • John Archibald Wheeler
    John Archibald Wheeler
    John Archibald Wheeler was an American theoretical physicist who was largely responsible for reviving interest in general relativity in the United States after World War II. Wheeler also worked with Niels Bohr in explaining the basic principles behind nuclear fission...

  • Astronomy portal
  • Space portal
  • Solar System portal

External links