- Planck epoch
physical cosmology, the Planck epoch (or Planck era), named after Max Planck, is the earliest period of timein the history of the universe, from zero to approximately 10-43 seconds (one Planck time), during which quantum effects of gravitywere significant. One could also say that it is the earliest moment in time, as the Planck time is perhaps the shortest possible interval of time, and the Planck epoch lasted only this brief instant. At this point approximately 1.37×1010 years ago the force of gravity is believed to have been as strong as the other fundamental forces, which hints at the possibility that all the forces were unified. Inconceivably hot and dense, the state of the universe during the Planck epoch was unstable or transitory, tending to evolve, giving rise to the familiar manifestations of the fundamental forces through a process known as symmetry breaking. Modern cosmology now suggests that the Planck epoch may have inaugurated a period of unification or Grand unification epoch, and that symmetry breaking then quickly led to the era of cosmic inflation, the Inflationary epoch, during which the universe greatly expanded in scale over a very short period of time.
As there presently exists no widely accepted framework for how to combine
quantum mechanicswith relativistic gravity, science is not currently able to make predictions about events occurring over intervals shorter than the Planck timeor distances shorter than one Planck length, the distance light travels in one Planck time—about 1.616 × 10-35 meters. Without an understanding of quantum gravity, a theory unifying quantum mechanics and relativistic gravity, the physics of the Planck epoch are unclear, and the exact manner in which the fundamental forces were unified, and how they came to be separate entities, is still poorly understood. Three of the four forces have been successfully integrated in a common framework, but gravity remains problematic. If quantum effects are ignored, the universe starts from a singularity with an infinite density. This conclusion could change when quantum gravity is taken into account. String theoryand Loop quantum gravityare leading candidates for a theory of unification, which have yielded meaningful insights already, but work in Noncommutative geometryand other fields also holds promise for our understanding of the very beginning.
Experiments exploring this time
Experimental data casting light on this cosmological epoch has been scant or non-existent until now, but recent results from the
WMAPprobe have allowed scientists to test hypotheses about the universe's first trillionth of a second (although the cosmic microwave backgroundradiation observed by WMAP originated when the universe was already several hundred thousand years old). Although this interval is still orders of magnitude longer than the Planck time, other experiments currently coming online including the IceCubeneutrino detector and the Planck Surveyorprobe, promise to push back our 'cosmic clock' further to reveal quite a bit more about the very first moments of our universe's history, hopefully giving us some insight into the Planck epoch itself. Of course, data from particle accelerators provides meaningful insight into the early universe as well. Experiments with the Relativistic Heavy Ion Colliderhave allowed physicists to determine that the Quark-gluon plasma(an early phase of matter) behaved more like a liquid than a gas, and the Large Hadron Colliderat CERNwill allow us to probe still earlier phases of matter, but no accelerator (current or planned) will allow us to probe the Planck scaledirectly. However, the more we understand about how matter forms, the more precisely we will be able to interpret what we learn from astrophysical data, and from other sources.
Timeline of cosmology
Unified field theory
* [http://csep10.phys.utk.edu/astr162/lect/cosmology/planck.html The Planck Era] from U of Tennessee Astrophysics pages
* [http://zebu.uoregon.edu/~imamura/209/apr5/planck.html The Planck Era] from U of Oregon Cosmology pages
* [http://www.astronomycafe.net/anthol/planck.html The Planck Era] by Sten Odenwald from Astronomy Cafe
* [http://www.site.uottawa.ca:4321/astronomy/index.html#Planckera The Planck Era - definition] from U of Ottawa's Astromomy Knowledge Base
Wikimedia Foundation. 2010.
Look at other dictionaries:
Planck epoch — noun The period immediately after the Big Bang, typically viewed at around one Planck time, whereby all forces were unified. Syn: Planck era … Wiktionary
Planck units — are units of measurement named after the German physicist Max Planck, who first proposed them in 1899. They are an example of natural units, i.e. units of measurement designed so that certain fundamental physical constants are normalized to 1. In … Wikipedia
Planck scale — In particle physics and physical cosmology, the Planck scale is an energy scale around 1.22 × 1028 eV (which corresponds by the mass–energy equivalence to the Planck mass 2.17645 × 10−8 kg) at which quantum effects of gravity become strong. At… … Wikipedia
Planck (disambiguation) — Max Planck was one of the most important German physicists of the late 19th and early 20th century, and is considered to be the founder of quantum theory.Planck may also refer to: * Planck s law of black body radiation * Planck s constant *… … Wikipedia
Planck era — noun Planck epoch … Wiktionary
Max Planck — Planck redirects here. For other uses, see Planck (disambiguation). Max Planck Born April 23, 1858( … Wikipedia
Grand unification epoch — In physical cosmology, assuming that nature is described by a Grand unification theory, the grand unification epoch was the period in the evolution of the early universe following the Planck epoch, in which the temperature of the universe was… … Wikipedia
Quantum gravity epoch — In physical cosmology, the quantum gravity epoch is the first era in the history of the Universe according to the standard Big Bang cosmology. In this era, the effects of quantum gravity such as fluctuating topology of space are commonplace. The… … Wikipedia
Timeline of the Big Bang — Physical cosmology Universe · Big Bang … Wikipedia
Cosmological decade — A cosmological decade ( CÐ ) is a division of the lifetime of the cosmos. The divisions are logarithmic in size, on base 10. Each successive cosmological decade represents a ten fold increase in the total age of the universe. As expressed in… … Wikipedia