The Planck time is a unit of time that is defined by three of the fundamental constants of nature: Isaac Newton's constant of gravitation, G ; the velocity of light in vacuum, c ; and Max Planck's constant, h. These constants may be combined in one and only one way to give a quantity that has the dimensions of a time:
t planck = (Gh/c 5)1/2 = 1.3 × 10-43 s
This unit of time exists independently of all human standards of time measurement. It is defined by the gravitational, relativistic, and quantum aspects of the universe. The universe can be said to be "old" in the well defined sense that it is about 1060 Planck times in age (about thirteen billion years). The Planck time has cosmological significance. It marks the time before which the entire universe displays wave-particle duality. In order to understand events earlier than the Planck time, quantum cosmology is required. The Planck time was first identified by German theoretical physicist Max Planck (1858–1947) in 1899, although the idea of a natural unit of time based on the fundamental constants G, c, and e (the charge on the electron) was first presented by Irish physicist George Johnstone Stoney (1826–1911) in 1881.
See also Age of the Universe; Cosmology, Physical Aspects; Physics, Quantum
barrow, john. the constants of nature. london: jonathan cape, 2002.
john d. barrow
More From encyclopedia.com
Earth Sciences , There are several different ways that Earth scientists consider time. Geologic time is generally thought of as the period of time that begins with th… Standard Time , Standard time was introduced in 1884; it was the outcome of an international conference held in Washington, DC, to consider a worldwide system of sta… solar time , solar time,time defined by the position of the sun. The solar day is the time it takes for the sun to return to the same meridian in the sky. Local s… time zone , time zone One of 24 divisions of the Earth's surface, each 15° of longitude wide, within which the time of day is reckoned to be the same. At a confe… Time , Time Time is a dimension of our experience and our activity, but this dimension does not correspond to a simple physical reality. The concept of time… , and , eon 1. The largest geologic-time unit, incorporating a number of eras. The equivalent chronostratigraphic unit is the eonothem. Originally, two eons…
About this article
Updated About encyclopedia.com content Print Article
You Might Also Like