Planck time

Physical constant
Surname	Planck time
Formula symbol	${\displaystyle t_{\mathrm {P} }}$
Size type	time
value
SI	5.391 247 (60)e-44 s
Uncertainty  (rel.)	1.1e-5
Relation to other constants
${\displaystyle t_{\mathrm {P} }={\sqrt {\frac {\hbar G}{c^{5}}}}}$
Sources and Notes
Source SI value: CODATA 2018, direct link: NIST

The Planck time is a Planck unit and describes the smallest possible time interval for which the known laws of physics are valid. It results from the time that light needs to cover a Planck length and to effect a theoretical change in state. It was named after Max Planck .

However, this does not mean that time below Planck's time runs in discrete jumps. Only a quantum theory of gravity could answer whether time is discrete or continuous.

The Planck time therefore also defines the first point in time after the Big Bang , after the end of the Planck era, which can be physically described.

Derivation

For the Planck time , the following applies: ${\displaystyle t_{p}}$

${\displaystyle {\begin{aligned}t_{\mathrm {P} }&={\sqrt {\frac {\hbar G}{c^{5}}}}\\&\approx 5{,}391\,247(60)\cdot 10^{-44}\;\mathrm {s} .\\\end{aligned}}}$

The inaccuracy in the estimate is only caused by the other natural constants involved, but not by the formula itself.

This equation connects the three basic physical constants

• Gravitational constant , ${\displaystyle G}$
• Speed ​​of light , ${\displaystyle c}$
• reduced Planck's quantum of action . ${\displaystyle \hbar }$

The Planck time is therefore also a fundamental physical constant. The expression for results directly from the demand for a product of powers of , and , which has the dimension of a time. The same applies to the Planck length and the Planck mass , which together with the Planck time form the system of units that is expediently used in relativistic quantum theories . In 2010, the shortest experimentally reproducible time span (so far) was a time of 12 attoseconds (12 · 10 ⁻¹⁸  s), which is about 2 · 10 ²⁶ times the Planck time. ${\displaystyle t_{\mathrm {P} }}$ ${\displaystyle G}$ ${\displaystyle c}$ ${\displaystyle \hbar }$

Individual evidence

1. ↑ Harald Lesch and Harald Zaun : The shortest story of all life. Piper, 2nd edition, Munich 2008, section When the arrow of time was searching for a long way , ISBN 978-3-492-05093-7 , available on a website of Spektrum der Wissenschaft, last checked on May 3, 2013 ( Memento from February 26 2015 in the Internet Archive )
2. ↑ CODATA Recommended Values. National Institute of Standards and Technology, accessed July 8, 2019 .  Value for the Planck time.
3. ↑ " https://www.fv-berlin.de/index.php?id=61&L=0&tx_news_pi1 [news] = 39 & tx_news_pi1 [controller] = News & tx_news_pi1 [action] = detail" (article www.fv-berlin.de, accessed on January 1, 2015)