Planck acceleration: Difference between revisions
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'''Planck acceleration''' is the [[acceleration]] from [[rest (physics)|zero speed]] to the [[speed of light]] during one [[Planck time]]. It is a derived unit in the [[Planck units|Planck]] system of [[natural units]]. |
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#REDIRECT [[Planck units#Derived units]] |
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==Formula and value== |
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Planck acceleration may be stated as |
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{{block indent|<math>a_\text{P} = \frac{c}{t_\text{P}} = \frac{299792458 \ \text{m/s}}{5.39116 \times 10^{-44} \ \text{s}}</math>}} |
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{{block indent|<math>\approx 5.560815 \times 10^{51} \ \text{m/s}^2</math>}} |
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{{block indent|<math>\approx 5.670453 \times 10^{50} \ g</math>}} |
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where ''a''<sub>P</sub> is the Planck acceleration, ''c'' is the speed of light, ''t''<sub>P</sub> is the Planck time<ref>[http://physics.nist.gov/cgi-bin/cuu/Value?plkt "CODATA Value: Planck time"]. The NIST Reference on Constants, Units, and Uncertainty. US National Institute of Standards and Technology. June 2015. Retrieved 2016-07-24.</ref> and ''g'' is the [[standard acceleration of gravity]].<ref>[http://physics.nist.gov/cgi-bin/cuu/Value?gn "CODATA Value: standard acceleration of gravity"]. The NIST Reference on Constants, Units, and Uncertainty. US National Institute of Standards and Technology. June 2015. Retrieved 2016-07-28.</ref> |
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==Meaning== |
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The Planck acceleration is the highest acceleration conceivable in the Universe, as the speed of light is the highest possible speed and the Planck time is the shortest possible duration of any meaningful physical process.{{Citation needed|date=December 2019}} This limitation does assume that relativity has natural units. However, it is not clear whether any object in the Universe actually reaches or can reach the Planck acceleration. One event where the Planck acceleration was possibly reached was the [[Big Bang]], in regard to the acceleration of the expanding Universe during the [[Planck epoch]].{{Citation needed|date=December 2019}} Also, within a [[black hole]], such acceleration might be possible beyond its horizon, but that is certainly unknown (and what lies beyond a horizon is beyond the reach of physical observation). |
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In a classical description, [[photon]]s emanating from their subluminal source (for example, a [[annihilation|particle-antiparticle collision]]) experience zero acceleration, as they always travel at the speed of light. However, since the [[Planck time]] is the least conceivable delay,{{Citation needed|date=December 2019}} the "instantaneous" production of a photon pair can not be distinguished from the acceleration of a photon from zero to the speed of light in a [[Planck time]], thereby achieving a Planck acceleration. In other words, nothing higher than the Planck acceleration can be measured, since that would imply measuring a time interval shorter than the [[Planck time]].{{Citation needed|date=December 2019}} |
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As with other quantities at the Planck scale, the physics of the Planck acceleration are not yet fully understood.{{Citation needed|date=December 2019}} |
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If the mass of the body is given, then a second limit, Caianiello's maximal acceleration, also applies:<ref>{{Cite book|doi=10.1007/88-470-0472-1_10|arxiv=quant-ph/0407115|chapter=Caianiello's Maximal Acceleration. Recent Developments|title=Imagination and Rigor|pages=119–132|year=2006|last1=Papini|first1=Giorgio|isbn=88-470-0320-2}}</ref> |
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{{block indent|<math>a_\text{Caianiello} = \frac{2 m c^{3} }{\hbar}</math>}} |
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If the length ''L'' of the body is given, another limit exists on the acceleration that can be supported<ref>{{cite journal|doi= 10.1119/1.13372|title= Limitation on proper length in special relativity|journal= American Journal of Physics|volume= 51|issue= 10|pages= 889|year= 1983|last1= Taylor|first1= Edwin F.|last2= French|first2= A. P.|bibcode= 1983AmJPh..51..889T}}</ref> |
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{{block indent|<math>a_\text{Max} = \frac{c^2}{L}</math>}} |
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==See also== |
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*[[Planck units]] |
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*[[Orders of magnitude (acceleration)]] |
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==References== |
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{{Reflist}} |
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{{Planck's natural units}} |
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[[Category:Units of acceleration]] |
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[[Category:Planck units]] |
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Revision as of 11:18, 12 May 2020
Planck acceleration is the acceleration from zero speed to the speed of light during one Planck time. It is a derived unit in the Planck system of natural units.
Formula and value
Planck acceleration may be stated as
where aP is the Planck acceleration, c is the speed of light, tP is the Planck time[1] and g is the standard acceleration of gravity.[2]
Meaning
The Planck acceleration is the highest acceleration conceivable in the Universe, as the speed of light is the highest possible speed and the Planck time is the shortest possible duration of any meaningful physical process.[citation needed] This limitation does assume that relativity has natural units. However, it is not clear whether any object in the Universe actually reaches or can reach the Planck acceleration. One event where the Planck acceleration was possibly reached was the Big Bang, in regard to the acceleration of the expanding Universe during the Planck epoch.[citation needed] Also, within a black hole, such acceleration might be possible beyond its horizon, but that is certainly unknown (and what lies beyond a horizon is beyond the reach of physical observation).
In a classical description, photons emanating from their subluminal source (for example, a particle-antiparticle collision) experience zero acceleration, as they always travel at the speed of light. However, since the Planck time is the least conceivable delay,[citation needed] the "instantaneous" production of a photon pair can not be distinguished from the acceleration of a photon from zero to the speed of light in a Planck time, thereby achieving a Planck acceleration. In other words, nothing higher than the Planck acceleration can be measured, since that would imply measuring a time interval shorter than the Planck time.[citation needed]
As with other quantities at the Planck scale, the physics of the Planck acceleration are not yet fully understood.[citation needed]
If the mass of the body is given, then a second limit, Caianiello's maximal acceleration, also applies:[3]
If the length L of the body is given, another limit exists on the acceleration that can be supported[4]
See also
References
- ^ "CODATA Value: Planck time". The NIST Reference on Constants, Units, and Uncertainty. US National Institute of Standards and Technology. June 2015. Retrieved 2016-07-24.
- ^ "CODATA Value: standard acceleration of gravity". The NIST Reference on Constants, Units, and Uncertainty. US National Institute of Standards and Technology. June 2015. Retrieved 2016-07-28.
- ^ Papini, Giorgio (2006). "Caianiello's Maximal Acceleration. Recent Developments". Imagination and Rigor. pp. 119–132. arXiv:quant-ph/0407115. doi:10.1007/88-470-0472-1_10. ISBN 88-470-0320-2.
- ^ Taylor, Edwin F.; French, A. P. (1983). "Limitation on proper length in special relativity". American Journal of Physics. 51 (10): 889. Bibcode:1983AmJPh..51..889T. doi:10.1119/1.13372.