# Planck Units: Physics Beyond The Standard Model? [Review]

Updated: Mar 3, 2021

Author: Arpan Dey

[Symmetry Magazine. __https://www.symmetrymagazine.org/sites/default/files/styles/2015_hero/public/images/standard/FINAL_Planck_050516.jpg?itok=DtsrcMCq__.]

There are five fundamental constants in physics.

Manipulating the units of the above constants, we can find the ** Planck natural units**. These are the most fundamental units, and provide a rough idea about the value of the units during (or just after) the

**. The Planck natural units are essentially the limits of our physics today. For instance, the Planck length is significant because at shorter distances, quantum fluctuations allowed by the uncertainty principle disrupt the smooth geometry of space which is central to general relativity. On larger scales, quantum mechanics and general relativity independently describe different aspects of the physical reality. But at smaller scales, we don’t have the physics required to describe the physical reality, yet. Similarly, we need a theory that unifies quantum mechanics and general relativity to deal with time intervals smaller than the Planck time.**

*Big Bang*** Planck units** arise when effects of

**and**

*quantum field theory***, both, become considerable, i.e., get to the same order of magnitude.**

*general relativity*For ** massive-enough quantum objects**, general relativistic effects can’t be ignored. The particular mass at which this is achieved is the

**. The expression of the Planck mass can be determined by setting the**

*Planck mass***equal to the**

*Compton wavelength***. The Compton wavelength is integral to quantum field theory here. If a quantum particle of mass m travels through distances smaller than the Compton wavelength, then the energies get high enough to produce**

*Schwarzschild radius***out of vacuum. This is when quantum field theory enters the scene.**

*particle-antiparticle pairs*If a particle with momentum (linear) p moves through distances smaller than the ** de Broglie wavelength**, the particle must be described by quantum mechanics. To find out at what length scale both quantum mechanics and special relativity (which form integral parts of quantum field theory) becomes considerable, we set (m^2)(c^4) equal to (p^2)(c^2). [(E^2) = (m^2)(c^4) + (p^2)(c^2).]

All ** Planck quantities** are expressions in terms of

**. The full explanation of these phenomena and true experimentation on such conditions require physics beyond the**

*fundamental physical constants***, which has not yet been entirely achieved.**

*Standard Model**References*

*References*

Pretty Much Physics - YouTube. "Planck Scale | Where QFT and General Relativity Meet | Beyond the Standard Model". 2020.* *__https://youtu.be/la8v2nUSZ6M____.__