====== Units ======

<tabbox Intuitive> 

<note tip>
Explanations in this section should contain no formulas, but instead colloquial things like you would hear them during a coffee break or at a cocktail party.
</note>
  
<tabbox Concrete> 

  * **The International System of Units (SI)** - the modern metric system of measurement.
  * **Gaussian** - commonly used in electromagnetism.
  * **Heaviside-Lorentz (rationalized Gaussian)**
  * **Natural units** - commonly used in quantum electrodynamics and particle physics in general.

----

  * A great discussion can be found in Section 2.1 in Klauber's "Student-friendly Quantum Field Theory".
  * See also [[https://arxiv.org/pdf/1506.01951.pdf|BABEL OF UNITS]] by Neal J. Carron

----

Any physical quantity can be expressed by using as fundamental
unit either energy, mass, length or time. 

\begin{align}
ct&\approx \ell\Longrightarrow {\rm time}\approx{\rm length},\\
E&\approx mc^2\Longrightarrow {\rm energy}\approx{\rm mass},\\
E&\approx pv\Longrightarrow {\rm energy}\approx{\rm momentum},\\
Et&\approx \hbar\Longrightarrow {\rm energy}\approx{\rm (time)^{-1}}\approx
{\rm (length)^{-1}}.
\end{align}

 
<tabbox Abstract> 

<note tip>
The motto in this section is: //the higher the level of abstraction, the better//.
</note>

<tabbox Why is it interesting?>   



</tabbox>