relativity intuition

Some conventions

We work with units such that the speed of light $c=1$

With spetial relativity, we are able to express events in carthesian coordinates : $[ct=t,x,y,z]$

We use superscript for indices : $x^0=ct=t$ and $x^3=z$ etc...

greek letter usage like this $x^μ$ means all spacetime coordinates, ie $μ=0,1,2,3$

latin letter usage like this $x^i$ means all spatial coordinates, ie $i=1,2,3$.