The contravariant fourvector arising in special and general relativity,
(1)

where is the speed of light and is time. Multiplication of two fourvectors gives the spacetime interval
(2)
 
(3)
 
(4)

The contravariant fourvector arising in special and general relativity,
(1)

where is the speed of light and is time. Multiplication of two fourvectors gives the spacetime interval
(2)
 
(3)
 
(4)

Weisstein, Eric W. "Position FourVector." From MathWorldA Wolfram Web Resource. https://mathworld.wolfram.com/PositionFourVector.html