# Squared length of 4-momentum g(p,p)?

#### berlinspeed

Problem Statement
Can someone explain why the squared length of p^2 = p dot p = -m^2 and not -m^2*c^2?
Relevant Equations
p^2 = p dot p = -m^2
Explained in statement.

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#### Gaussian97

That depends on two things:
1. What is the metric you use

2. What are the units you are using.

#### PeroK

Homework Helper
Gold Member
2018 Award
Problem Statement: Can someone explain why the squared length of p^2 = p dot p = -m^2 and not -m^2*c^2?
Relevant Equations: p^2 = p dot p = -m^2

Explained in statement.
In "natural" units we have $c=1$. See, for example:

"Squared length of 4-momentum g(p,p)?"

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