In the natural unit system, this quantity is equal to the square root of energy squared minus momentum squared. In a uniform gravitational field, the 
In the natural unit system, this quantity is equal to the square root of energy squared minus momentum squared. In a uniform gravitational field, the center of gravity for a linear system of particles is equal to the sum of this quantity for each particle times their distance from the origin over the total sum of this quantity. In 2012, CERN claimed to have confirmed the existence of the Higgs Boson or "god particle" that gives particles this property, which is equal to volume times density. For 10 points, name this quantity that differs from weight because it does not change depending on environment.
In the natural unit system, this quantity is equal to the square root of energy squared minus momentum squared.
mass