## Invariant Mass

The **invariant mass**, **rest mass**, **intrinsic mass**, **proper mass,** or (in the case of bound systems or objects observed in their center of momentum frame) simply **mass,** is a characteristic of the total energy and momentum of an object or a system of objects that is the same in all frames of reference related by Lorentz transformations. In the center of momentum frame, the invariant mass of a system is simply the total energy divided by the speed of light squared. In other reference frames, the energy of the system increases, but system momentum is subtracted from this, so that the invariant mass remains unchanged.

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### Some articles on invariant mass:

**Invariant Mass**- Rest Energy

... conclusion about equivalence of energy and

**mass**... See background for

**mass**-energy equivalence ... hand, the concept of the equivalent Dirac

**invariant**rest

**mass**may be defined in terms of the self energy corresponding to the product of a geometric matter current and a generalized potential as part of a ...

... The rest

**mass**of a composite system is not the sum of the rest masses of the parts, unless all the parts are at rest ... The total

**mass**of a composite system includes the kinetic energy and field energy in the system ... p of the total momentum vector, the

**invariant mass**is given by In a mathematical system where c = 1, for systems of particles (whether bound or unbound) the total system ...

... when divided by the factor c2, where c is the speed of light) therefore gives the rest

**mass**(positive

**invariant mass**) of the system The

**invariant mass**of the system is actually ... Systems which have energy but zero

**invariant mass**(such as photons moving in a single direction, or equivalently, plane electromagnetic waves) do not have COM frames, because there is no frame which they have ...

... for single observers) in systems and in reactions between particles, but rest

**mass**(in the sense of being a sum of particle rest masses) may not be conserved through an ... for isolated systems and single observers, relativistic

**mass**is conserved (each observer sees it constant over time), but is not

**invariant**(that is, different observers see different values) ...

**Invariant mass**, however, is both conserved and

**invariant**(all single observers see the same value, which does not change over time) ...

**Invariant Mass**

... The

**invariant mass**is the ratio of four-momentum to four-velocity and is also the ratio of four-acceleration to four-force when the rest

**mass**is constant ...

### Famous quotes containing the word mass:

“All great art, and today all great artlessness, must appear extreme to the *mass* of men, as we know them today. It springs from the anguish of great souls. From the souls of men not formed, but deformed in factories whose inspiration is pelf.”

—Alexander Trocchi (1925–1983)