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### Lorentz factor

The Lorentz factor *γ* is the factor by which time, length, and mass change for an object that is moving.

##### Explanation

The dimensionless Lorentz factor is defined as

where

vRelative velocity between inertial reference frames cSpeed of light

##### Alternative 1

The formula was originally described as

where

vSpeed cSpeed of light

##### Alternative 2

The formula can also be written as

where

βReduced speed

##### Alternative 3

The formula can also be written as

where

αContraction factor, which is the inverse of γ

##### Alternative 4

The formula can also be written as

where

tTime τProper time

##### Additional information

The Dutch physicist Hendrik Lorentz (1853 - 1928) is known for the Lorentz transformations.