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Relativity

Lorentz factor

The multiplier applied to time, length and relativistic mass.

The Formula

gamma = 1 / sqrt(1 - v^2/c^2)

The multiplier applied to time, length and relativistic mass.

SymbolMeaning
gammaLorentz factor
vVelocity
cSpeed of light

What Each Symbol Means

gammaunitless

Lorentz factor

One at rest, and rising without limit near light speed.

vmetres per second

Velocity

The speed of the moving clock.

cmetres per second

Speed of light

299,792,458 metres per second.

See It Worked With Real Numbers

A formula on its own does not tell you which number goes where. The how to calculate time dilation page applies this equation to a concrete case, shows every intermediate step, and names the mistakes that produce a wrong answer even when the algebra is right.

Where This Formula Appears

This equation is the working core of How To Calculate Time Dilation, filed under Science. Every number the guide produces comes from substituting into this one line.