Lorentz factor converter
Convert a speed into its Lorentz factor, and see how much time slows and length contracts at that speed.
That's about the same as 90% of light speed. A year aboard would be about 2.294 years back home.
What it means
How relativistic is that?
These are the effects for steady motion in a straight line. Acceleration and gravity add their own, which is general relativity rather than special.
Every unit
Your speed in every unit
Learn
Three things worth knowing
-
γ = 1 ÷ √(1 − v²/c²)
At 0.5c that is 1.15, at 0.9c it is 2.29, at 0.99c it is 7.09. The curve is almost flat until it suddenly is not.
-
GPS has to correct for it
Satellite clocks run 7 microseconds a day slow from their speed, and 45 fast from weaker gravity. Without both corrections, positions would drift by 10 km a day.
-
Everyday speeds do nothing
At airliner speed gamma is 1.0000000000004. A round-the-world flight gains you a few hundred nanoseconds, which has been measured but will not keep you young.
Shortcuts
Popular speed conversions
Background
About the Lorentz factor
Gamma is the number everything in special relativity is multiplied by. At everyday speeds it is 1.000000000001 and nothing happens. At 90% of light speed it is 2.29: clocks run 2.29 times slower and lengths shrink to 44%.
It also sets the energy cost: reaching 0.9c takes 1.29 times the rest energy, and reaching c would take infinite energy.